THE TOXICITY OF COMBINATIONS OF NICOTINE, UNDER MICHIGAN CONDITIONS, TO THE TREE AND TO THE CODLING MOTH, Carpocapsa pomonella. Linn. THESIS Submitted to the faculty of Michigan State College for the partial fulfillment of the degree of Doctor of Philosophy. J. M. Merritt 1936 ProQuest Number: 10008385 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10008385 Published by ProQuest LLC (2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 - 1346 INTRODUCTION The development of codling moth sprays in Michigan. The limitations of arsenical insecticides. LITERATURE REVIEW The nicotine-oil combination. Nicotine tannate. Fixed nicotine compounds. EXPERIMENTAL THEORY AND OBJECTIVES EXPERIMENTAL PROCEDURE Experiments in 1934 Experimental conditions. Experimental methods and materials. Environmental conditions. Results. The effect on foliage. The effect on fruit. Codling moth control. Relative control, Yellow Transparent. Relative control, Wealthy. Relative control, McIntosh. Relative control, Jonathan. Discussion of relative control. Summary. Experiments in 1935 Changes in procedure. Experimental conditions. Experimental methods and materials. Results. Nicotine deposition. The effect on foliage. The effect on fruit, color. The effect on fruit, dropping. The effect on photosynthesis. Relative effect, all types. Additional injury to fruit. Codling moth control. Population conditions. Relative control, on McIntosh. Statistical significance of differences in control. Control of deep entries. Statistical significance of differences in control. Relation of nicotine deposit to control. Corroborative results on Baldwin, Spy, and Ben Davis Discussion of relative control. Summary. CONCLUSIONS INDICATED BY EXPERIMENTAL RESULTS. SUMMARY 105399 INTRODUCTION "The codling moth destroys annually more than the State Agricultural College has cost, from first to last, and will, unless checked, destroy enough in 1 0 years to pay for our State Capitol." - S e c ?y Thompson in Proc. Mich. Pom. Soc., 1874, p. 152. The Development of Codling Moth Sprays in Michigan. The codling moth, Carpocapsa pomonella. attained the status of a major factor in apple production in Michigan about 1871, (l)* and since then efforts toward its control have never ceased. In 1880 liquid insecticides were used to protect the fruit by A. J. Cook (6 ), who applied two sprays of London purple on May 25 and June 20, and achiev­ ed complete control. Paris green, aceto-arsenite of copper, used since 1876 for control of canker worm (4) was also suggested by him, in view of its use the previous season by J. S. Woodard at Lockport, New York, with excellent results. Spraying was in general use by 1890 (5) and is still considered the only effective protection against codling moth damage. The schedule was enlarged about 1903 (33) to include summer applications against the second genera­ tion of codling moth. At the same time Pettit (33) men­ tioned the use of lead arsenate (17) for codling moth control, and cautioned growers against its adhesive proper­ ties, but the material by 1910 (15) was in general use. The Limitations of Arsenical Insecticides. Lead arsenate has maintained its position as a satisfactory codling moth insecticide, but the adhesive properties responsible for * Numbers in parenthesis refer to literature cited. - 2 - this finally created the problem which Pettit (loc. cit.) may have anticipated, namely the removal of harmful resi­ dues before consumption of the fruit. The toxicity of arsenical residues was considered in the federal food and drugs act of 1906 (8 ), and a limit designated, but no serious problem existed until about 1926. By this time codling moth control in arid districts required repeated applications, and resulted in harvested fruit with many times the limit of arsenical residue, together with lead residues considered deleterious to public health. Federal tolerances necessitated the removal of these residues, or the substitution of insecticides which would leave no harm­ ful residues at harvest. The increased cost of control with lead arsenate due to residue removal permitted more general recommendation of nicotine sulfate combinations for codling moth control, previously considered too expen­ sive (26), and instigated a critical study of this material. LITERATURE REVIEW Nicotine * is an alkaloid insecticide which was first marketed In 1885 as Gold Leaf Tobacco Extract (16). It was used as a contact spray, often In combination with arsenicals, to control orchard pests, other than the codling moth. Nicotine, as a sulfate containing 40$ of nicotine, was first tested for codling moth control by De Sellem (7) in * Nicotine, C 1 0 H 1 4 N 2 , is the poisonous constituent "of" the tobacco plant, in which it exists in combination with malic and citric acids. It is a colorless, oily liquid soluble in water - - -. It rapidly oxidizes in contact with the air— . Organic Chemistry, Bernthsen and Sudborough, P. 590. 1930. - 3 - Washington in 1915 and 1916. It was subsequently tested in several states, including Michigan (30), where it was applied alone, or in combination with soap or lead arsen­ ate with results which were somewhat erratic (27) though indicative of possible control* The Nicotine-Oil Combination* Nicotine sulfate was first used in combination with oil (distillate emulsion) by Foster and Jones (21) for the control of pear thrips in California. Experiments in codling moth control in 1927 and 1928 were reviewed by Herbert and Leonard (26) and included tests of nicotine sulfate alone or in combination with casein spread­ ers or summer oil emulsions. Le Sellem (26) obtained results with oil and nicotine which surpassed those of the arsenate of lead tests in 1927. In 1928 workers in Washington, Oregon and Idaho tested oil, nicotine and a combination of the two, and found inferior control with either used alone, but control comparable to the lead arsenate treatment when combined (26, 29). Newcomer and Yothers in 1928 and 1929 (32) found nicotine sulfate an effective ovicide at a concentration of 1-800, and obtained good results in field experiments with a combina­ tion of nicotine sulfate 1-1600 and emulsified oil. They appreciated the necessity for retarding the volatilization of the nicotine to retain its toxicity long enough to act as an effective ovicide and larvicide for codling moth. They also tested sodium bisulfate, aluminum sulfate, glycerine and corn syrup with nicotine sulfate, none of which was as successful as the oil-nicotine combination. Newcomer and ^others (loc. — 4 — cit. p. 24) analyzed the sprayed foliage for percentage of nicotine to study the duration of its activity, and studies on the use of oil-nicotine in the northwest by Leonard (18) during the same season included this work, although published first. The method of analyzing the sprayed foliage for persisting nicotine has since been a valuable index, and will be referred to subsequently. Since 1930, when it was first tested by the Michi­ gan State College Agricultural Experiment Station, the combination of oil and nicotine sulfate has ordinarily been accepted as a satisfactory substitute for lead ar­ senate in codling moth control, with the limitation that it must be applied more often (14) to counteract the volatilization. This condition has stimulated research for a combination which would retain toxicity long enough to permit correlating the renewal with the growth of the apple, as in the case of lead arsenate. To effect this, the volatilization must be extended 4 to 6 days longer than the oil and nicotine combination permits* Nicotine Tannate. Nicotine tannate was prepared by J. M. Ginsburg in an attempt to develop nicotine as a stomach poison (24). This material was used to control codling moth in 1929 by Headlee, Ginsburg and Filmer in New Jersey (24), also by Newcomer and lothers(32) in the Pacific Northwest. These experiments and later tests in New Jer­ sey by Filmer (18) and Driggers and Pepper (10), and in Michigan by Hutson (20) indicate a toxicity and resultant codling moth control approximating the nicotine sulfate- - summer oil combination. 5 - No effective retention of toxi­ city for more than 1 0 days is shown by the analyses of applications (32, 18) and the occasional injury to the fruit and considerable discomfort to the men using the material (2 0 ) has reacted against its general adoption. Fixed Nicotine Compounds* Driggers and Pepper (10), in testing nicotine tannate in New Jersey, found a signifi­ cant reduction in codling moth injury in the plot which received bentonite sulfur as a fungicide, and also ob­ tained better results with nicotine sulfate and benton­ ite sulfur, or bentonite and soap, than with lead arsen­ ate (ll). They attribute to bentonite the property of Hfixing!T nicotine and point out the remarkably adhesive properties of bentonite-sulfur (ll), and the marked increase in retention of nicotine, as shown by their an­ alyses, was apparently due to these factors. Nearly twice as much nicotine was retained on the block receiv­ ing nicotine tannate and bentonite sulfur as on that sprayed with nicotine tannate alone. The toxicity to codling moth was also prolonged, as indicated by their laboratory tests. EXPERIMENTAL THEORY AND OBJECTIVES Michigan conditions justify the development of a codling moth insecticide which obviates the necessity of residue removal at harvest. The harvest period extends from mid-summer to late fall, and large quantities of fruit are moved by truck during this time, either to market or terminal storage facilities. The inclusion of residue re- - 6 - ipoval is not compatible with the marketing practice of many growers. Many prefer to use an arsenical substitute in their spraying program than to attempt residue removal from early varieties, or to invest in removal equipment for fall varieties. It is well known that environmental changes affect insecticides as well as insects, and the established practice is to determine the local reactions of new insecticidal measures before their general recommendation. These factors, therefore, were responsible for a pro­ gram of studying, in Michigan, the various nicotine combina­ tions elsewhere shown toxic to the codling moth and of devel­ oping a treatment suitable to our conditions. Materials were available for studying the effect of retention of nicotine in insoluble and non-volatile forms on codling moth control, in comparison to the soluble and volatile nicotine sulfatesummer oil combination. All experiments were to be compared with the control achieved by the lead arsenate schedule re­ commended for that area. Another effect which must always be considered in test­ ing insecticides is that of repeated applications of the ma­ terial to the tree. varietal differences. This is further complicated by profound The various constituents of an insecti­ cide must be relatively harmless to the fruit and foliage, not only individually, but in combination. It was, therefore, intended to compare any manifestations of fruit or foliage injury resulting from the experimental schedules. - 7 - EXPERIMENTAL PROCEDURE Extremely variable weather conditions in 1934 and 1935, as well as changes in materials and schedules result­ ing from experience during 1934, necessitate the presenta­ tion of each year’s experiments separately, *>ata from many points in the country were considered before the program for 1935 was assembled, and influenced the modification of materials apparently satisfactory here in 1934. EXPERIMENTS IN 1934 The following experiments were designed to determine the relative value of nicotine sulfate in combination with bentonite, bentonite-sulfur, and summer oil in controlling a heavy codling moth infestation in a well managed commercial orchard. All tests were compared with the lead arsenate schedule as recommended by the Michigan State College Agricul­ tural Experiment Station for this area. In addition to the insecticidal efficiency, data were desired on the relative toxicity of the schedules to the fruit and foliage. Experimental Conditions. The orchard in which these experi­ ments were conducted is located ten miles from Benton Harbor, in Berrien County, and is owned by C. C, Kniebes. In this area there are normally two full broods of codling moth, and the mean yearly rainfall is 32.31 inches. The location is exceptionally well suited for apple production. A large proportion of this area is devoted to summer apple production, and the majority of this fruit is marketed in Chicago, often delivered by truck. Removal of residues is not readily adapt­ ed to these varieties, nor to the marketing practices. - 8 - Efforts to keep arsenical and lead residues within estab­ lished tolerances by curtailing applications, particularly on summer varieties, had permitted the development of a codling moth population of epidemic proportions in many orchards by the season of 1933. The experimental plots were located in a block of twenty-three year old trees, and included McIntosh, Jonathan, Wealthy, Yellow Transparent and a few trees of Gr imes Golden varieties. The orchard is planted in a strong, heavy soil, and the trees have been maintained in excellent vigor for many years. An index to the population of codling moths present was afforded by examination of the corrugated paper bands, treat­ ed to kill larvae pupating in them, which had been placed on the trees in 1933, after the loose bark under which pupation normally occurs had been removed. One hundred bands, taken at random from trees which had borne a crop in 1933, were found to contain an average of 150 larvae per band. A fur­ ther index of the population is afforded by the catch of moths in pots containing an attrahent which were hung in several trees in 1934. The number of moths recorded from these pots during the peak flight on June 1st and 2 nd averaged slightly over 50 for each of nine pots on each day. Experimental Methods and Materials. The equipment available for application of the experimental schedules consisted of a horse-drawn John Bean Company sprayer, capable of delivering about twelve gallons per minute with a pressure of 225 to 300 pounds. - 9 - The method of application deferred somewhat to the limitations of the equipment, hut entirely satisfactory coverage of the trees was obtained by the use of two single nozzle spray guns* One operator sprayed from the ground, assuming responsibility for coverage on the lower half of the trees, and the entire inside portion. The other meanwhile completed the upper portion, working from the top of the sprayer. This method was considered the best way of covering some of the largest trees, spreading as much as 56 feet, and pruned wide and flat at the top. The rate of application was increased as the foliage de­ veloped, with a maximum application of about 55 gallons per tree on the largest varieties, and an average of 20 gallons throughout the season. The six experimental schedules used are outlined in Table I. TABLE I CODLING MOTH PROJECT KNIEBES ORCHARD, BERRIEN COUNTY MICHIGAN 1934 Schedule of Cover Sprays 1 st Brood: 2nd Brood: Kolofog, 6 #; B. L. 40, J pt.; S.A.s*, 2 #. B. L. 155, 5#; 14 day interval. 1 st Brood: 2nd Brood: Flotation sulfur, 5#; B. L. 155, 5#. B. L. 40, J- pt.; Orthol-K, \ gal., or B. L. 155, 3#. 7 day interval. 1st Brood: 2nd Brood: B. L. 155 BX, 3#; Orthol-K, 1 B. L. 155 BX, 3#; Orthol-K, J 1 0 day interval. 1 st Brood: 2nd Brood: B. L. B. L. 1 st Brood: 2nd Brood: Lead arsenate, 3#: Lime, 4#. Same 10-14 day interval. 1 st Lead arsenate, 3#; Lime, 4#: B # L. 40, 1 pt. 7 day interval. Brood: gal. in peak. gal. 155 BX, 5#; Orthol-K, \ gal. in peak. 155 BX, 5#; 14 day interval. - 31 - - In testing various insecticide combinations for cod­ ling moth control, it is customary to maintain a uniform treatment of all trees throughout the pre-blossom period, and usually the calyx spray is common to all, as in this instance, lead arsenate and lime sulphur being indicated for all plots. In the first cover spray, ten days later, lead arsenate was used throughout but the fungicide, ex­ cept on schedule 4, was changed to flotation sulfur. The materials tested in the schedules for first brood control should be described. ^ test of bentonite sulfur, nicotine sulfate, and sulfo-ammonium soap was included, this being one of the most successful in New Jersey experi­ ments. (10, ll). The bentonite sulfur used is manufactur­ ed by the Niagara Sprayer and Chemical Company, under the name of "Kolofog." According to Doane (9), f,It is a colloidal sulfur obtained by fusing the colloidal material bentonite with ground elemental sulfur. . .” '^he nicotine sulfate used in all cases was "Black Leaf 40,” manufactured by the Tobacco By-Products and Chemical Corporation. The schedule was designed to test bentonite nicotine sulfate (B. L. 155) with flotation sulfur (schedule 2), for a fungi­ cide is often necessary through most of the season, because of inefficient scab control in the pre-blossom sprays. B. L. 155 BX represents a minor variation from the bentonite-nicotine sulfate combination used in B # L # 155, pre­ sumably increasing its efficiency. The summer oil used in all schedules was Orthol-K medium, but the supply broke down on July 21, and Ansbacher medium was substituted until a fresh supply of Orthol-K could be obtained - 12 - on August 6 . The materials used subsequent to the first cover spray, together with the actual date of application, are included in Table II. -13TABLE II SPRAY SCHEDULE - KNIEBES ORCHARD - BERRIEN COUNTY, MICHIGAN 1934 Date Plot 1 Plot 2 Calyx 2 ( 15-18 May3# day 31 May 10 5# 3# 21 day 5 June 6# B. 28 day 1 2 June 6# B. 35 day 19 June 6# B. 45 day 28 June 6# B. 7 July 14 July 17 July 21 July 23 July 24 July 27 July 31 July 6 Aug. 13 Aug. 16 Aug. Aug. 27 Aug. 20 Plot 3 2 Gals.Lime Sul. 2 Gals.Lime Sul* 3# Lead A rsenate 3# Lead Arsenate 5# Flotation Sul. 3# Lead Arsenate 3# B. L. 155 BX .. 3 3# B. L. 155 BX Gal. simmer oil 1 3# B* L. 155 BX SECOND BROOD B. L. 155 BX " i pt. B. L. 40 3# B. L. 155 BX i Gal. summer oil b Gal. summer oil i pt. B. L. 40 § Gal. summer oil 3# B. L. 155 BX J Gal. summer oil *1 pt. B. L. 40 1 Gal. summer oil i pt. B. L. 40 5 Gal. summer oil All Yellow Transparent f pt . B. L. 40; f Gal. oil 3 # B. L. 155 BX i Gal. summer oil 3 # B. G. 155 3# B. L # 155 BX 3# B. L. 155 ** 5# B. L. 155 * J Gal. summer oil 3 # B. L. 155 3# B. L. 155 BX J Gal. summer oil 3 # B. L. 155 5# B. L. 155 3# B. L. 155 BX 3# B. L. 155 J Gal. summer oil 5# * Ansbacher oil substituted for Orthol-K; burning on previously uninjured Grimes. Delayed from 21st because of high temperatures. *** B. L. 155 substituted for oil-nicotine to prevent further injury to leaves burned by sulfur spray. ** Orthol-K, fresh supply, substituted for the Ansbacher. * -143?ABLE II (Cont Td) Bate Plot 4 Plot 5 Plot 6 Calyx 2 Gals, Lime Sul. 2 Gals. Lime Sul 15-18 May 3# Lead Ar senate 3# Lead Arsenate 2 Gals.Lime Sul. 3# Lead Arsenate 10 day 31 May 2 Gals. Lime Sul. 5# Flotation Sul 3# Lead A r senate 3# Lead ArSenate 5# Flotation Sul. 3# Lead A rSenate 21 day 5 J line 5# B. L. 155 BX 8 June 28 day 12 June 3# Lead A rSenate 4# Lime;l pt.B.L.40 5# B. L. 155 BX 3# Lead Arsenate f Gal. summer oil 4# Lime 3# Lead Ar senate 4r Limejl pt.B.L.40 15 June 35 day 19 June 5# B. L. 155 BX 3# Lead Arsenate 4# Lime;l pt.B.L.40 22 June 3# Lead Apsenate 4# Lime 25 June 45 day 28 June 5# B. L. 155 BX 3# Lead ArSenate 4# Limejl pt.B.L.40 29 June 3 July 7 July 16 July 23 July 24 July 28 July 6 Aug. 9 Aug. 20 Aug. 23 Aug. SECOND BROOD 3# Lead Arsenate 4# Lime 5# B. L. 155 BX 3# Lead Arsenate 4# Lime 5# B. L. 155 BX All Yellow Transparent f pt. B. E. 4 0 , f Gal. oil 3# Lead Arsenate 4# Lime 5# B. L. 155 BX 3# Lead Arsenate 4# Lime 5# B. L. 155 BX 3# Lead Arsenate 4# Lime - 15 - The schedules were applied to plots containing nine trees each. Each treatment was replicated three times, making a total of 27 trees in three locations from which to take results* The replications were arranged in a modification of the Latin square of R. A. Fisher (19), described by Hartzell (23) as the best method to overcome heterogeniety in field tests. The available area did not permit six nine- tree plots, without jeopardizing the randomization. Further­ more, it was desirable to confine lead arsenate schedules to the fall varieties, or summer varieties which would stand washing to remove spray residues. The arrangement of plots in relation to the varieties and to each other is indicat­ ed on Figure I. - 16 - Fjgure 1 Location of Plots and Count Trees Kniebes* Orchard, Berrien Co., Mich. -------- —-- 1 ■ m m m nr m m m m m 3 m m m m m m 3 1 3 3 3 1 5 3 m m in m m m 3 3 3 3 3 1 m m m m m 3 3 3 3 3 6 3 6 m 4 r m m m m m 3 3 3 3 1 3 3 1 3 4 5 1 5 2 1 3 3 1 3 3 3 w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w 3 4 6 1 2 t t t t t t w w w w w w w w w t t t t t t _t t t t t t t t t t t t t t t t t 1 t S 3 t t t t t t t t t £ g g £ g g g. g g m .1 w t - McIntosh Jonathan Wealthy Yellow Trans­ parent g * Gpijnes x - Count Tree 0 - Plot Number - 17 Environment al Conditions. - Environmental character­ istics affect insecticides as well as insects, and under extreme conditions the effectiveness of the schedule may­ be impaired by severe injury to the tree, or by excess­ ive precipitation may be rendered ineffective. Seas­ onal conditions vary, making it necessary to consider the conditions under which the program was completed. In these experiments schedules were closely follow­ ed, both as to timing and concentration of ingredients. A certain amount of injury to the foliage is expected when a spray is applied in hot weather, and in an ex­ perimental program these effects must be studied in the critical range as often as possible, to determine the reaction under extreme conditions. Yet it must be remem­ bered that if such a temperature is reached only once in 50 years, no spray can be fairly expected to react normally, and a test then would be unfair, if a matter of twenty-four hours will bring normal temperatures. The data on daily temperature and rainfall are pre­ sented in Table III. These data were collected by the nearest U.S. Weather Bureau station, approximately three miles away. Temperature records vary little from those prevailing at the orchard, but precipitation occurred several times at the Weather Bureau station that did not reach the orchard. Table III. These occasions are noted in - 18 - TABLE III Temperature and Precipitation Records Coloma, Michigan, 1934 Date May July Aug. June Temp. Pre- Temp Temp. PrePrePre-cipi. Temp. Max. Min. cip. Max. Min. cip. Max. Min. cip. Max. Min. 50 104 52 97 50 3 99 4 65 91 5 61 94 6 53 81 7 55 81 8 50 94 50 1.15 8 8 9 10 62 T 85 38 85 11 12 31 76 48 .23 73 13 14 42 83 91 44 15 40 84 16 93 86 53 17 83 18 87 54 84 90 72 19 89 92 20 65 88 70 92 21 45 .72 75 22 83 93 41 73 23 .27 89 69 47 24 84 69 35 25 91 41 68 26 90 45 73 27 100 28 80 51 96 82 53 29 85 52 30 88 62 97 31 8 8 .3 Mean 77.9 50. 9 75 72 83 87 80 85 76 80 89 85 63 63 64 62 60 75 1 2 70 56 54 62 70 61 55 52 64 62 63 46 49 53 85 95 82 90 87 95 97 92 97 65 63 67 60 60 62 52 63 65 72 65 64 86 68 86 85 88 .2 66 61 62 60 55 .1 68 65 53 * . 2 2 52 62 *.17 62 70 67 66 74 *.08 64 60. 5 90 90 87 92 97 99 .12 *.07 97 95 85 95 90 84 95 100 *.08 62 68 60 60 65 75 101 72 106 71 77 101 70 107 75 106 76 103 67 96 *.06 85 63 84 58 58 74 60 90 94 53 91. 1 65. 0 59 72 *.18 62 61 67 65 *.18 66 * . 0 2 66 99 95 89 98 85 89 76 80 72 72 63 62 76 53 63 *.72 .08 65 63 86 65 95 64 1.08 84 52 71 80 50 78 64 54 79 55 .42 65 51 73 81 52 80 54 55 78 70 42 77 47 78 57 84.7 60. 3 Total 2.37 1.67 .54 2.68 Ave. (10 Yrs) 3.65 2.93 2.50 2.37 -1.28 Deficiency (at orchard) ■2.63 -2.38 -.79 * Indicates no precipitation at orchard. - 19 - Results. The Effect on Foliage. The extreme deficiency in mois­ ture did not have any serious effect on the fruit, for the soil was admirably suited to withstand drought, feather­ ing of spray material was also reduced to a minimum, for spray coverages were renewed immediately following any pre­ cipitation. The injury to foliage was less than might have been expected during the extremely hot periods, probably be­ cause of the low relative humidity which usually prevailed. The primary injury which occurred was related to abnormally high temperatures which prevailed very early in the season, when foliage was tender, or to poor drying conditions during periods of high temperature under the heavy foliage of some varieties. Secondary injury followed where toxic materials were permitted to enter lesions from the primary toxicant, and in many cases caused the abcission of these leaves. A study of the foliage injury resulting from these schedules was conducted. On June 27th the average number of leaves per spur from 300 spurs per plot was determined for each treatment. Wealthy and Jonathan varieties were select­ ed as being most susceptible to injury of the varieties pre­ sent (13). This gave a figure to be used as a base count. Counts were made on July 24th, September 11th, and October 1 2 th, by the same method and on the same trees. f rom these data the percentage of leaf fall per plot was computed as an index of the relative injury to the leaves which most affect the bearing qualities of the trees. Non-bearing spurs were used, because no new leaves were produced on these after the base count. Table IV. The results of these counts are included in - 20 - TABLE IV LEAF COUNTS - WEALTHY AND JONATHAN KNIEBES ORCHARD, BERRIEN COUNTY, MICH. 1934 Plot No. June 27 Leaves per twig July 24 fc-ent. 11 Leaves loss Leaves % loss per twig per twig Oct. 12 Leaves % loss per twig 1 8.11 7.52 7.3 6.00 26.0 6.01 26.0 2 8.29 7.69 7.2 6.15 25.8 6.07 26.8 3 7.93 7.73 2.5 6.52 17.8 6.47 18.4 4 7.75 7.79 2.1 6.32 18.5 5.74 26.0 5 8.09 7.88 2.6 6.24 22.9 5.37 33.6 6 8.03 7.51 6.5 5.96 25.8 5.70 29.0 *1 8.59 8.10 5.7 6.20 27.8 5.95 z> • o to 2 8.26 7.13 13.7 6.20 25.0 5.90 28.6 3 7.88 7.28 7.6 6.53 17.1 6.26 20.6 4 7.90 7.71 2.4 6.52 17.5 6.20 21.5 5 8.28 7.89 4.7 5.92 28.5 4.68 43.5 6* 8.31 7.73 7.0 5.38 35.3 4.07 51.0 Plots 1-6 Wealthy Plots^l- 6 *- Jonathan - 21 - Both plots receiving sulfur during the first brood show a considerable leaf fall by July 24th, more by Sep­ tember 11, then only normal loss. This was due to the ap­ plication of sulfur during the hot weather in June, par­ ticularly on June 28th, when the last application was made. This type of injury was most serious on those trees receiving flotation sulfur, as indicated by the result of the July 24th count on Jonathans. The injury on trees of the same variety receiving Kolofog surpassed that from flotation sulfur by September 1 1 th, because of injury re­ sulting from an application of one per cent summer oil (with nicotine) four weeks after the last application of Kolofog on July 2 1 st. This injury was typical of oil on sulfur, and indicated that the weathering of the bentonitesulfur had been inhibited by the drought, The injury was further complicated on both Plots 1 and 2 , receiving summer oil, by the fact that the penetration of oil through the leaf tissues injured by sulfur alone, caused them to fall. However, the primary injury by oil following bentonitesulfur was decisively illustrated by a few Grimes trees, previously uninjured by sulfur sprays, which were severely burned immediately following the oil application four weeks later. The flotation sulfur application of June 28th had weathered sufficiently by July 7th to permit the applica­ tion of one-half per cent oil (with nicotine) without in­ jury except the oil penetration through old lesions. Spec­ tacular leaf injury from sulfur and oil occurred on the new leaves of the new shoot growth, but is not indicated in "’able TV. -22Plots 3 and 4, receiving B. L. 155 BX (with oil in Plot 3, second brood) show the least leaf fall, and no Injury was observed during the spraying. The data in­ dicate a heavier leaf fall on Jonathans in Plot 3 by July 24th, probably due to the application of oil on the 16th, but no later injury is indicated. Plots 5 and 6 may be considered together, since the agent causing leaf fall was lead arsenate In both cases. Even though lime was added in both plots as a corrective against injury, the leaf fall, which is especially char­ acteristic of arsenical injury, surpassed that of any other schedule. This was particularly true during Sep­ tember, when the percentage of fallen leaves increased from 30 to nearly 50. It is interesting to note that the leaf fall continued from Plot 6 through the season, even though the applications ceased on June 29th. In summarizing, it may be said that little or no in­ jury resulted from applications of bentonite-nicotine, with or without summer oil. Applications of sulfur under existing weather conditions caused significant injury to the foliage, aggravated by any oil, because of penetration. In the case of bentonite-sulfur (Kolofog), residual sulfur caused primary oil-on-sulfur injury. Applications of lead arsenate caused foliage injury, with dropping, which in­ creased as the season advanced, apparently related to the amount applied in a given period, rather than any weather factor. fall. This was enhanced, doubtless, by the lack of rain­ -23|£he_ Effect on Fru i t s Spray injury to the fruit was con­ fined to that caused by sulfur applications during the hot weather. Beginning with the hot period during which the T!1 0 -dayTT application was made, a type of injury call­ ed t!sunscald,! was produced, not only in this orchard but in the whole region, whenever sulfur application preceded a hot period. In these experiments the n1 0 -dayn (after petal fall) application included 5# of flotation sulfur, except Plot 4, which received 2 gallons of liquid lime sulfur. The temperature during this application, on the 31st of May, was 97°Fahrenheit at the observation point three miles away. Some burning occurred on the foliage of McIntosh, Yellow Transparent, and other varieties. Fruit injury occurred on Yellow Transparent, Wealthy, and on Jonathan. Later injury developed on Yellow Transparent and Wealthy from applications during June, particularly the one made on June 28th, when the humidity was slightly higher than when previous applications were made at com­ parable temperatures. The injury to Wealthy included a stem end injury, causing many to drop before maturity, and injury to the exposed surface which caused the apples to crack. Lack of time prevented a count of fruit injury at harvest, but it was more apparent than significant. The harvest of Yellow Transparents, however, occurr­ ed shortly after the injury became apparent, and before it was masked by growth of the fruit. The pickers were instructed to remove all these apples with the first pick- -24ing. A certain proportion of injury was evident on all plots, due to the sulfur injury of May 31st, not exceed­ ing .6 $ in any case. Additional injury due to the later sprays, as indicated above, increased this as much as 2% on the plot receiving flotation sulfur. Codling Moth Control The data on relative control were obtained from trees selected for their uniformity of bearing. In most cases two trees were selected In each replication, and, as two varieties were included in each replication, one tree of each variety was chosen. The exact distribution of count trees is indicated in Figure I. All apples from each count tree were examined, and the number of clean or uninjured apples recorded. The apples showing codling moth injury were separated Into two classes, those having injuries caused by unsuccessful attempts of entering larvae, usually called shallow en­ tries or "stings," and those Injuries made by larvae suc­ cessfully escaping the spray film, usually called deep en­ tries or "worms." The apples removed during the thinning process were examined, but the injury was found to be negligible, and it was considered that the trees started on a uniform basis after they were thinned. After thinning was complete, all dropped fruit from the count trees was examined and scored for injury at regu­ lar intervals, the totals being included with those of the picked fruit. These data are presented in Table V. Schedule or -25plot numbers correspond with Table II* Data presented in this table include results from four varieties, but omissions of some treatments on early varieties make direct comparison of all schedules impossible. As stated previously, the lead arsenate schedules are mostly confined to the later ripening varieties, because of difficulty of residue removal from summer apples. -26- TABLE V CODLING MOTH INJURY PER CENT ENTRIES KNIEBES ORCHARD, BERRIEN CO. 1934 Plot No. 1. HARVEST DATE Type of Yellow T. Wealthy McIntosh Entry 17-31 July 22 Aug-5 Sept. 5 Sept. J onathan 1 2 Oct. Deep Shallow 1.70 4.47 3.53 16.25 14.83 . Deep Shallow .42 1.38 5.06 4.92 10.82 12.27 3. Deep Shallow 1.30 1.13 5.89 4.17 38.30 16.65 8.55 7.62 4. Deep Shallow 2.18 1.82 9. 64 5.19 45.83 12.50 8.85 10.67 5. Deep Shallow 3.43 3.76 43.03 24.07 4.09 19.87 6. Deep Shallow 5.76 2 Total examined 1.68 1.32 2.62 6.88 36.18 13.47 24.80 21.53 45,031 28,220 13,334 18,398 -27Extreme variation in the degree of control obtained on different varieties is outstanding. responsible for this. Three factors are Data presented here were collected over a period of three months, that is, counts were made on varieties harvested as the second brood codling moth was emerging, and continued at intervals until this brood was entering hibernation. During this time the codling moth population increased many fold, and the increased injury on successively ripening varieties reflects this. The factor of varietal susceptibility enters into the re­ sults obtained on McIntosh, known to be prone to heavy codling moth injury. In this case the effect was further aggravated by the fact that these extremely large trees, after three years of capacity crops of 30 to 35 bushels apiece, had set only one-third to one-half a crop. In an­ ticipation of this they had not been pruned, and the dense growth interfered with effective spraying, ^he count trees, however, could not be said to have failed to bear an aver­ age crop, though some of the other trees did. There being no striking contradictions in the control obtained, the variations in control serve to indicate the relative control under several conditions, and thus offset the disadvantage of being unable to collect the data from all varieties for direct comparison. Relative Control. Yellow Transparent. The harvest of Yellow Transparent occurred during the emergence of the second brood moths, and almost no second brood injury is -28included in data on this variety. Therefore, the first brood schedules may be evaluated by these data. Yellow Transparents are susceptible to codling moth injury, but the control obtained does not reflect this, ^he differ­ ences between plots are too small to be significant, but it must be admitted that the control was excellent, ^his was probably due to the fact that a seven day interval between sprays during the period of first brood emergence from June 5th to 19th was too short to demonstrate varia­ tions in materials applied. The retention of toxicity was more than seven days, though variations might have occurr­ ed under normal conditions of rainfall (28). There was no variation in size which could be correlat­ ed with the spray treatment, but variations in finish were apparent. The plot receiving Kolofog showed considerable residue and a rough finish, and the plot sprayed with flo­ tation sulfur and B. L. 155 showed, to a lesser degree, the same effect. The lead arsenate and B. L. 40 (nicotine sul­ fate) treatment had the best finish, though the finish on the B. L. 155 plot, having had two summer oil sprays with the B. L. 155, was nearly as good. very little *residue was apparent on the plot receiving five pounds of B. L. 155 BX. The results obtained in the harvest of the Yellow Transparents thus tend to indicate that the start of the second generation of codling moth found the plots nearly equal in control, and that later variations are due more to the second brood spray schedules than to the first. -29Relative Controls Wealthy. The next variety to be harvest­ ed was the Wealthy, bearing a heavy crop on relatively small trees. It is apparent that variation between the plots was developing, although the control had not suffered particular­ ly. Plot No. 1 , with B. L. 155 following Kolofog an<^ B. L. 40, gave considerably better control than B. L. 155 BX straight through (Plot 4) both on a 14 day schedule. Plot 1 also gave slightly better control than Plots 2 and 3, which received a lighter application (Table II) at more frequent intervals. The standard lead arsenate schedule gave the best control. The size of the fruit again was normal for the season in all plots, but the finish of the fruit from the plots which had received sulfur sprays was inferior be­ cause of residue and injury resulting from a combination of sulfur and heat, not necessarily at the time of the ap­ plication of sulfur. The plot receiving the B. L. 155 BX and summer oil had the best finish when packed, ^he lead arsenate plot had a heavy residue, with a trace of spotting in the color, due to the accumulation of the spray residue in drops. When picked the fruit was in excellent condition, but after washing it did not compare favorably with the other plots because of slight bruises. Relative Control. McIntosh. The McIntosh trees were very large and had produced three heavy crops In succession, thus developing the heaviest population of codling moths in the orchard. They were not pruned In anticipation of a light set in 1934, and a light set occurred, making spraying difficult. Precautions were taken to obtain the best possible coverage when spraying this variety, but the control was poor. -30Yields were sufficient to give significant figures, and the opportunity to study the materials under the most dif­ ficult conditions gave interesting results. The nicotine combinations gave decisively better control than the lead arsenate schedule, particularly Plot 3 . ent for several weeks before harvest. This was appar­ The lead arsenate plot showed a significant increase in the percentage of shallow entries as compared with the bentonite-nicotine combinations. This was apparently due to reduction in the codling moth population before the larvae attempted to enter the apples, for the total injuries, deep and shallow entries combined, may be considered the best in­ dex of the population or potential. Such a significant reduction in the number of total entries can only be due to effective ovicidal action in Plots 3 and 4, reducing the potential population. Relative Control. Jonathan. The Jonathans, harvested five weeks later, were located beside the McTntosh, and observa­ tions indicated that they shared the heavier moth popula­ tion incident to the conditions described. They were not pruned, in anticipation of a light set of fruit, but the count trees produced a normal crop. The data show a great­ er percentage of injury for this variety and resemble the results from the McTntosh in the relative control obtained by the different schedules. Again the lead arsenate sched­ ule was surpassed in percentage of clean apples by Plots 3 and 4, receiving 5 pounds of B. L. 155 BX (plus summer oil in No. 3). Plot 2 gave slightly more clean apples than the lead schedule, receiving a frequent application of three -31pounds of B, L. 155* Plot No. 1 dropped from second place to fifth, receiving B. L. 155 at 14-day intervals. Plot 6 , receiving no second brood applications, gave very poor control. Analysis of the proportion of shallow and deep entries in each treatment show that the lead arsenate schedule per­ mitted the development of more shallow entries but less deep entries than any of the bentonite-nicotine combinations. Five times as many shallow entries as deep entries were scored against the lead arsenate schedule, while in the bentonite-nicotine schedules the proportion was nearly equal. The shallow entries in the plot treated with lead arsenate were for the most part very small, a condition part­ ly resulting from the excellent coverage maintained in the absence of rains. The reduction in percentage of shallow entries in the case of the bentonite-nicotine combinations might well be correlated with a reduction in the moth popula­ tion in these plots rather than a reduction of larval popula­ tion, for the higher percentage of deep entries indicates poorer larval control than in the lead arsenate plots. Discussion of Relative Control Considering first the lead arsenate schedule, it is evi­ dent that while less deep entries usually resulted from this treatment than any other, the percentage of shallow entries materially reduced the percentage of clean apples, placing this schedule third in Jonathan and fourth in McIntosh. Plot No. 1 gave good control while &olofog and B. L. 40 were used, the control decreasing from 3.38% total injury to -3231.08# as the season advanced, with the use of B. L. 155 at 14-day intervals, shallow and deep entries at all times "being nearly equal. Plot No. 2 gave very good control, 1.80# total injury with a weekly application of B. L. 155 during the first brood, and almost as good during the early part of the second brood, when one-half per cent oil-nicotine was used, followed by three pounds B. L. 155 at 7-day intervals, but the latter part of the season showed a considerable de­ crease in control, (23.09# injury on Jonathan), indicating that the concentration should have been slightly greater* Plot No. 3 gave the best sustained control, receiving only three pounds B. L. 155 BX, with one per cent summer oil in the peak, for the first brood, and three pounds B. L. 155 BX with one-half per cent oil in the second brood. The early control was excellent, only 2.43# total injury on Yellow Transparents, and the control during the later part of the season was proportionately even better, only 16.17# total injury. The advantage may have been in the addition of the oil, although that concentration (J-#) is considered insufficient for control as an ovicide. Again, it may be due to the 1 0 -day interval used in this schedule during the second brood, the oil helping to retain the coverage, and perhaps thus affecting the insecticidal ef­ ficiency of the B. L. 155 BX. Plot No. 4 gave the poorest control on Wealthys, yet maintained nearly as good control on Jonathans, holding its position in relation to Plot No. 3. This plot receiv­ -33ed B. L. 155 BX at 14-day intervals for the second brood, giving five per cent less clean Jonathans than Wealthys, while Plot No. 1 received the same schedule of B. L. 155 and gave twenty-three per cent less clean Jonathans than Wealthys. This indicates an additional insecticidal ef­ ficiency for the B. L. 155 BX, and may explain the show­ ing of Plot No. 3. Plot No. 6 shows a control during the first brood and extending into the second brood which might be expect­ ed from such a heavy schedule during a dry season, but on varieties which ripened late the control was poor. This may be attributed to the growth of the apple and the weathering of the materials with a consequent reduc­ tion of coverage. For convenience in comparing the season relation of the various treatments, charts have been prepared which compare the percentage of clean apples in each variety for each treatment with the lead arsenate schedule. These are presented in Figure II. Lqflfi arpsnatf! eaci a r s e n a t e Yellow Trans Wealthy Jonathon PERCENTAGE OF CODLING MOTH INJURY - 1934 Figure II McIntosh -34SUMMARY The results may be summarized as follows: 1 . All schedules gave excellent control of the first brood of codling moth, thus effectively protecting summer varieties of apples. 2. Schedules including sulfur during the first brood caused injury to fruit and foliage. 3. Oil (with nicotine) applications caused injury when following sulfur. 4. Bentonite combinations gave control of codling moth, the B. L. 155 BX combinations slightly surpassing B. L. 155. 5. B. L. 155 BX combinations sustained control throughout the season, although not as effici­ ent at first. 6 . 7. 8 . Arsenate of lead schedules gave the best con­ trol of deep entries. Schedules confined to the first brood do not give sufficient control on fall varieties. Respite the alarming appearance of trees in­ jured by sulfur sprays, arsenate of lead caus­ ed more leaf fall. -35EXPERIMENTS IN 1955 Changes in Procedure. In 1935 all materials were applied on a 1 0 -day schedule of cover sprays, and, with one excep­ tion, no changes in materials were made during the season. This permitted exact comparison of materials alone, omitt­ ing variables of schedules and changes in materials during the season such as occurred in 1934. Furthermore by obtain­ ing complete control of the orchard, by lease, opportunity to study possible injury was afforded without jeopardizing satisfactory relations with the owner. This, of course, permitted inclusion of new and relatively untried materials. Varietal differences, responsible for large variations on data obtained in 1934, were controlled by acquiring a very uniform bloc]£ of trees, large enough to permit replica­ tion of plots and of such a regular bearing habit that all trees could be used as count trees. Varietal differences were tested in another block, from which data were obtained to compare, without obscuring, the data on relative control of the different schedules obtained on the uniform block. Other advantages afforded by the 1935 program were ef­ fective, reliable equipment, opportunity for unlimited study of crop during harvest, proximity to laboratory and other Experiment Station facilities, etc., all of which contribute to an effective research program. Changes in materials were occasioned by the inability of processed bentonite-nicotine sulfate compounds to withstand normal rainfall in eastern states in 1934. Driggers and Pepper -36(12) found that under New Jersey conditions the retention of nicotine by factory processed bentonite and nicotine sulfate compounds was much less than when the same ingredi­ ents were mixed at the time of application. The physical properties of the bentonite were apparently affected, and the control was poorest in the case of the B. L. 1 5 5 that was used with success in the Michigan experiments in 1934. Therefore, the !,155tT series in 1935 are modifications of those used in 1934, some of the formulae having been chang­ ed to increase adhesive or retentive properties. In addition, the Nico-Zin series was introduced, a soluble and non-volatile material to be used alone or with oil. The use of oils in combination with nicotine insecti­ cides was necessitated by the development of a new type of fTsoluble oilTf by Knight and Cleveland (28) and Cleveland (3). This material was tested by them in 1933 and 1934 and indicated certain advantages which necessitated its inclusion in the 1935 tests. The experiments in 1935 were confined to schedules comparing soluble and non-volatile nicotine combinations, (Nico-Zin series), soluble and volatile nicotine combina­ tions, (oil-nicotine series,) and Insoluble and non-vola­ tile nicotine combinations, (B. L. 155 series), with the standard arsenate of lead schedule as recommended by the Experiment Station of Michigan State College, both in control of the codling moth and in effect on the fruit and foliage of the tree. Each series included tests of combinations of the nicotine insecticide with one or more -37- summer oils in varying proportions. The schedule of cover sprays, Table VII, indicates the materials used and the amounts of each. Experimental Conditions. The orchard included about eight acres, which were divided into two types. The old orchard, Figure III, with 160 trees about 30 years old, included Baldwin, Spy and Ben Davis varieties, with a few Wealthys and scattered trees of other varieties of no importance. The orchard was planted too close, and had been overprimed at some time, causing many watersprouts. Subsequent neglect had permitted San Jose scale to build up, and the trees contained much dead wood. However, there were few trees gone, facilitating the arrangement of plots, and the condi­ tion of the trees afforded an opportunity to test materials under unfavorable spraying conditions. The dead limbs were removed, the watersprouts were thinned out, and the trees were cut back to permit the sprayer to pass between the rows, but no attempt was made to prune for easier spraying. to to_(L> to (L 0) (0 to ' to to) to (L CL CL PL to ' 0) to ( ) to CL (s) V0* to CP to to C L to "^ CL CL to to /'to ...to^P___ «-L LL c ) to (0 C) to to _to n to to to to 0 to to Cl T O a P a to to ■ cl c c Figure III. p to toto'L_- '■V -/ to -38Figure III illustrates the manner in which 13 plots were located in this area, each including a row of twelve trees across the main varieties, Baldwin, Spy and Ben Davis. Only the trees which hore a crop worthy of con­ sideration as a count tree were indicated on the map, so the omissions do not always indicate the lack of a tree* The young orchard, Figure IV, adjoined the old orchard on the west side and contained 112 McIntosh trees, about fourteen years old, planted at forty—foot intervals. In ad­ dition, one row west of the McIntosh included a few Yellow Transparent and Jonathan trees. k' GznziHn .q X T tct t e t d z d (7 O rQ - - U - U CT o fQ Z D E D CEO Q — f U ..U -.D O CTT~) CTT ^ ^ ' D Q -O d a~m n d CT 0 * 0 COZED 03 »CE () X) ( ) DX) (TUT) $ o ( )X) (T~rrec) 3T $ , ; I) c C ) Q>0 a_c).sic) d Figure IF. Q n o O O O ( )y»o cttt u e d o O QU2WD D () o D CT Q t e Q QZDED CT" 0 ^ 0 -39The McIntosh block was exceptionally uniform in size and vigor, and had been so cultivated that the trees were not suffering from lack of nutrition, though their growth was less than that of many young orchards. Their uniformi­ ty permitted the use of a replicated plot arrangement as shown in Figure IV, namely three replications of three tree plots. There were trees enough to accomodate 12 schedules in this manner, all trees being considered as count trees. trees. Omissions in Figure IV represent missing Plot No. 13 consisted of the Yellow Transparent row mentioned previously. No pruning was required, and spray­ ing conditions were optimum, so far as the trees were con­ cerned. Ammonium sulfate was applied at the rate 5# per tree In the old orchard and at the rate of 2j# per tree in the young orchard, in the delayed dormant period, ^his result­ ed in vigorous growth of the young trees and a sufficient growth of the old trees without production of watersprouts in either case. This rather light application of fertilizer was indicated to guard against stimulation of growth to such a point that spray injury studies would be impossible. Applications were made with a Bean Sprayer, developing 350-425 lbs. pressure. An eight nozzle broom gun was usually used in the young trees, spraying from the tank, while a Bean single nozzle gun was used in the old block, except when weath­ er conditions permitted using the broom only for the applica­ tion on one side, and the single nozzle gun for the other. In the old block the single gun was also used for spraying the under side of the trees from the ground, ^ae^ application -40was complete, and only twice were the applications in­ terrupted by rain. Spray applications during the pre-blossom, calyx, and first cover period were uniform for the whole orchard, and were modified to conform with weather conditions and other requirements as indicated in Table Vi. -41- TABLE VI SPRAY SCHEDULE - MASON, MICHIGAN 1935 Date Trees Apr. 2 0 ,2 2 McIntosh Material Rainfall since previous spray Bordo 4-4-50,Kleenup Z%9 B. L. 40, 1 pt. 22 All old trees Bordo 4-4-50,Kleenup 3% except Spies B. L. 40, 1 pt. 27 Spies 0.00 Bordo 4-4-50,Kleenup 3$, B. L. 40, 1 pt. FIRST APPLICATION Apr. 30 All W. All E. but Spies--Lime sulfur Gals. side) but Spies--Lead arsenate 3 pounds. side) .71 SECOND APPLICATION May 4 Both sides all trees Lime sulfur 2\ Gals. Lead arsenate 3 pounds. 1.24 THIRD APPLICATION May 6,7 Both sides all trees Lime sulfur 2 § Gals. Lead arsenate 3 pounds. .31 FOURTH APPLICATION May 1 0 11 West side) all trees) East side) all trees) Lime sulfur 2\ Gals. Lead arsenate 3 pounds. .21 FIFTH APPLICATION May 14 E. side) all trees) NW & NE side Mcl 1s) Lime sulfur 2\ Gals. Lead arsenate 3 pounds. N & S sides) Lime sulfur 2 j Gals. all trees) Lead arsenate 3 pounds. S . side M c l *s] STYTH APPLICATION .32 -42- TABLE VI SPRAY SCHEDULE - MASON, MICHIGAN 1935 Continued I— ..... Date — - Trees — - Material - — ■— ----------- -— Lime sulfur 2i Gals. Lead arsenate 3 pounds. 28 E & N side M c l fs Lime sulfur 2§ Gals. Lead arsenate 3 pounds. 29 W side M e l ’s Light application: Lime sulfur 2j Gals. Lead arsenate 3 pounds. 29 All but Spies in old block Lime sulfur 2 j Gals. Lead arsenate 3 pounds. 31 Spies Lime sulfur 2j Gals. 1.37 Lead arsenate 3 pounds. CO to • S & W side M c l 1s CALYX 8 N & S side old trees 1.09 Lime sulfur 2-J Gals. Lead arsenate 3 pounds. E side of M c l fs Lime sulfur 2j Gals. Lead arsenate 3 pounds. FIRST COVER - Rainfall since previous spray flay 27 June 7 --------- The first application, of three per cent dormant oil, Bordeaux 4-4-50 and B. L. 40, 1:800, was applied in the delayed dormant period for control of scale, scab, and aphis. Five subsequent pre-blossom sprays were re­ quired for control of scab and chewing insects, consist­ ing of lime sulfur, pounds. gallons, lead arsenate, three During the pre-blossom period, persistent rains required additional fungicidal protection, as shown by the amount of rainfall between applications. VI, column 4.) (See Table The calyx applications were made May 27- 31, and the first cover on June 7-8, with the same ma­ terials as used in the pre-blossom sprays. This complet­ ed the schedule for control of scab and curculio, and no primary scab infection developed. Experimental Materials and Methods. The application made on June 16-17, was the first of the series of experimental schedules, and subsequently all plots were sprayed with the materials outlined in Table VII, at ten-day intervals, as indicated in Table VIII. The only exception was Plot 8 , the base check or standard of comparison, lead arsenate and lime, which was sprayed at 14-day intervals, as recommended by the Department of Entomology. The last application was made on the 26th of August, and completed the eighth of the series of nicotine sprays and the sixth of the lead arsenate series. Comparable materials such as Nico-Zin, the oil-nicotines, or the 1 5 5 rs, were sprayed on the same day, to assure uniform weathering in event of interruption by rain. Three hundred gallons were found to be sufficient to cover twelve old trees and nine young trees, less being required in a few plots where trees were missing. -44TABLE VII CODLING MOTH PROJECT MASON, MICHIGAN 1935 Schedule of Cover Sprays (1 0 -day interval.) 1. Nico-Zin (20$), 2 #;*Verdol, 1 gal. 2. Nico-Zin (20$), 2#; Verdol, \ gal. 3. Nico-Zin (20$), 2#; Orthol-K, § gal. 4. Nico-Zin (20$), 2#;Superla, \ gal. 5. Nico-Zin (20$), 2 #. 6 . 7. Base check, college schedule: lead arsenate, 3#; lime, 4#. B. L. 40, f pt.; Verdol, J gal. 8. B. L. 40, f pt. Orthol-K, f gal. B. L. 40, f pt. Superla, f gal. B. L. 155 A, 5# * Orthol-K, 1 gal. 11. B. L. 155 B, 5# 12. B. L. 155 C, 5#; * Orthol-K, 13. Tank mix: 9. 10 . B. L.40, 1 gal. f pt.;Bentonite, 4#. (first brood.) B. L. 40, f pt.; Orthol-K, f gal. (second brood.) * - Oil included in application at time of peak emergence only. -45TABLE VIII COVER SPRAYS 1935 1 2 3 4 5 1. Junel9x X X X X 27x x (oil) 28 X X X 20 2* July 1 3* x X X . 8 9 10 11 12 13 X X X X X X X X X X X X x(oil) X X X X Rainf a! since previo' spray 1.81 1.98 x( oil) X X .57 X X X X X X X X X X .29 X X X X X X X X X X 1.81 X X X X X X X X X X X X X X 1.37 X X X X X X 12 8 7 X 8x (oil) 9 15 X 4. 17x 18 X 5* 26x 27 29 6 . Aug. 6 X 7x 7, 6 16 17x 19 26 27x X X X X X X .10 X .95 X X X X X X X X X X X X 2.68 Sept. 30 8 Nicotine covers 6 Lead Arsenate covers -46Results Nicotine Deposition. Analysis of the nicotine present on the foliage during the period of application was made by the method first used by Leonard (29) and later in New Jersey by Driggers and Pepper (1 1 , 1 2 ). Samples were collected before and after the fifth nicotine spray on July 26 and 27, and before and after the seventh nicotine spray on August 16 and 19, and before and after the eighth nicotine spray on August 26 and 27. One hundred leaves per plot were picked before the spray was applied, and again after spraying. Discs were cut from these leaves with a punch having a diameter of one and a quarter inches and these samples were analyzed to determine the amount of nicotine in mgs., per sq. cm. x 10-3 . analysis are included in Table X. The figures of the -47TAELE X MASON, MICHIGAN CODLING MOTH PROJECT 1955 Analyses of apple foliage (McIntosh) for Nicotine ?lot No* 5th Nicotine Spray Before After 7th Nicotine Spray 8 th Before Before After Nicotine Spray After 1 1.11 2.42 1.45 1.77 1.32 3.25 2 1.29 2.79 1.57 2.26 1.05 2.52 3 1.38 3.53 1.81 2.25 1.27 5.31 4 1.59 3.03 1.87 3.15 1.10 5.25 5 0.57 1.72 1.51 1.36 0.20 1.45 7 0.44 1.28 1.02 1.05 0.16 1.65 8 0.57 1.16 1.03 1.50 0.00 1.02 9 0.87 1.65 3.08 1.46 0.37 1.50 10 1.08 2.40 1.42 2.81 2.23 1.79 11 0.40 2.14 1.42 2.06 0.74 0.95 12 0.59 2.19 1.49 2.52 1.42 2.06 13 2.94 3.91 5.85 4.10 6.15 Amounts shown are in mgs. per sq. cm. x 1 0 - 3 -48The Nico-Zin series with oil added retained for 1 0 days approximately three times as much nicotine as Plot 5, receiving Nico-Zin alone. The Nico-Zin oil plots, however, have less than twice as much nicotine immediately after the spray application has been made. In this respect the Nico- Zin oil combination seems very effective. The amount of nicotine remaining at the end of the 10 day interval between sprays is approximately equal on the plot receiving Nico-Zin alone and on the oil-nicotine plots, according to the information in Table X, The B. L. 155 series, Plots 1 0 , 1 1 and 1 2 , indicate a varying amount of nicotine retained during the period between sprays. The amount is relatively low in the case of Plots 1 1 and 1 2 , and relatively high in the case of Plot 10. The amount present immediately after spraying is approximately the same in all three plots, so the retention in Plot 1 0 must be more efficient. The Effect on Foliage. The effect of the insecticidal ma­ terials on the tree, as manifested by the foliage, was again studied in 1935. The injury to the leaves on the non-bear­ ing spurs, which are present and exposed to the spray during the entire season, was measured by determining the average number of leaves per spur early in the season, then comparing this number with the averages taken at intervals during the spraying. The uniformity of the McIntosh block permitted this type of measurement, while variation in vigor between trees in the old block prevented its application there. ly 4-.VJQ data ^ere obtained from nn 4.fora, ^ut According­ -49and consequently less susceptible block of trees. The average number of leaves per spur was determined by count­ ing 300 spurs per plot and computing the average. Three counts were taken at monthly intervals on the McIntosh block, and the percentage of leaves lost during each in­ terval computed, as shown in Table IX. Table IX, in general, shows no loss of importance, with the exception of Plots 4 and 9, both of which receiv­ ed Superla, at one-half and one-fourth per cent strength respectively. This is in marked contrast to the differenc­ es shown by the same index in 1934, but conditions were less favorable for leaf loss this year because of the regu­ lar rainfall. Also, the method best demonstrates true de­ foliating Injury such as lead arsenate without a corrective, or oil after sulfur injury. Injury from oil only was notic­ ed this season as a marginal burning, resulting eventually in a ragged, frayed leaf which adhered normally until late in the season, when the loss occurred which is indicated in the last count, Table IX, column 5. Observations made during the summer on the McIntosh block indicated conclusively that the Nico-Zin series, in­ cluding the plot of Nico-Zin alone, five pounds, caused a yellowish type of foliage, most noticeable by contrast with the unsprayed trees, or the B. L. 155 plots. The B. L. 155 series had the best general appearance of any of the spray treatments. The oil-nicotine plots naturally showed a dark­ er green foliage, as is characteristic, but the inclusion of oil in the Nico-Zin plots did not mask the yellowish col­ or at all. As the leaf counts indicated, the lead arsenate -50TABLE IX LEAF COUNTS - MCINTOSH - MASON, MICH* 1935 July 1-5 Leaves per twig July 30-Aug. 1 Leaves per-% loss twig Sept* 1 Leaves per~$ loss twig 1 6.09 5.83 4.25 4.33 28.90 2 6*11 5.89 3.60 4.34 28.97 3 6*80 5.91 4.68 4.50 27.42 4 6.16 5.67 7.95 3.90 36.69 5 6.18 5.92 3.27 4.07 33.50 6 6.87 5.75 9.25 4.25 32.22 7 6.16 5.88 4.55 4.07 33.93 8 6.85 5.97 4.48 4.16 33.44 9 5.98 5.79 .17 3.63 39.30 10 6.11 5.89 3.60 4.37 28.48 11 6.04 5.80 3.97 4.20 30.46 12 6.81 5.89 5.15 4.26 31.40 13 5.70 5.13 10.00 4.09 28.25 -51plot in the McIntosh did not lose any leaves. The yellowing of the foliage on the Nico-Zin series was most evident in the McIntosh block, yet as has been stated, no leaf fall occurred. In the old orchard no in­ jury from this material appeared until fairly late in the season when the Nico-Zin series and the oil-nicotine series experienced a considerable drop of yellowed leaves during the middle of August. The leaf fall at this time was suf­ ficient to equal that which had occurred on the lead ar­ senate plot in the old block previously, though no particu­ lar leaf fall was occurring then on the lead plot. The leaf fall was most noticeable on Spies, and of course, oc­ curred first on limbs which had been weakened from scale or shading. The oil-nicotine plots in the old block showed darker foliage that was not in as desirable condition as the foli­ age on the B. L. 155 series, but showed no leaf loss until the early part of September, after which the leaf fall was so rapid as to be very noticeable by the first of October, both on the spurs and on the new growth. The plots receiv­ ing the B. L. 155 A, B, or C, with or without oil, had by far the best color and condition of foliage through the entire season, and the leaves persisted in healthy condi­ tion longer than those on any other treatment. In contrast to the lead arsenate plot in the McIntosh block, which has been described as free from any leaf loss, the same treatment in the old orchard gave a considerable leaf drop, which began about the latter part of July and continued through the season, though at no time were any -52great number of leaves falling. At the time of Ben Davis harvest, late in Octo­ ber, the trees of this variety which had received NicoZin showed ragged bronzed foliage with considerable leaf loss, while the trees that received lead arsenate appear­ ed healthier due primarily to the green color of the leaves which persisted. The Effect on Fruit. Color. Observations made prior to the time of harvest of the McIntosh indicated the possibili­ ty of a color deficiency in the series of plots receiving Nico-Zin, but the effect was masked by considerable varia­ tions from tree to tree which might have been attributed to variation in strain, making it very difficult to draw definite conclusions as to the effect of these materials on color. Fruit from the oil-nicotine plots In general showed a poorer quality of color, almost a brick red, than the trees sprayed with lead arsenate or B. L. 155 A, B, or C. At the time the apples were ready to be harvested, a few warm nights accented the variation In color to such an extent that a measurement of the variation was attempt­ ed. Random samples of approximately one hundred apples were taken, including each tree in each plot. Each sample was then separated into Michigan "Fancy," Michigan TTA , T! and Michigan nB n grade on the basis of color alone. results are indicated in Table XI. The -55TABLE XI Plot No. Fancy Number Michig an A B Percent Michigan Fancy A B 1 0 57 31 0 65 35 2 6 35 45 7 41 52 3 0 30 62 0 33 66 4 2 69 24 2 73 25 5 6 54 23 7 65 28 6 26 32 27 30 38 32 7 19 27 41 22 31 47 8 25 37 18 31 46 23 9 19 33 32 23 39 38 10 3 37 51 3 41 56 11 0 48 42 0 53 47 12 3 77 10 3 86 11 Unsprayed23 20 30 32 27 41 -54Color is a requirement in Michigan "A” and Michigan "Fancy," while Michigan "B" requires no color. Fifteen percent of normal color is required on McIntosh for Michi­ gan "A," and this grade is about the same as TJ. S. No. 1. Fifty percent of color is required for Michigan "Fancy" (31). In consideration of Table X I , a remarkable correla­ tion is evident between percentage of Michigan "Fancy" and the various series of materials. According to these data the effect of the Nico-Zin and B. L. 155 series of treatments was to eliminate the highly colored apples which would normally be included in Michigan "Fancy," most of which are dropped to Michigan "A". Plot 6 , the lead arsenate plot, shows a small percentage of Michigan "B" and a percentage of Michigan "Fancy" very closely comparing to the results of the unsprayed trees. The oil-nicotine series apparently gave normal color, though no increase in Michigan "Fancy" can be attributed to the oil-nicotine treatments. The B. L. 155 series, while hav­ ing as desirable type of color as any of the treatments, produced a very low percentage of Michigan "Fancy" apples. It must be pointed out, however, that the percentage of Michigan "A" apples in this series is relatively higher than in any other, particularly in Plot 12. Michigan "A" grade corresponds very closely with the U. S. No. 1 Grade, as far as color requirements are concerned. Therefore, it would seem that while the B. L. 155 series were deficient in Michigan "Fancy" apples, the increase in the number of -55Mi chigan "A" would justify calling the color reactions on these treatments desirable. Some deficiency in color may have resulted from the greater percentage of healthy leaves remaining on the trees in the B. L. 155 plots at harvest. The Effect on Fruit. Dropping. In conjunction with the observations on color of the McIntosh, a considerable drop of fruit was noticed on several plots. To determine the significance of this effect of the various schedules, the dropped apples were recorded in Table XII. TABLE XII PERCENTAGE OF DROP MCINTOSH, MASON, MICHIGAN 1935 Plot No. 1 Mean % Replication 2 3 3.6 14.6 1 24.5 16.7 2 22.4 —1™ 23.6 19.3 3 23.6 19.1 23.8 20.5 4 58.2 47.9 48.3 53.4 5 15.0 18.2 11.3 14.4 6 38.5 12.2 20.8 26.1 7 36.9 34.5 10.5 26.3 8 50.5 35.3 61.8 50.9 9 62.9 36.8 72.7 57.7 10 20.6 4.1 17.3 13.1 11 11.2 10.7 15.2 12.3 12 16.5 26.1 14.5 17.8 26.1 Unsprayed Average 27.1 -57The average drop for the variety as a whole was 27.1$. The only plots showing decided increase when com­ pared with unsprayed trees were No. 4 and No. 9 , receiv­ ing Superla in one-half and three-fourths per cent concen­ trations in all cover sprays; and No. 8 , receiving threefourths per cent Orthol-K. However, all schedules includ­ ing oil in all cover sprays increased dropping. Nico-Zin used alone (Plot No. 5) or with one per cent oil in three sprays reduced dropping, as did the "155” series on Plots 10, 11 and 12. The additional dropping in Plots No. 4 and No. 9 may he attributed to the increased oil concentration at equal dilution, for the !1soluble” type contains 9 5 $ actual oil, while the others, of the "mayonnaise” type may only contain 65-85$ actual oil (3)♦ Furthermore the soluble type was developed for use in combination with lead arsenate in which case the insoluble suspensoid is coated with oil, stabilizing the emulsion. In the absence of such a stabilizing action, when used with soluble nicotine sul­ fate or Nico-Zin in these experiments, difficulty is always experienced in obtaining complete emulsification. The Effect on Photosynthesis. Photosynthetic effects of the different materials were advanced as a cause of the vari­ ations in color, and in dropping. Accordingly random samples of one hundred leaves were taken from each of Plots No. 2, 3, 4 , 5, 6 , 7, 8 , 9 and the unsprayed trees, for analysis of carbohydrates present. -58'Samples were taken early in the morning of September 17th, and again Just before dark. A circular disc was cut from the center of each, in the same manner as for nicotine analysis, to assure uniform size of samples. These samples were analyzed for content of glucose, sucrose, starches and total carbohydrates, and the data are presented in Table XIII as percentages. Considerable variations are indicated between treat­ ments, but the differences are in many instances too small to show variations between plots. Therefore the data pre­ sented in Tables XI, XII, and XIII have been collected and arranged to best indicate variations, in Table XIV. Relative Effect. All Types. In Table XIV the Plots receiv­ ing Nico-Zin with one-half per cent oil have been consider­ ed in the first column, and those receiving B. three-fourths per cent oil in column two. l . 40 with No consideration is given the variations due to use of different oils, for all three types of oils were used in each group. These data are to be compared with the lead arsenate standard, the un­ sprayed trees, and the plot receiving Nico-Zin alone. Data include the percentage of fruit remaining on the trees at harvest, which was highest in the Nico-Zin plot, and lowest in the plots receiving the heaviest oil concentration. Oil in both cases increased dropping, lead arsenate did not af­ fect it, and Nico-Zin retarded it. The percentage of fruit having Michigan "A” color (over 15$) was increased slightly by oil-nicotine, considerably by Nico-Zin alone, but reduced by Nico-Zin and oil combined. The total carbohydrates are in close relationship to -59TABLE XIII MASON, MICHIGAN CODLING MOTH PROJECT 1935 SUMMARY OF DATA ON CARBOHYDRATES Percentage of Starches Sucrose Total Treatment Time Unsprayed A.M. P.M. 7.73 7.95 8.98 11.39 12.75 14.87 29.62 34.21 Number 2 A.M. P.M. 6.58 7.14 9.33 11.02 15.29 13.93 31.19 32.09 A.M. P.M. 7.54 6.68 9.52 11.28 16.04 13.99 32.84 31.96 Number 4 A.M. P.M. 7.82 7.03 10.49 11.69 14.38 13.20 32.70 31.93 Number 5 A.M. P.M. 7.55 8.72 9.64 11.56 13.64 14.66 30.78 35.95 Number 6 A.M. P.M. 8.23 8.67 11.01 11.73 11.59 16.13 32.86 36.59 A.M. P.M. 8.32 8.24 10.63 14.03 15.06 34.35 33.95 Number 8 A.M. P.M. 7.82 8.71 10.23 10.14 12.35 16.22 30.51 35.08 Number 9 A.M. P.M. 9.13 8.48 11.17 10.67 12.85 13.73 33.16 32.89 Number 3 Number 7 Glucose 12.00 -60- TABLE XIV MCINTOSH BLOCK - MASON, MICHIGAN September, 1955 Plots Numbered: M a t TIs. used in Cover Sprays: 2,3,4 7,8,9 Nico-Zin oil B.L. 40 oil 5 U 6 Lead ^rs. No Cover Spray Lime Nico-Zin Alone Percent of Picked Fruit: 69.3 55.0 73.9 73.9 85.6 Percent of U. S. # 1 Color: 52 64 68 59 72 Increase % Total Carbohydrates from A.M.-P.M.* Increase % Total in Glucose-Sucros<& from A.M.-P.M.* -.75 1.30 3.73 4.59 5.17 .59 -.28 .48 1.32 1.55 * Samples taken September 17th. -61color, with the Nico-Zin-oil the lowest, and only the Nico-Zin above the unsprayed* The figures for glucose and sucrose have been com­ bined, and are perhaps the most important factor present­ ed, for in analysis of fruit their presence is correlat­ ed with quality (2 ), and pigmentation is also correlated with their presence (22)* Again the addition of oil to Nico-Zin affected this material, lowering it from first place to last. The proportionate reductionin the oil- nicotine and lead arsenate plots is large because of the high starch content included in the total carbohydrate analysis of the leaves from these plots (Table XIII). These data indicate a definite reduction in photo­ synthesis where oils were used, and additional reduction in color when Nico-Zin was combined with oil. An observation worthy of mention in this respect is that the plot receiving Nico-Zin alone, in the old block, contained a Spy tree and a Baldwin that bore the most highly colored fruit of these varieties. Additional In.lurv to Fruit. Injury to the calyx end of the apple was also observed, first as a green area in the calyx depression, later russeting on the same area. This injury occurred on all McIntosh plots receiving oil in all cover sprays to a considerable extent, and occasionally on Plot 1, which had 1% oil in three applications, ^o variation in the manifestation of this injury occurred except in degree, and was probably related to the actual oil content of the emul­ sion used, for Superla, with the greatest concentration of oil, caused the earliest development of the calyx injury. The injury characteristic of Plots No. 4 and ^o. 9, re- -62ceiving Superla oil in all cover sprays, is shown in Figure V. Figure V. Superla summer oil on McIntosh. -63The injury characteristic of Plots No. 3 and No. 7 caused by the inclusion of Orthol-K oil in all cover sprays is indicated in Figure VI. Figure VI. Orthol-K summer oil on McIntosh -64The injury resulting from the inclusion of Verdol oil in Plots 1, 2, and 7 is shown in Figure VII. Figure VII. Verdol summer oil on McIntosh. -65This type of injury was manifest on the Spies in the old block in Plot 9 , which received three-fourths per cent Superla, as a black specking of the calyx and the face of the apple exposed to the heaviest spray. The injury appeared about the first week in September and by the time of harvest most apples had outgrown the injury. Figure V I I I illustrates the black specking of the surface exposed to the spray. Ficrure VIIt Superla summer oil on Northern Spy. -66- Another type of oil injury was observed, but only occasionally, on Spies. This was enlarged and ruptured lenticils, as was mentioned by Cleveland (3). This is shown in Figure IX. Figure IX. Superla summer oil on Northern Spy. A few examples of a peculiar type of injury on the plot sprayed with lead arsenate were observed. This injury occurs after the fruit starts to ripen, and is caused by the accumulation of arsenical residues in the calyx end of the apple with resultant formation of soluble arsenic, causing a sunken, black area in the calyx depression (13). X. This is illustrated by Figure The solid color of the fruit indicates the maturity of the apples injured in this manner. Figure X. Lead Arsenate on McIntosh - 68 - No uniform variation in color was observed in the bid orchard, for while some variation was apparent be­ tween plots, it was not greater than the variation be­ tween trees in the same plot, because of the condition of the trees under experiment. However, the condition and finish of the fruit in the 155 plots was by far the best of any series. Codling Moth Control Population Conditions. Observations on the codling moth population during the summer were as detailed as possible for the available data on this important factor were lim­ ited. As has been mentioned, inefficient spraying during bearing years, and neglect during non-bearing periods, had prevailed. The orchard had not borne the previous year, and no information was available about the condition of earlier crops. Examination of the trees indicated that there had been high populations present, but no great num­ ber of worms were found in the cocoons under the bark flakes, by casual inspection. In order to increase the population about 100 untreated corrugated paper bands containing larvae collected the pre­ vious season were distributed in the orchard. The number of larvae per band varied considerably, but was estimated to average about 1 0 0 . One band was placed in the center tree of each plot in the McIntosh block, and the rest were distributed in the old block, in trees which had blossomed fully. The bands were distributed about the first of June. On the 8 th of June, two pupae found on the trunk of one of the trees indicated that emergence had begun, at least -69of the original infestation. However, the prevailing cold, wet weather prevented any considerable emergence, and certainly any egg deposition. On June 29th approxi­ mately 1 0 0 0 moths obtained from an apple storage at Albion, Michigan were liberated in the old orchard, and about 1000 more were liberated in the McIntosh block on July 1 st. Liberations were made late in the day and the majority of the moths flew readily from the container to trees at some distance, apparently in excellent condition. Still another liberation was made in the McIntosh block on the 7th of July, of about 500 moths. The peak emergence of moths from the original orchard infestation and from the bands distributed was delayed by the cold weather until the 2 nd of July. On this date fa­ vorable conditions caused large numbers to emerge, although flight conditions were still unfavorable, for bait pot col­ lections during the following week were much lower than they should have been after such an emergence. The afternoon of July 2 nd was spent in examining various trees in the old or­ chard, and from six to twelve moths were commonly observed on each tree, emerging from the bands, the crotch of the limbs, or the base of the trunk. Some larvae had tunneled into the wood In injured areas, such as where limbs had broken off, and there had wintered, safe from predators. Obviously, the original infestation had been underestimat­ ed, and in addition, the emergence from the bands was ex­ cellent. However, the emergence was at least two weeks later than customary, and rather than being distributed over a period usually necessitating several sprays, it was -70concentrated during the period protected by the appli­ cation of July 6th. ^ome emergence occurred during the rest of the month, and continued until the peak second brood emergence was reported by the Experiment Station on the 29th of July at East Lansing. This emergence did not include individuals result­ ing from the peak flight of July 2nd, so the increase in the orchard population was relatively slight. During the four weeks following, the flight was below normal in the orchard, though a considerable flight was reported from points slightly south on the 18th to the 22nd of August. Some very young larvae were found during the week of 29th of August, but moth flight was retarded by temperatures of 65 degrees and below, for the next ten days. A flight reported in some sections of the State about the 15th of September vfas of no importance in the orchard. Summarizing the codling moth population in the or­ chard for the season, It may be considered that the emerg­ ence of a satisfactory first brood population was delayed by unfavorable weather, and the flight interrupted, until the second brood represented only the first third of the generation. In other words, population build up during the summer was below normal. Relative Control, on McIntosh. Results of counts on all apples from the McIntosh block are outlined in Tables XV, XVI, XVII, XVIII, XIX, XX. Results are computed on the basis of deep entries or shallow entries, per 100 apples. - 71 - TABLE XV CODLING MOTH INJURY - MCINTOSH - MASON, MICHIGAN 1955 Plot No. No. Apples % Entries 1 2 3 % Entries ^Weighted Mean 1 8518 Deep Shallow .61 1.05 .96 1.38 1.81 .76 1.15 1.03 2 9927 Deep Shallow 1.10 .85 1.52 2.82 2.41 1.58 1.80 1.69 3 6988 Deep Shallow .99 1.10 .62 2.48 1.11 .90 1.03 1.08 4 11577 Peep Shallow .42 .52 1.94 1.01 1.82 1.03 1.26 .80 5 12423 Peep Shallow 5.75 2.18 7.08 6.82 2.21 3.82 4.83 3. 66 6 13429 Deep Shallow .88 2.51 4.55 14.46 .81 7.21 1.50 9.61 7 7236 Deep Shallow 1.35 1.93 2.40 1.97 1.54 4.26 1.74 2.82 8 9293 Peep Shallow 1.33 1.46 .26 1.64 1.70 2.56 1.76 1.95 9 8248 Deep Shallow 1.49 1.16 .26 1.33 .65 1.12 .78 1.20 10 11745 Deep Shallow 3.21 3.03 .20 1.05 .92 2.35 1.19 2.02 11 10745 Deep Shallow 4.18 3.99 4.04 4.07 4.43 2.43 4.22 3.52 12 11381 Peep Shallow 3.86 2.46 3.98 2.86 2.45 2.51 3.26 2.57 Unsprayed 4554 Peep Shallow 14.16 4.50 * 14.16 4.50 Weighted mean - calculated by dividing total wormy fruit by total fruit • -72In analyzing Table XV, certain gross characteristics appear. Several groups of plots show little variation in percentage of injury, either as deep or shallow injuries. In most cases this Is due to the small variations in effec­ tiveness between the toxicants in the different schedules. For instance, the striking example is that of the Nico-Zin series, in which the inclusion of oil, either one-half per cent in all covers, or one per cent in three peak applica­ tions, resulted in decrease of injury to a low but -uniform figure, regardless of the type of oil used. Conclusions can best be drawn by combining the data in another group­ ing, thus eliminating consideration of insignificant vari­ ations . Table XVI includes the same data, assembled as total injury. The data In Table XVI show increased variation between plots, particularly when the observed means of the comparable groups of plots of Nico-Zin-oil, oil-nicotine, and B. L. 1 5 5 fs are collected in respective means, then compared with the Nico-Zin alone or the lead arsenate standard. Statistical Significance of Differences in Control. The sta­ tistical treatment included in Table XVI is based on the analy­ sis of variance as described by Snedecor (34). It is included to establish the significance of the data presented. The general significance is obtained by comparison of the mean square of the variance between plots with that within plots, usually considered the experimental error. In this case the mean square between plots is 41.12 times as large as that within plots. This value (F) is influenced by the number of -73- TABLE XVI % TOTAL INJURY - MCINTOSH 1935 % E N T R I E S Plot 1 Replication £ 3 Obs. Mean Sums Squared degrees R reedom Mean Squares .92 1 1.66 2.34 2.59 2 1.95 4.34 3.99 3 2.09 3.10 2.01 4 .94 2.95 2.85 2.57 10.11 11. 5 7.93 13.90 6.03 9.29 33.74 2 16.87 6 5.43 16.97 8.02 10.14 73.52 2 36.66 7 3.28 4.37 5.80 8 2.79 1.90 4.26 9 2.65 1.59 1.75 3.15 16.03 8 2.00 10 6.24 1.25 3.27 11 8.17 8.11 6.86 12 6.32 6.84 4.96 5.78 41.42 8 5.18 Between Means 59.62 Within Groups 1.45 -74degrees of freedom, and the significant figure in this instance would he 5.27. This is expected to he exceeded in random sampling from a homogeneous population only once in a hundred trials. Obviously when F ^ 41.12 the chances are remote that differences in Table XVI are due to random sampling. The same relationship obtains in the mean squares as computed for each group of plots. In Table XVII the lead arsenate plot has been used as a standard and the relative control of the others indicated, with the significance of each. By these criteria it is evident that the Nico-Zin with oil and nicotine sulfate with oil resulted in significantly less codling moth injury, all forms, than the standard, lead arsenate. The chances of these differences being due to random sampling are less than 1:100. The B. L. 155 series gave less significantly better results, for the chances of the decrease in total injury of 4.36$ being due to random sampling are only little less than 5:100. The Nico-Zin (used alone) failed to give a signifi­ cant reduction in total injury. In this respect it should be pointed out that the NicoZin was most efficient when used with oil, for the chances that the reduction of 6.72$ injury when oil was included was due to random sampling are less than 1:100 (F - 18.33, signifi­ cant at 7.20). Control of Deep Entries. Separating the classes of in­ jury and consideration of deep entries separately results in rearrangement of some schedules in relative control. In - 75 - TABLE XVII RELATIVE CONTROL OF CODLING MOTH MEAN % OF INJURY - AND SIGNIFICANCE. Mean Square Lead Ars enat e 6 10,14 2 56.66 Nico-Zin 5 9.29 2 16.87 2.17 99.01 10-12 5.78 8 5.18 7.08 4.46 8.65 Nicotineoil 7-9 5.15 8 2.00 18.55 4.46 8.65 Nico-Zinoil 1-4 2.57 11 .92 59.84 5.98 7.20 ”155” 56.66 p X * Degrees Freedom Gi Obs. Mean rH Plots o o F ”Significant” 5:100 1:100 Material - 76 - Table XVIII the relative control of deep entries is pre­ sented* Statistical Significance of Differences in Control* Again the lead arsenate standard is separated, and all plots hav­ ing less than two per cent deep entries are collected in one group and compared with the standard, as are those with over two per cent deep entries, in a second group* Only Plot 5, receiving Nico-Zin alone, and Plots 11 and 12, re­ ceiving B„ L* 155 B and C respectively, are Included in the second category. This separation is justified by the fact that the variation within these groupings is very small in relation to that between them. F (within groups) is equal to 59.67/.94 or 65.48, while the significant figure is 5.27. The error in this grouping, then, is very small. The mean square of variance between the means of the groups is 59.67, while that within the groupings, the error, is .94. The value of F is 61.78, while the value required for significance (1:100) is 5.27. This entirely justifies the method of separation of the data. There is no significant difference between the control of deep entries achieved by the Nico-Zln-oil, oil-nicotine, and B. L. 155 A schedules, and that of the lead arsenate. The value of F in this instance is .57, and to be signifi­ cant should be at least 5.42. Neither is the decreased control by Nico-Zin, B. L- 155 B or B. L. 155 C (Plots 5, 11, and 12) significantly poorer, because of the small num­ ber of degrees of freedom in Plot 6. However, if plot 6, not significantly different than from plots 1-4 and 7-10, be combined with them, the F value is hardly affected, but the - 77 - TABLE XVIII RELATIVE CODLING MOTH CONTROL - MCINTOSH ^ D E E P E N T R I E S Plot 1 Replication 2 1 .61 .96 1.81 2 1.10 1.52 2.41 3 .99 .62 1 •11 4 .42 1.94 1.82 7 1.35 2.40 1.54 8 1.33 .26 1.70 9 1.49 .26 .63 10 3.21 .20 6 .88 5 Mean Squares Ohs. Mean Sum Squares .92 1.28 13.27 23 .58 2.51 .81 1.40 4.32 2 2.16 5.75 7.08 2.21 11 4.18 4.04 4.43 12 3.88 3.98 2.45 4.22 17.95 8 2.98 3 Degrees Freedom Between Means 59.67 Within Groups .94 — . . -------------- j. - 78 - greater degrees of freedom give significance. The signifi­ cant F figure under these latter conditions is 3.29, while the computed F is 5.14. The control in Plots 5, 11 and 12 is therefore significantly poorer than in Plots 1-4 and 6-10 . It is therefore evident that all treatments gave con­ trol of deep entries equal to that of the lead arsenate schedule, except Nico-Zin alone, B. L. 155 B and B. L. 155 C. It seems unnecessary to point out that the percent of fruit injured by shallow entries was an important factor in the production of clean fruit by the use of lead arsen­ ate. Relation of Nicotine Deposit to Control. Another factor which should be directly related to the degree of codling moth control achieved by various combinations of nicotine is the amount of nicotine deposited by each application on the leaves and fruit. Ihis information is available in Table X, in which is collected results of analyses of foli­ age before and after spraying. By subtracting the amount usually present before spraying from that present after the application a figure representing the average amount applied per plot per application is obtained. The similarity of these results within the different series of schedules has prompted the collection of the data for the various series and its expression in Table XIX as arithmetical means, and also as relative percentages. -79- TABLE XIX CODLING MOTH CONTROL AND NICOTINE DEPOSITION Material Nico-Zin \% Oil B. L. 155 A. B. C. Plot ^Nicotine Deposited Injuries per 100 Apples Mean % Decrease Mean % 1-4 1* 72 100 2.57 72 10-12 1.10 64 5.78 38 Nicotine Oil 7-9 .89 52 5.15 66 Nico-Zin Alone 5 .75 44 9.29 0 Difference between analyses made after spraying and before. -80- The nicotine deposited by each application varies from 1.72 mgs. per sq. cm. x 10-3 the Nico-Zin-oil group, taken as 100%, to .75 mgs. per sq. cm. x 10-3 of the same material used alone. the case Only 44% of the nicotine deposited when the two materials were used together was de­ posited when the oil was omitted. The additional nicotine deposited is reflected in the mean percentage of total injury recorded, for the addition of oil to the Nico-Zin effected a reduction in injury of 72% of that resulting from Nico-Zin alone. The intermediate position of the B. L. 155 series is also in keeping with the nicotine deposited and the result­ ant injury. The nicotine-oil group gave control proportionately higher than the analyses of deposited nicotine would indi­ cate, but this control may be due to the use of f% oil in these plots, resulting in effective ovicidal action. It is generally accepted that f% concentration of petroleum oil is the least that is effective as an ovicide, so the J% oil concentration used in the Nico-Zin series did not have this effect. Therefore it is apparent in the data presented that the control of codling moth, all types of injury, is directly proportional to the nicotine deposited by each application, except when oil is included in the application in ovicidal concentration. Corroborative Results on Baldwin. Soy, and Ben Davis. The data obtained by examining the fruit from count trees of the three varieties in the old orchard, Baldwin, Spy, and B en -81- Davis, are presented for each variety in Tables XX, XXI, and XXII, then all varieties are combined in Table XXIII. In general it may be observed that greater varia­ tions occur in the data from these older trees. This is to be expected for the smaller number of replications in­ troduces sampling errors that are not reduced, and may be magnified, by counting large numbers of fruits from each tree. In analyzing these data the results obtained in the carefully randomized McIntosh block should be used as the standard, and the general consistencies are most valuable results, rather than the wide variations. In the Baldwin variety, Table XX, the proportion of deep entries is generally lower than in the McIntosh, Table XV, and the proportion of stings to worms is higher. is characteristic of a less susceptible variety. This The con­ trol achieved by the different schedules on this variety is much the same as In the McIntosh, though the differences between the Nico-Zin-oil and nicotine-oil series and the B. L. 155 and Nico-Zin alone series is not as great. The proportion of shallow entries remains high in the lead ar­ senate plot. The results of the Spy counts, Table XXI, show very close relationship with those from the McIntosh. This sus­ ceptible variety again demonstrates the value of oil with Nico-Zin, the control in Plots 1-4 being far better than Plot 5. Plot 12 gave the best control of any of the B. L. 155 series, but In general the summary of plot relationship Is the same as that recorded on McIntosh. -82- TABLE XX CODLING MOTH INJURY - BALDWIN - MASON, MICHIGAN 1935 Plot No* 1 2 3 4 No. Apples 1339 2111 1910 2118 .% Entries Replication 1 2 Mean % Deep Shallow 1-57 5.38 ----- 1.57 5.38 Deep Shallow 1.18 3.32 ---- 1.18 3.32 Deep Shallow .63 1.83 -- -- .63 1.83 Deep Shallow .90 4.06 ---- .90 4.06 5 4982 Deep Shallow 2.20 7.42 .87 4.28 1.54 5.85 6 3112 Deep Shallow 1.25 6.77 .56 13.71 .91 10.24 7 991 Deep Shallow .34 4.51 1.20 5.78 .77 5.15 8 1138 Deep Shallow .54 5.79 7.01 18.63 3.78 12.21 9 2957 Deep Shallow 1.39 3.40 .95 4.59 1.17 4.00 10 3849 Deep Shallow 1.71 8.95 .93 4.47 1.32 6.71 11 4887 Deep Shallow 1.20 5.81 .55 3.11 .88 4.46 12 4879 Deep Shallow 2.73 5.69 1.36 5.41 2.05 5.55 13 5154 Deep Shallow .83 4.61 1.49 6.35 1.16 5.48 -83TABLE XXI .CODLING MOTH INJURY - SPY - MASON, MICHIGAN 1935 Plot No. No. Apples % Entries Replication 1 2 Mean % 1 4730 Deep Shallow 1.17 5.84 2.03 3.04 1.60 4.44 2 3412 Deep Shallow 1.79 3.72 1.99 4.65 1.89 4.19 3 2301 Deep Shallow .50 4.71 .72 8.94 .61 6.83 4 702 Deep Shallow 3.18 5.31 3.69 4.62 3.44 4.97 5 4095 Deep Shallow 3.75 14.54 4.51 15.77 4.13 15.16 6 1605 Deep Shallow 1.00 17.01 7 1868 Deep Shallow 1.34 4.03 1.16 5.52 1.25 4.78 8 2132 Deep Shallow 1.12 4.73 1.81 3.62 1.47 4.18 9 4244 Deep Shallow .47 2.22 1.84 3.23 1.16 2.73 10 1918 Deep Shallow 2.14 8.76 9.34 16.54 5.74 12.65 11 2778 Deep Shallow 1.79 13.87 4. 46 7.38 3.13 10.63 12 5583 Deep Shallow 2.13 6.47 3.21 9.03 2.67 7.75 13 1004 Deep Shallow 3.39 11.16 1.00 17.01 3.39 11.16 -84- TABLE XXII CODLING MOTH INJURY - BEN DAVIS - MASON, MICHIGAN 1935 Plot No. No. Apples % Deep Entries % Shallow Entries 1 2574 .08 1.40 2 1298 .46 .77 3 2188 .09 .82 4 1598 0.00 .38 5 1063 1.51 2.16 6 13E>2 0.00 8.43 7 2398 .25 .92 8 1648 .24 .97 9 1953 .31 .36 10 1682 .36 1.31 11 2896 1.66 2.76 12 1426 .56 2.38 13 1248 .30 2.88 -85- TABLE XXIII CODLING MOTH INJURY - MASON, MICH. 1935 1— Plot No. McIntosh % Entries Baldwin Mean % Spy Den Davis 1 Deep Shallow 1.15 1.03 1.57 5.38 1.60 4.44 .08 1.40 1.10 3.06 2 Deep Shallow 1.80 1.69 1.18 3.32 1.89 4.19 .46 .77 1.33 2.49 3 Deep Shallow 1.03 1.06 .63 1.83 .51 6.63 .09 .82 .59 2.64 4 Deep Shallow 1.26 .80 .90 4.06 3.44 4.97 0.00 .38 1.40 2.55 5 Deep Shallow 4.83 3.66 1.54 5.85 4.13 15.16 1.51 2.16 3.00 6.71 6 Deep Shallow 1.50 9.61 .91 10.24 1.00 17.01 0.00 8.43 .85 11.32 7 Deep Shallow 1.74 2.82 .77 5.15 1.25 4.78 .25 .92 1.00 3.42 8 Deep Shallow 1.76 1.95 3.76 12.21 1.47 4.18 .24 .97 1.81 4.83 9 Deep Shallow .79 1.20 1.17 4.00 1.16 2.73 .31 .36 .86 2.07 10 Deep Shallow 1.19 2.02 1.32 6.71 5.74 12.65 .36 1.31 2.15 5.67 11 Deep Shallow 4.22 3.52 .88 4.46 3.13 10.63 1.66 2.76 2.47 5.34 12 Deep Shallow 3.26 2.57 2.05 5.55 2.67 7.75 .56 2.38 2.13 4.56 13 Deep Shallow 1.16 5.48 3.39 11.16 .30 2.88 1.62 6.51 - 86 - The results from the Ben Davis variety (Table XXII) are from only one replication in each plot. The control was excellent, for the trees were easily sprayed and the variety resistant to injury. The data have little significance when considered alone, but when compared with the other results the same relationship of the plots is apparent. Discussion of Relative Control Table XXIII includes a summary of the control of each of the two classes of injury on each variety, and the aver­ age figure for all varieties. A s the lead arsenate was included for a standard of comparison, the control achieved by this material should first be considered. The mean percentage of deep entries was always comparable with the most effective schedules, but the mean percentage of shallow entries usually exceed­ ed that obtained by the least effective schedule. The mean percentage of deep entries on lead arsenate sprayed plots (all varieties) is .85, that of shallow entries Is 11.32. The soluble and non-volatile series, of ^ico-Zin, in plots 1 to 5, gave as good control of deep entries as the lead arsenate schedule, and much better control of shallow entries, except when oil was omitted (in Plot 5.) The in­ clusion of oil was very important, its omission usually resulted in twice to three times as much injury. The soluble and volatile series, nicotine sulfate-oil emulsion, resulted in a high percentage of clean fruit, not significantly less than the Nico-Zin oil plots. The insoluble and non-volatile series, bentonite-nico- - 87 - tine combinations called B. L. 1 5 5 ’s, have been com­ pared without consideration of rather large, but incon­ sistent, variations within the series. Omitting this variation, the control by this series surpassed that of the Nico-Zin used alone, but the percentage of each class of injury was greater than in other nicotine schedules. Compared with lead arsenate, it gave fairly significant increases in injured fruit. Plot 13, in the old orchard only, was a schedule com­ bining bentonite and nicotine in a tank mixed method, but no remarkable control is indicated. An objectionable gel­ atinous bentonite residue persisted until the fruit was harvested, defeating the purpose of this material as an in­ secticide. SUMMARY In summary, the season of 1935 was characterized by normal temperatures and ample rainfall. The codling moth population was unfavorably affected by climatic conditions, but a moderate population was established. Three series of materials were tested, under varying conditions. The first, containing the soluble and non-volatile ma­ terial Nico-Zin, required the addition of oil (in less than ovicidal concentration) to effect excellent control of deep and shallow codling moth injury. The addition of oil result­ ed in decrease in color, and increase in rate of dropping. The material has great promise, if an innocuous spreader can be developed. The second series, combining nicotine sulfate (Black - 88 - Leaf 40) with summer oil emulsions, gave excellent control of codling moth Injury. No reduction in color, but an Increase in rate of dropping, was observed. The nicotine deposit on this series was so low as to in­ dicate considerable ovicidal effect from the concentra­ tion of summer oil used. Some injury to the fruit resulted from any schedule using oil in all cover sprays, and was accompanied by a reduction in photosynthetic activity of the leaves. The third series, bentonite-nicotine combinations (b . L. 155) gave somewhat poorer control, but in no way injured the fruit or foliage of the tree. Lead arsenate was used as the standard of comparison, and gave excellent control of deep entries, but the high proportion of stings does not seem desirable in the pro­ duction of high quality fruit, even though the death of the worm results. -89CONCLUSIONS INDICATED BY EXPERIMENTAL RESULTS. Tests of schedules utilizing the organic insecti­ cide nicotine as the active principle were conducted in 1934 and 1935. Under conditions obtaining in Michigan during those two seasons, certain characteristics are demonstrated by the behavior of the different materials. Codling moth control is entirely satisfactory when this material Is used in cover sprays, provided the in­ terval between sprays does not exceed the period of toxi­ city of each application. This affords a substitute in­ secticide for inclusion in the spraying program of grow­ ers who find it impractical to attempt removal of arseni­ cal or lead residues. No environmental effects were encountered in either of the two years which prevented some degree of control with any material tested. However, the data are too lim­ ited to make this a definite characteristic, for some ma­ terials were found Ineffective elsewhere (28), under con­ ditions which might be expected to occur here. It has been shown that it is possible to modify the nicotine volatilization by certain combinations, and that the deposition of nicotine by each spray is proportional to the control of codling moth, except when materials used in modification are in themselves insecticides. A definite effect of sprays applied to thefoliage and fruit has been demonstrated, the toxicity resulting either from some components of the combinations applied, as in the case of sulfur, or oil in the oil-nicotine combination, or from the resultant combination as in the case of Nico-Zin- -90oil, or by the position in the schedule of different materials, as in the case of oil following sulfur ap­ plications. The complete elimination of injury is also possible as in the case of the bentonite-nicotine com­ binations used in 1935. SUMMARY These experiments indicate that no more practical nicotine combination than summer oil and nicotine sulfate was tested. Control of both types of codling moth injury, and production of satisfactory quality fruit was best achieved by this material. HoYrever, other materials will give either better codling moth control, or less injury, or better quality fruit, or higher photosynthetic activity, with resultant increase In quality, or longer retention of toxicity. ACKNOWLEDGMENT Acknowledgment is due the Tobacco By-Products and Chemi­ cal Corporation of Louisville, Kentucky for their financial support of these investigations, and to R. B. Arnold, 0. G. Anderson, and C. C. Taylor, members of that organization, for helpful suggestions in testing these materials. Profess­ or Hutson, of the Michigan State College Experiment Station, has supervised the work since its inception, and for this the author wishes to express his deep appreciation. Acknow­ ledgment is also due W. C. Dutton and C. W. Farish, of the Section of Horticulture, Michigan State College Experiment Station, for assistance in taking leaf counts in 1934; and to Professor Hutson, who arranged the analysis of carbohy­ drates, and to H. C. Beeskow, Section of Botany, who suner- - vis ed the analyses. 91 - Criticism of the manuscript by associates has been valuable. Acknowledgment must also be made of the assist­ ance of those associates who during the course of the experiments in the field, by their attention to details, contributed to the success of the undertaking. -92- LITERATURE CITED (1) Bryant, C. T. The codling moth* Report of the Secfy., Mich* State Pom* Soc. Proc* 1871, 450. (2) Caldwell, J. S. Mean summer or noptimumfT tempera­ tures in relation to chemical composition in the apple. Jour. Agr. Res. 36, 367-389. 1928. (3) Cleveland, C. R. 1934 experiments with newly de­ veloped types of oils for codling moth control. Jour. Econ. Ent. 28, 715. 1935. (4 ) Cook, A. J. Canker worms. Proc. 1876, 43. Mich. State Pom. Soc. (5) __________ Fighting the plpm curculio. State Pom. Soc. Proc. 1890, 193. (6) __________ of warfare. Mich. New insect enemies and new methods Mich. State Pom. Soc. 1880, 136. (7) De Sellem, F. E. Nicotine sulfate for codling moth control. Yakima C Q . Hort. D ept.Ann. Report 1916, 62-72. (8) Diehl, H. C., Lutz, J. M . , and Ryall, A. l . Re­ moving spray residues from apples and pears. U. S. Dept. Agr. farmers Bui. 1687. 1931. (9 ) Doane, H. S. Dusting and spraying with fused ben­ tonite- sulfur . Better F ruit 30 (8), 8. 1936. (10) Driggers, B. F. and Pepper, B. B # Comparative tests of arsenicals, arsenicals with oil, and sev­ eral nicotine compounds used against the codling moth. Jour. Econ. Ent. 27, 249. 1934. (11) _ _ _ _ _ ________________________ Bentonite com­ pounds as agents for the retention of nicotine on apple foliage and fruit in codling moth control. Jour. Econ. Ent. 27, 432. 1934. (12) _______ _ _ _______________________ Further experiments with fixed nicotine compounds in codling moth control. Jour. Econ. Ent. 28, 162. 1935. (13) Dutton, W. C. Spray injury studies. Mich. State College Exp. Sta. Sp. Bui. 218. 1932. (1 4 ) „ _________ •> Hutson,R., and Cation, D. Spraying Calendar. Mich. State College Ag**. Exp. Sta. Sp. Bui. 174, 20. 1934. -93< 15 ) Eustace, H. J., and Pettit, H. Spray and practice outline for fruit growers for 1911. Mich. State Hort. Soc. Proc. 1910, 120. (16) Felt, E. p #^ and tine activators. (17) Fernald, C. H. Mass. Hatch Agr. Ex p. Sta. Bui. 24, 1-7. 1894. (18) Filmer, B. S. Comparative performance of nicotine tannate and lead arsenate againstthe codling moth. Jour. Econ. Ent. 24, 277. 1931. (19) Fisher, R. A. Statistical methods for research work­ ers, 2nd ed. 1928. (20) Flint, W. P. Codling moth control by the use of in­ secticides in Michigan, Ohio, Indiana, and Illinois. Jour. Econ. Ent. 27, 141. 1934. (21) Foster, S. W. and Jones, P. R. ^he life history and habits of the pear thrips in California. U.S. Bept* Agr. Bui. 173. 1915. (22) Gardner, V. R., Bradford, F. C. and Hooker, H. D. Fundamentals of fruit production. McGraw-Hill, 1922, 180. (23) Hartzell, F. Z. The latin square arrangement of ex­ perimental plots. Jour. Econ. Ent.23, 747. 1930. (24) Headlee, T. J., Ginsburg, J. M . , and Filmer, R. S., Some substitutes for arsenic in control of codling moth. Jour. Econ. Ent. 23, 45. 1930. (25) Heald, F. D., Heller, J. R., Overly, F. L #J and Bana, H. J. Arsenical spray residue and its removal from apples. Wash. State Agr. Exp. Sta. Bui. 213, 5. 1927. (26) Herbert, F. B., and Leonard, M. B. Observations on the oil-nicotine combination for the control of codl­ ing moth and other apple insects in the pacific North­ west. Jour. Econ. Ent. 22, 72. 1929. (27) Herbert, F, B. History of the oil and nicotine combina­ tion. Jour. Econ. Ent. 24, 995. 1931. (28) Knight, H . , and Cleveland, C. R. Recent developments in oil sprays. Jour. Ec. Ent. 27, 269. 1934. Brcmley, S. W. ^ests with nico­ Jour. Econ. Ent. 24, 105. 1931. - 94 - (29) Leonard, M. D. Further experiments with nicotine-oil for the control of the codling moth in the Pacific Northwest* Jour. Econ. Ent. 23, 60. 1930. (30) Mclndoo, N. E .9 Simanton, E # Plank, H. K., and Fiske, R. J. Effects of nicotine sulfate as an ovicide and larvicide on codling moth and three other insects. U. S. Dept. ^gr. Dul. 938, 1-20. 1921. (31) Mich. Standard Grades. Mich. State D ept. A gr«, Bureau of Foods and Standards, Bui. 55. (32) Newcomer, E. J., and Yothers, M. A. Experiments with insecticides for codling moth control. U.S. Dept. Tech. Bui. 281. 1932. (33) Pettit, R. H. The codling moth. Sort. &oc. Proc. 1903, 198-200. (34) Snedecor, G. w. Calculation and interpretation of analysis of variance and covariance. Collegi­ ate Press, Inc., Ames, Iowa, 1934. Mich. State