TIMELY TURF TOPICS

Issued By The
UNITED STATES GOLF ASSOCIATION GREEN SECTION

ROOM 307, SOUTH BUILDING 

PLANT INDUSTRY STATION 

BELTSVILLE, MD.

2,4-D,—WHAT IS IT? 2,4-D is an organic acid (2,4-dichlorophenoxyacetic acid) which be­
longs to the group of chemicals which have been demonstrated as affecting the growth of 
plants in various ways and hence have been called plant growth regulators, or, by the 
layman, plant hormones. It is not directly soluble in water and must therefore be put 
into solution in one of several different ways. Either it must be dissolved in a carrier 
in which it can be dispersed in water; a soluble salt of it must be made; or it must be 
mixed with another salt or alkali which, when added to water, win react with the 2,4-D 
to make its soluble salt. During this spring and summer all 3 of these types of prod­
ucts have been tested by the Green Section in cooperation with the National Capital Parks 
and all of them have been found to be reasonably effective. In all tests 2,4-D in Carbo­
wax has been used as the standard of comparison. So far as herbicidal effectiveness is 
concerned the 2,4-D in Carbowax has not been consistently surpassed by any of the products 
so far tried. In the greenhouse during the winter months various solvents were tested in 
cooperation with Dr. Paul 0. Marth of the Hormone Project in the Plant Industry Station, 
with the result that Carbowax 1500 was found to be among the very best of those which are 
readily available commercially because (1) it readily dissolves the 2,4-D and then dis­
perses it in water very satisfactorily; (2) it is not injurious to the grasses, even to 
creeping bent maintained at putting green height; and (3) it gave evidence of favorably 
influencing the effectiveness of the 2,4-D.

RECOMMENDED RATE OF APPLICATION OF 2.4-D: As discussed in the November issue of HUKU 
TURF TOPICS the rate of application of 2,4-D which the Green Section recommends for use on 
turf is an application of 5 gallons of a 0.1J solution of 2,4-D. , This necessitates the use 
of 2 ounces of the 2,4-D for every 3,000 square feet or 1 and 3/4 pounds to an acre. Since 
uniform coverage is an important factor, the use of 5 gallons of solution to 1,000 square 
feet or 200 gallons to the acre is recommended. Bien using commercial products which have 
2,4-D as their active ingredient the method of preparation of spray solution recommended 
by the manufacturer should be followed. The concentration of the solution, however, and 
the amount applied per acre can readily be calculated on the basis of the aforegoing fig­
ures, by using the manufacturers* statement of the percentage of 2,4-D which the product 
contains.

It has been the Green Section’s experience that some weeds may require 2 or even
3 times as much 2,4-D whereas others may require much less than the recommended 5 gallons 
of a 0.1J solution (2/3-ounce of 2,4-D) to 1,000 square feet. This seems to be a generally 
satisfactory application, however, and therefore the Green Section recommends it as a 
starting point in determining the effectiveness of 2,4-D on turf weeds under any particu­
lar set of conditions. Bluegrass and Bermuda grass have been treated during this season 
at rates up to 6 times the recommended rate without any injury whatsoever to the grass, 
so there should be no question of danger to these grasses if the concentration must be 
elevated to kill particularly difficult weeds.

Some weeds, such as chickweed, which form dense mats of vegetation have to be

retreated after 2 or 3 weeks’ time in order to cover vegetation which was not reached 
with the first application.

July, 1915

RESPONSE OF TURF WEEDS TO 2,4-D: Many plants are extremely sensitive to 2,4-D in very 
small quantities. Others are quite resistant to it. In order to determine which of the 
turf weeds are sensitive to it and can therefore be readily killed by it, it has been 
necessary to run .a large number of tests on the common turf weeds as they occur throughout 
the various seasons. In the early exploratory experiments last fall, time and labor did 
not permit the testing of 2,4-D on a large number of weed species.

In March of this year, however, in cooperation with Mr. Horace V. Wester of the 
National Capital Parks the Green Section initiated a comprehensive test of 2,4-D and many 
proposed formulations of it on a wide variety of turf weeds as they occurred throughout the 
season on the turf of the National Capital Parks. The turf was composed of numerous gras­
ses and maintained at various heights. These weeds together with those which were tested 
last fall in the vicinity of Washington, D. C., as well as those on which reports have been 
received from other sections of the country, (particularly Florida) are listed below, ar­
ranged alphabetically according to their common names. In order that there may be no ques­
tion as to the identity of the weeds when referred to by their common names the scientific 
names are included in parenthesis for each of the weeds. In some cases the species have 
not been determined, in which case only the name of the genus is given.

Bugleweed (AJuga reptans) 
Buttercup (Ranunculus sp.) 
Carrot, wild (Daucus Carota) 
Catchfly (Silane sp.) 
Chaerophyllum (Chaerophyllum procumbens) 
Chickweed, common (St ell aria media) 
Chickweed, mouse-ear (Cerastium sp.) 
Cinquefoil (Potentilla, sp?) 
Clover, white (TrJ/^UUffl reoens) 
Crabgrass (Digitaria sp.) 
Cress (Bsrbflrea vulgaris)
Cress, swine (.CgrPAQWAfi dl&syjg)
Daisy, ox-eye (Chrysanthemum Leucanthemum) 
Dandelion (Taraxacum officianale) 
Dandelion, false (Krigia virginica) 
Dichondra (P.ioX^Ea reoens)
Dock (Rumex sp.)
Dog fennel (Anthemis Cptula)
Fleabane (Erigeron canadensis)
Gill-over-the-ground (N^gtfl hfidfixafififl)
Goosegrass (Bleusine indica) 
Heal-all (Prjjaellfi vulgaris) 
Henbit (La^LUffl amolexicaule) 
Knotweed (Polygonum aviculare)
Lambs-quarters (Chenopodium album) 
Lespedeza (LgfigQdgzfl striata) 
Lippia (Linpia sp.)

xx Mustard, wild (Brassica sp.) '

0 Nimbiewill (Muhlenbergia Schreberi)

xx Onion, wild (Allium sp.)
0 Paspalum (Paspalum sp.)

xx Pennywort (Hydrocotyle bonariensis)
xx Pennywort (Hydrocotyle rotundifolia)
xx Pennywort (Hydrocotyle umbellate)
xx Peppergrass (Lepidium virginicum)
xx Plantain, broad-leaf (Plantago major)
xx Plantain, narrow-leaf (Plantaga Lanceolate)
xx Purslane, milk (Euphorbia maculate)
xx Pussy toes (Antennaria J2>flv^lhifolift) 

Ragweed (Ambrosia ftFtwlsUfplXa)

0 Sedges (Cyperus spp.)

xx Shepherds-purse (Capsella Bursa-pastoris)

x Smartweed (Polygonum Persicaria)
x Sorrel sheep (Rumex Ac.e.tosella)
0 Sorrel, wood (Oxalis sp.)

xx Speedwell (Veronica TpixmQfQrtll)
xx Speedwell, rock (VerQatffift arvensis) 

Sticktight (Bidens sp.)

xx Strawberry, false (Duchesnea indica)
xx Veronica, ivy-leaved (Veronica hederaefolia)

0 Violet (Viola sp.)

xx Whitlow grass (Draba verna)
Wormwood (Artemisia sp.)
Yarrow (Achillea Mjj,lX?XQ3A]m)

In this list the weeds which have been satisfactorily eradicated at any time as 
a result of applications of 2,4-D at the recommended rate are preceded by the symbol Mxx". 
Attention should be drawn to the fact that no attempt is made to indicate in this table the 
season of the year in which the weeds have been most satisfactorily eradicated. This ques­
tion of the seasonal variation in the sensitivity of the weeds is discussed in another sec­
tion of this issue. The weeds which have required much higher rates of application for 
eradication are marked with a single x. Those which have definitely been strikingly resis­
tant to the 2,4-D to the place where it has not been possible to satisfactorily eradicate 
them at the rates used, are marked with a zero. The remaining weeds are ones on which the 
evidence to date is not sufficient to justify a conclusion. Wild onion has been marked 
with the "xx" because it was removed entirely from the turf in the spring, although it is 

July, 1945

T. T. T. 3

recognized that the final story concerning complete eradication cannot be told until the 
bulbs have had a chance to sprout again this fall or next spring.
It may be stated that various members of the mustard family which are not listed
A 
^are because they were not present in sufficient numbers did occur on various plots and in 
all instances they were killed. All members of the mustard family so far treated in turf 
have been eradicated with the 2,4-D.

To those who have used other herbicides, the active ingredient of which is an 
arsenical, chlorate, one of the dinitro compounds, etc.; several important contrasts be­
tween the activity of these two materials and that of 2,4-D should be emphasized. 2,4-D 
acts more slowly but much more completely on the plants as a whole if they are sensitive to 
it. In other words, if the 2,4-D affects the growth of the plants at all, its effect on 
the root system is likely to be just as severe as its effect on the tops. Since the 2,4-D 
does not produce a burning of the tops accompanied by a resulting starvation of the roots 
but rather an effect on the growth of the entire plant, it is readily understood why it 
frequently takes from 2 to 3 weeks to produce ultimate death with the 2,4-D.

The first symptom which may occur in as short a time as 24 hours or which may in 

the case of some weeds under some conditions require 5 or 6 days to appear, is a curling 
of the leaves or the petioles. This is followed by a yellowing of the green tissue and 
eventual death and decomposition after 2 or 3 weeks’ time. As is indicated elsewhere in 
this issue the speed with which the effect becomes evident depends on the growing condi­
tions at the time and on the weed itself and its sensitivity to.2,4-D. For the most part 
most weeds may be expected to react most violently at the time of year in which they are 
growing rapidly. In the case of some weeds such as dandelion, physiologically mature 
plants have been more easily killed than seedlings.

Much can be learned from preliminary tests with the material under any particular 

set of conditions before undertaking large-scale applications. Therefore such "on the 
spot" tests are strongly urged before large scale operations are initiated.

TARGE SCAIE APPLICATIONS OF 2,4-D NOTABLY EFFECTIVE AT THE 0. S. NAVAL ACADEMY: Mr. A. E. 
Babbitt. Agronomist in the Bureau of Aeronautics of the Navy Department, informed the Green 
Section that the Navy Department applied 2,4-D in Carbowax in May of this year to 35 acres 
of turf at the U. 8. Naval Academy at Annapolis, Md., with outstandingly successful re­
sults. Six acres of this area were seriously infested with dandelion at the time of appli­
cation. When Mr. Rabbitt inspected the treated area Appmxl mwtply a month later only 9 
dandelion plants could be found in the entire 6 acres of the parade grounds. In the re­
maining acreage in the athletic area which was heavily infested with narrow-leaf plantain 
the treatment resulted in approximately a 9bX control. One small area of approximately 
1/2-acre will require a second application. The spray solution was prepared according to 
the directions published in the November, 1944, issue of TIMELY TURF TOPICS, 1-3/4 pounds 
of 2,4-D being dissolved in 8 pounds of Carbowax, which in turn was dispersed in 200 gal­
lons of water and sprayed on an acre of turf.

WHEN TO USE 2,4-D: When the weed population in turf reaches a sizable proportion it is 
advisable always to remove those weeds at a time when the turf grasses can most easily be 
encouraged to fill in the bare areas left following the removal of the weeds. Therefore 
in most cases it will probably be advisable to remove the weeds with 2,4-D in spring or 
early fall in order that the turf may be reseeded if necessary and certainly fertilized 
without running the risk of fertilizing the weedy grasses. With spring and fall applica­
tions of 2,4-D it is possible to distribute the seed and fertilizer before applying the 
2,4-D thus enabling the grabs seedlings to develop as the weeds disappear. In some in­
stances when one or more of the predominant weeds happen to be, like broad-leaf plantain, 
decidedly most sensitive in midsummer, it may be necessary to treat at that time. Midsum­
mer treatments, particularly in crabgrass areas, however, are likely to result in the crab­
grass merely replacing the weeds which 2,4-D removes. If on lawn areas it is desirable 
to remove weeds such as dandelion and plantain without too seriously injuring clover, how­
ever, midsummer applications may be advisable since it has been demonstrated that these 
weeds may be removed from turf in the midsummer at the recommended rate without completely 
killing the clover. It will be recalled that it has been stated elsewhere in TIMELY TURF 
TOPICS that clover has been most easily killed in the fall and spring.

July, 1945 

T. T. T. 3

EFFECT OF CLIMATIC FACTORS ON HERBICIDAL PROPERTIES OF 2,4-D: Tests have been made during 
this season to determine the influence of shade, rainfaill, and temperature on the effective­
ness of 2,4-D. Where comparable series have been established in open sun and in partial 
Ijhade it has been demonstrated that the response of broad-leaf plantain, dandelion, and clo- 
iJar has been more prompt in the open sun than in the shade. However, the eradication after 
a month’s time was just as complete in the shade as in the open sun. In fact in the case of 
clover the eradication was much more perfect in the shade. It has not yet been demonstrated 
whether this effect was due to a light factor or to a lower average temperature on the shad­
ed plots than in the sun.

It has definitely been demonstrated that temperature affects the effectiveness of 

2,4-D, the optimum temperature for eradication varying with different weeds. Last winter, 
for instance, flats of pennywort, heal-all and chickweed were growing in a greenhouse main­
tained at 60 to 65°0. They were treated with 2,4-D and its sodium and ammonium salts and 
maintained in this greenhouse at the same temperature for 10 days. The chickweed in this 
time curled, began to yellow end showed signs of death, which eventually was complete at 
this temperature. The pennywort and heal-all gave practically no evidence of having been 
treated with 2,4-D over this 10-day period, whereupon they were moved into an 80° greenhouse. 
At the higher temperature the effect of the 2,4-D became evident within a few hours and after 
4 or 5 days the flats of both weeds were dead. The chickweed on the other hand died while 
maintained in the cooler greenhouse.

Unlike other herbicides, the effectiveness of 2,4-D, particularly when it is ap­
plied in Carbowax, is not seriously reduced by heavy rains following as close as 1/2-hour 
after application. When applied to wide-leafed weeds such as dandelion, plantain, and the 
mustard family, the effectiveness of neither the 2,4-D-Carbowax solution nor the soluble 
formulations of 2,4-D has been reduced by rains immediately following the application. In 
fact, in one series of tests in which the potassium, sodium, ammonium, and calcium salts 
were being compared with each other and with 2,4-D-Carbowax it was drizzling throughout the 
time in which the applications were made and a heavy rain followed within a few hours after 
application. In spite of this the treatments resulted in almost complete control of dande­
lion, broad-leaf plantain and clover - the predominating weeds in the turf. In another 
series, however, when the soluble formulations as well as the Carbowax solution of 2,4-D 
were applied to the very small leaves of young seedling knotweed and a drenching rain fol­
lowed within 30 minutes after the last application, the effectiveness of the soluble formu­
lations was definitely reduced by the rain. The 2,4-D in Carbowax, however, resulted in a 
very satisfactory control of the knotweed in spite of the rain. No well controlled tests 
have yet been made of the influence of soil moisture on the effectiveness of 2,4-D but some 
observations indicate that higher rates of application may be necessary when soil moisture 
content is unusually low.

SEASONAL VARIATIONS IN WEED SENSITIVITY TO 2,4-D; Tests with 2,4-D have been under way 
by the Green Section for 11 months. Results from these tests have indicated in some cases 
a striking fluctuation in the response which certain weeds make to applications of 2,4-D, 
at various stages of growth, and in different seasons. Broad-leaf plantain, for instance, 
was only slightly curled by treatments made last fall at the standard rate of 5 gallons of 
a 0.1J solution to 1,000 square feet, whereas this summer there has been a complete eradica­
tion of this species on many series of plots established through May, lune and July, not 
only with the 2,4-D in Carbowax but also with most of the formulations under test. Wild 
onion also was apparently untouched by most fall applications whereas applications made in 
March and April of this year resulted in very striking immediate effects. The onion tops 
turned purple, were curled severely in such a manner that they lay on the ground prostrate 
although very turgid. When the tops were removed by cutting, completely chlorotic shoots 
appeared, which in turn were removed by the mower. Observations this fall and again next 
spring on these treated plots will be necessary before any statement can be made concerning 
the permanent eradication of the onions from the turf.

Quite to the contrary, clover which was completely eradicated by treatments at the 
p!bove mentioned rate last September and October as well as in March and April of this spring 
has required a much higher rate or repeated applications at the above rate for complete con­
trol in May, June and July applications. Shepherds-purse, cress, and various other members 
of the mustard family, as well as narrow-leaf plantain, have been completely eradicated with 
applications made throughout the growing season from late August to the present time. Even

July, 1945

T. T. T. 4

applications made to dormant narrow-leaf plantain in December end January, although they 
gave no evidence of immediate effect caused the plants to die when growth was initiated 
in early spring. Generally speaking, however, it seems that the control is most efficient 
|shen applications are made at the time of year in which the weed concerned is growing most 
actively.

In dandelion there seems to be some evidence that physiologically’ mature plants,— 

that is, plants which are in flower or seed, 'are much more effectively eradicated than are 
plants when they first initiate growth in the spring. Applications in the National Capital 
Parks made on March 12 to dandelion plants which had developed considerable foliage and yet 
showed no signs of flowering were temporarily curled and yellowed but were not killed, where­
as applications made the same day to plants which, because of being in a sheltered area, 
were in bud and flower, resulted in complete eradication. All subsequent treatments of 
dandelion this year, as well as tests last fall have resulted in an outstandingly complete 
eradication of dandelions.

CAUTION.’ CLEAN SPRAYERS THOROUGHLY FOLLOWING APPLICATIONS OF 2r4-D: Liany vegetable and or­
namental crops are extremely sensitive to very minute quantities of 2,4-D. Therefore when 
using spray equipment for spot treating with 2,4-D or for small-scale tests of this material 
it is vitally essential that that equipment be thoroughly cleans. before it is used for 
spraying such plants as tomatoes, potatoes, roses, etc. It has been demonstrated that even 
after rinsing with hot water, hand spray equipment which has been used for 2,4-D, there is 
frequently enough left in the spray tank to seriously injure tomato plants sprayed subse­
quently. The best answer to this danger is to use spray equipment which is reserved exclu­
sively for applying 2,4-D. If, however, the equipment is never used for the protection of 
vegetation other than turf this precaution is not necessary. For thorough cleaning of the 
spray equipment following the use of 2,4-D it is advisable to wash it with hot soap suds 
and rinse repeatedly with hot water. A solution of trisodium phosphate (1 pound in 25 gal­
lons of water) is perhaps even better than soap suds for the removal of 2,4-D from spray 
equipment.

DUST VS. STRAY APPLICATIONS OF 2,4-D: All golf courses do not have the necessary spray 
equipment for large-scale spraying of fairways and rough in order to remove weeds. There­
fore it seemed desirable to determine whether or not dusts can be prepared which will be as 
Qf’ficioD.'t as the spray applications of 2,4-D which have been discussed in the November is­
sue of TIMELY TURF TOPICS as well as in other portions of this issue.

In preliminary experiments last fall in which the 2,4-D was applied dry mixed with 

fertilizer or sand it was found that narrow-leaf plantain was not satisfactorily killed ex­
cept where amounts of 2,4-D approximating 18 to 20 times that which is applied in 5 gallons 
of a 0,1$ solution were used. Moreover, it is very uncertain how such relatively large 
amounts of 2,4—D applied to the soil might affect the fertility of the soil. Therefore the 
possibility of applying the 2,4-D in this way was at least temporarily given up. It should 
be mentioned, however, that within a few days after the dry mixture had been applied a series 
of heavy rains caused some washing on these plots.

Later in the greenhouse, dusts were applied to clover-grass mixtures growing in 

flats to determine both the tolerance of the grass end the sensitiveness of the clover. 
The dusts were prepared in various carriers including Pyrax, Fuller's earth and Cherokee 
clay. The requisite amount of 2,4-D was dissolved in alcohol and nixed with the dust car­
rier to form a thick paste. This in turn was dried, finely pulverized, thoroughly mixed, 
and applied at the rate of 4 pounds to 1,000 square feet. The dust was prepared with con­
centrations of 2,4-D varying from 0.5$ to 10$. The 1$ dust furnished the sane amount of 
2,4-D when applied at the rate of 4 pounds to 1,000 square feet as does 5 gallons of a 0.1$ 
solution. The 1$ dust, although it resulted in a slight immediate cnrling p-nd ypilowing 
of the clover, did not permanently injure it whereas the 2.5$ dust killed approximately 85$ 
of the clover and did not injure the bluegrass in the flat. The 5$ dust gave a 95$ kill 
of the clover but also resulted in considerable injury to the grass for the first 2 to 3 
weeks following the treatment. Six weeks following treatment, however, there was no notice­
able effect on the grass, which apparently had recovered completely. The 10$ treatment re­
sulted in a decidedly thin turf although it of course gave a complete kill of all clover 
present. Following these tests 1$ and 2$ dusts were prepared and are being tried in small 

July, 1945

T. T. T. 5

scale plots in the field this summer but results are not yet in. If dusts are to be used 
they should be applied when the grass is wet with dew in order to hold the active ingre­
dient on the leaves a sufficiently long time to permit its being absorbed by the plent 
tissue.

The major concern in applying 2,4-D in dust form is that the dust flies and 

therefore may be more injurious to sensitive ornamental plants bordering the fairways than 
are sprays likely to be. Also before 2,4-D dusts are to be used in a large-scale mp-nnar, 
tests should be made on any possible effect of the inhalation of such dusts.

COMMERCIAL SOURCES OF 2,4-D: 2,4-dichlorophenoxyacetic acid (now commonly known as 2,4-D) 
is not sufficiently soluble in water to permit its use in aqueous solution without the use 
of a carrier. Several of these carriers are being used by various manufacturers as evi­
denced by the following products which are now available at widely different costs.

’’Chipman 2,4-D Weed Killer*1

Manufactured by the Chipman Chemical Company, Inc., 6200 N. W., 

St. Helens Road, Portland 10, Oregon

“Concentrate No. 6" (This is a preparation of 2,4-D for mixing with ammonia)- 

Manufactured by Chemical Concentrates Company, 342 Madison Avenue, 

New York 17, N. Y.

"En—Dow-Weed” 

(This is a mixture of 2,4—D end a sodium salt and is

Manufactured by the Dow Chemical Company, Seal Beach, Pittsburgh, Calif.

soluble in water)

“Weedanol Ml" 

(2,4-D in Carbowax 1500 which readily dissolves in
warm water)

Manufactured by Associated Chemists, Inc., North Collins, New York; 

distributed by Eaton Brothers Corpn., Hamburg, New York

“Weedicide" 

(Tablets, which should be dissolved in hot water)
(liquid, in which 2,4-D is made soluble with ’’phenoxysol” 

Manufactured by the Wm. T. Thompson Company, 2727 Hyperion Avenue, 

Los Angeles 27, Calif.

"Weedone" 

(2,4-D in an oil-like base)

Manufactured by the American Chemical Paint Co., Ambler, Pa.

“Weed-Tox 2, 4-D" (This is a mixture of 2,4-D and Carbowax) 

Manufactured by Veith Chemical Company, 1261 Blackstone Avenue, 

Fresno, Calif.

The sodium, ammonium, potassium, and calcium salts of 2,4—D may be dissolved 

directly in water. Various companies in addition to the above, including the E. I« IXiPont 
deNemours & Company, Wilmington, Del.; Merck & Company, Inc., Rahway, N. J".; and the Stan— 
dard Agricultural Chemicals, Inc., Hoboken, N. J.; are using this fact as a basis for 
experimenting this year with 2,4-D products which will be directly soluble in water. These 
latter firms, however, to date have material available only for experimental purposes. To 
those who are interested in preparing their own 2,4—D—Carbowax mi xtures as recommended in 
the Nbvember issue of TIMELY TURF TOPICS it should be stated that the Carbowax 1500 can be 
purchased from the Carbide and Carbon Chemicals Corporation, 30 East 42nd St., New York 
17, N. Y.

'MORE ABOUT 2,4-D in AUGUST ISSUE: Because of lack of space in this issue, additional 
facts concerning the behavior of 2,4-D will be published in the next issue of TIMELY TURF 
TOPICS, which is already in the hand a of the printer.

July, 1945

T. T. T. 6