PEACH BROWN PLOT SETUDiES EN

BERRIEN CQUNTY, MICHIGAN
EN 1949

Thesis for the Degree of M. S.
MiCHlGAN STATE COLLEGE

Bonaid Harry Petersen
1949

This is to certify that the
thesis entitled
Peach brown rot studies in
Berrien county, Michigan

in 1949

presented by
Donald Harry Petersen
has been accepted towards fulfillment

of the requirements for

Master of Sicence degree in Plant Pathology

Major professor

Date—DWer—HW
’

 

PEACH BROWN BOT STUDIES
IN BERRIEN COUNTY, MICHIGAN

IN 1949

By
Donald Harry Egtereen

A.THESIS
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and.Applied Science
in partial fulfillment of the requirements

for the degree of

MASTER OF SCIENCE

Department of Botany and Plant Pathology

Year 1949

Acknowledgements

Introduction . . . .
Literature review .
Canker studies . . .

Introduction .

Methods and materials

Refilllts . o o o

I

INDEX

Fungicidal control of brown rot .

Introduction 0

Blossom sprays

Introduction . .

Methods and materials .

Results

Post—bloom Sprays . . . . . .

Methods and materials .

Realllts o

Pre~harvest sprays

Methods and materials .

Re Bult 8 o

Fungicidal applications under conditions

inoculum

Dipping tests . .

Methods and materials

Results . . . .

Observations . . . .

13

13

13

14

18

18

18

18

19

24

32

39

41

41

42

52

512'

55

58

12

17

17

24
31
4O
38
4O

52

52

57

55

59

Conclusions . . . . . . . . . . . . . . . . . . . . . . , so _ 51

Literature cited

comlusionsoooooooooooo0000000000060‘61

Literature cited

Acknowledgements

The writer wishes to express his appreciation for the appor—
tunity of the counsel and guidance of Mr. Donald Cation, Associate
Professor (Research). Without his initiative and assistance in
planning, the field and laboratory studies would have been most
difficult. And to the Standard Oil Company (Indiana), particular-
ly Dr. C. R. Cleveland, Chief Entomologist, and Mr. George Day,
for making possible the extended field studies, my sincere grat-

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Introduction

The following work discusses various aSpects of peach brown
rot studied during 1949. Laboratory studies and field observa-
tions were made to determine the importance of over-wintered twig
cankers as a possible source of primary inoculum. Field studies
involved the relationship of humidity to the timing of blossom
Sprays, the testing of certain fungicides in the peach spray pro-
gram, and testing various chemicals as post—harvest fruit dips in

an attempt to prevent brown rot in storage and transit.

 

 

 

 

 

Literature Review

The common brown rot of peach encountered in Berrien County is
caused by the fungus W W (Wint) Honey (1). The gener—
ic name is of rather recent acceptance, the former being Sclerotinia.

.L group of species of Sclerotinig having a monilioid conidhal stage
were elevated to generic rank with g. fructicola as the type. The
organism produces its conidial stage on infected parts of suscep-
tible hosts and its apothecial stage on over-wintered mummies partial-

ly buried in the soil.

The primary infection of g. fructicola is largely restricted to I
the blossom blight phase of the disease. The rot of ripening, and in
some cases, green fruit, may also be caused by conidia from over-
wintered mummies hanging on the tree (21) and possibly conidia from

over-wintered cankers.

The possible sources of inoculum for the primary infection are:
ascospores from over-wintered mummies on the ground, conidis from

mummies on the tree, and conidia from twig conkers.

A.remarkable phenomenon is the production and maturation of
ascospores from over-wintered mummies on the ground coincident with
the opening of the peach blossoms. At one time it was thought that
mummies had to be buried for two years in the soil before apothecia
would be produced. However, many workers have demonstrated that
first-year mummies are the most productive under favorable conditions.

Roberts and Dunegan (21) in orperimental trials maintained mummies

 

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which produced apothecia for 6 succeeding years though in diminish,

ing numbers from the abundant production of the first year.

The most favorable position for the mummy in reapect to apo-
thecial production is about half-buried in the soil. If they are
completely buried the apothecia tend to produce imperfect ascospores.
Those resting on tap of the soil seldom get sufficient moisture to

produce apothecia (12).

Peach mummies buried to a depth of 2 or 3 inches and more disin~
tegrate rapidly. In fact, Ezekiel (12) founi, with one exception,
complete disintegration of mummies buried at 3, 8, and 18 inches at
the end of 14 months. ,An entire mummy is not essential for apo-
thecial production. Roberts and Dunegan (21) have observed a frag—

ment of sclerotim 1 cm by 2 mm produce 3 average-sized apothecia.

While it has been felt by many investigators that ascospores
are the most important source of primary inoculum, this has not been
satisfactorily proven in all cases. In 1947 and 1948 Cation (7) ob-
served extremely high percentages of blossom blight (up to 85%) in
orchards that had no apparent source of primary inoculum, i.e. apo-

thecia on the tree or over-wintered mummies on the trees.

Evidence of the over-wintering of the brown rot fungus can be seen
readily after the first spring rains. The surface of the over-wintered
mummies hanging on the trees becomes a mass of conidial tufts or
sporodochia. The ability of the fungus to withstand the adverse condi-

tions of cold and desiccation is due to the formation of a sclerotial

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mat investing the outer tissues of the fruit. Though the majority of
the rotted fruit and subsequent mummies fall to the ground before
spring, some remain on the tree at least until blossoming time. Roberts
and Dunegan (21) state that by late spring they become dry, cease to
produce conidia, and fall to the ground. Several investigators have
shown that conidia produced by these over-wintered mummies on the tree

often cause blossom blight (2, 8, 20).

Conidial production may also occur in the fall of the year on:
newly formed mummies. It has been demonstrated that conidia formed
at this time can survive the winter (22). Bartram (4) demonstrated
the viability of conidia that had passed through.winter temperatures

as low as -32°C.

Active over-wintered twig cankers may represent a third possible
source of spores for initiation of the primary infection.McClintock,
in Georgia, (11) has reported observing conidia en twig cankers
formed during the previous season. However, he later reported failure
to find conidia on blossom blight cankers in their second year (18).
Roberts and Dunegan (21) after 6 years experience in Georgia failed
to find conidia on over—wintered cankers with but one exception.

Smith (22) states that he occasionally saw conidial tufts on branches
of the previous season's growth. Cook (9) in 1919 observed the pro—
duction of conidia from cankers of the previous year and considered
them important in the production of blossom blight. Berkeley (5),

at St. Catherines, Ontario, reports in the spring of 1926 many cankers
active and producing conidia. He found active 2-year old cankers and

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blossoms.

It was once believed that the brown rot fungus after penetrat-
ing through a blighted blossom or rotted fruit to a twig, continued
growing into the larger limbs where it expressed itself as a peren—
nial peach canker (16). However, lillison points out that 97.8% of
the twig cankers caused by blossom blight healed over during the sum—
mer they were formed and only 6.2% of those caused by rotted fruit in-
creased in size during the winter. He found that none eventually re-
sulted in the formation of Valsatype peach cankers. It was apparent
that the brown rot fungus, in spite of its ability to attack wood and
bark, was not a serious factor in the canker complex. However, as
these lesions are Open to invasion by other canker—producing organisms,

these cankers may assume considerable importance indirectly (25).

In later studies, Willison (26) noted that brown rot cankers
are usually delimited within a period of 3 weeks which corresponds to
the time necessary for the host to lay down wood periderm and a
wound-fum barrier. Still further studies by the same author (27)
showed that out of 100 cankers caused by brown rot blossom blight,
80% were either healed or inactive the following year. 12 of the re-
maining 20 had caused twig blight and the twigs had died back nearly
to the parent branch. The few typical cankers that developed were

due to secondary infections of canker-producing fungi (Zalsg Cincta

 

and Z, leucqstoma). These studies are in agreement with those made

by Hildebrand (18).

Blossom Blight Phase

Conidia from over-wintered mummies on the tree and possibly
conidia from holdover twig cankers are distributed by the wind and
rain. They may lodge on the floral parts, germinate, and penetrate
the suscept tissues. The asc08pores are violently discharged from
the apothecium at maturity to be carried by the air currents. Some

of these ascospores may settle on the blossom.

Either conidia from mummies or cankers, or the asCOSpores are
capable of causing blossom infection and this has been demonstrated
many times (15, 9, 17, 18, 20). However, the phenological factors of
humidity and temperature may be of great significance during germina—
tion and incubation of these Spores. Amos (1) showed conidial ger-
mination at 1°C, though growth of the germ tube was very slow.

Ezekiel (11) was unable to observe any difference for the various
strains of the fungus at the cardinal temperatures: minimum 3°C, op~
timum 25°C, and maximum 33°C. weaver (23) found the time required fer
germination on peach petals floated on a 4% sucrose solution varied
with the temperature, from 11 to 12 hours at 5°C and increasingly
shorter periods for intermediate temperatures reaching a minimum of

2% to 3 hours at 20°C. Higher temperatures resulted in longer periods

for germination with no germination at 35°C.

Conidia require precipitated moisture for germination on glass
slides. On blossoms, germination occurred only on the stigma at 80%
relative humidity. 96% was required for germination on the anthers

and petals, and 100% for all other floral parts.

The occurrence of severe blossom blight has most often been as-

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sociated with hot, humid weather. Bares (3), however, studying brown
rot in Oregon, found that the moist, cool weather of early spring was
often favorable for blossom blight infection. It is probable in this
case that the causal fungus may have been 3, 1955. Weaver (23) noted
pistil infection in 10 hours and resulting complete blossom blight in
4 days in a saturated atmosphere at 10°C. 18% hours were required for
petal infection under these conditions, and 34 hours were required for
the fungus mycelium to spread from the petals to the calyx. It was
found that floral parts had to be maintained in a saturated atmosphere
12 hours at 15°C to cause eventual complete blighting if the flower has
been pollinated. If it remained unfertilized, only 16 hours of 100%
relative humidity at 10°C were required for complete destruction.
Given shorter periods in a saturated atmosphere, brown rot lesions de-

veloped in less than 10 to 16 hours but no complete blight occurred.

Weaver (23) states that at humidities of 90% and above the diseas-
ed areas of the petals did not dry out. ALt 80% the lesions were soon
delimited and dried out. He also noted that the production of Spor-
odochia and conidia on the diseased flower parts was dependent on high
humidities. Sporodochia were present on infected stamens 48 hours
after inoculation at 95% relative humidity. No sporodochia were pro-

duced on completely blighted blossoms at 70 and 80% humidities.

The first observations as to the infection courts on the blossoms
were made by loronin (38). He believed that under natural conditions
the stigma was the infection court. Jehle (15) thought that infection
began in the calyx and spread to the stamens and pistil. Roberts and

Dunegan (20) state that any part of the blossom may be invaded, though

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this is disputed by Whetzel (24). Weaver's work (23) on artificial
inoculations agrees with that of Roberts and Dunegan. He states that
at 90% relative humidity, 3 days after the inoculation the fungus had
Spread into the calyx cup from.infection initiated in the petals, se—
pals, or stamens. .After penetration of the stigma, progress down the
style was comparatively slow, but the ovary and finally the entire
blossom blighted. At 80% humidity only the petals and pistils became
infected. At this humidity the diseased petals usually fell off, and
the lesions soon became dry and papery. .A few blossoms blighted com—
pletely after 6 days in this humidity, apparently from pistil infec-

tion.

Throughout Weaver's studies, the greater percentage of complete-
ly blighted blossoms was due to the spread of the fungus mycelium fol-
lowing stamen infection. 'Under most conditions the advance of the
mycelium in the pistil was comparatively slow. Frequently complete
blighting of all flower parts including the calyx was observed while
the style was but partially brown and wrinkled. However, the first

appearance of the disease was most frequently seen on the stigma.

Since all floral parts may serve as infection courts, knowledge
of the percentage of infection at different stages of blossom devel—
0pment has practical significance. In tests conducted by Roberts
and Dunegan (20) partially Opened peach blossoms were not easily in-
fected and some escaped infection entirely. Weaver (23) found that
blossoms in the pink stage of development were not as readily infect-
ed as when they were Open. Sepal infectioriwas very rare in the pink

stage and the progress of the fungus mycelium.from petal infection to

the rest of the blossom occurred only at sustained high humidities.
Large-petaled varieties of peach were less frequently blighted in the
pink stage than small-petaled varieties because of the protection the
petals afforded the stigmas and stamens. No blight occurred at the

closed stage.

It has been noted by most investigators that the young enlarging

fruit usually escapes rot by losing the diseased shuck (21).

Weaver (23) states that blighting of the entire blossom rarely

occurs if inoculation takes place 5 days after pollination.

The first symptom of the disease on the blossom is a faint dis-
coloration of the part infected. Under ideal conditions for the
growth of the fungus the entire blossom soon becomes brown and
shriveled. Masses of ashwgrey conidia are produced over the entire
blossom. The petals, style, and stamens of the blighted blossom.be~
come matted together in a gummy mass, often bending downward. These
masses of gum.and floral parts often remain attached to the twigs for
several weeks and even up into the fall and winter nnrmhs. During
each rain of the season, the gum mass softens and produces a new

crop of sporodochia and conidia.

The Canker and Twig Blight Phase

A.frequent sequal to complete blossom blight is the formation of
twig cankers. These are the result of the fungus mycelium passing

down the peduncle into the tissues of the twig8. Twig cankers may

10

also result from a rotted fruit; however, this more often causes a

complete blighting of the twig rather than the formation of a canker.

Twig cankers resulting from penetration of the fungus from a
blighted blossom appear first as small, brownish, slightly sunken
areas about the base of the peduncle. Subsequent growth of the fun—
gus extends the diseased area up and down the twig from the base of
the peduncle. Growth usually ceases in a few weeks time depending
on the ability of the host to delimit the invaded area. Gum pockets
are formed in the cankers and in rainy periods gum collects on the
surface in drape or masses. As the season advances the sunken areas
of the cankers are ruptured by host callus tissue, leaving a rough,

cankered area on the twig.

The fungus may girdle the twig, killing it above the canker.
This happens most frequently when the fungus penetrates through the
peduncle following fruit rot. However, typical canksrs may result

in such a case.

The cankers on the twigs resulting from blighted blossoms are
known to produce conidia the first summer under conditions of high
humidity thus serving as a source of secondary inoculum for the

fruit rot phase of the disease.
Fruit Rot Phase

The fruit rot phase of brown rot usually results from secondary

spores or conidia. Though fruit rot may result from infection by the

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11

primary conidia of over-wintered mummies hanging on the trees, sec-
conidia from blighted blossoms and from current—season twig cankers

are probably the mostimportant sources of inoculum.

Leaves infected by the peach leaf curl fungus (Egoascus QE-
formans) may also be a source of inoculum as they have been reported

easily infected by g, fructicola (19).

The rot of fruit is most frequently a rot of rips or maturing
fruit, although the green fruit may be rotted when the fungus enters
through.punctures or bruises. Roberts and Dunegan (21) report ob-
serving small green fruit infected from a closely appressed diseased

calyx.

The conidia of the fungus are carried over to the fruit by
wind and rain. Those that land in or near a fresh wound in the
fruit often bring about infection. The most common_wounds are those
made by the plum.curculio adults and larvae and the oriental fruit
moth larvae. Invasion of the ripe fruit may take place through the
unbroken surface primarily through hair sockets but also through the
stomata (10). Smith (22) has shown that the fungus may also enter
the fruit by way of the lesions made by the peach scab fungus

(Cladosporium cgg90philium).

Upon arrival of the conidia on near-ripe fruit, germination is
often rapid. Under favorable conditions this may take place in an
hour and rot symptoms may appear in 18 to 20 hours after germination

(21). Soon after the appearance of the rot, sporodochia are produced

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12

in abundant numbers which serve as a further source of inoculum for

other fruit.

Some of the fruit falls to the ground before it is completely
rotted. Some remains on the tree and becomes thoroughly invested
with fungus hyphae. Such completely invaded fruits may dry and may
either drop or remain on the tree. Those that remain do so because
the fruit stem is killed by the fungus before it produces an ab-
cission layer. The completely rotted and shriveled fruit on the tree
and on the ground are the so-called mummies and are important in
initiating the disease the following spring through production of

conidia or ascospores.

l3

CANKFR STUDIES

Introduction

In certain orchards where severe blossom blight occurred
ascospores and conidia from over—wintered mummies, the two common
sources of inoculum for blossom infection, were not present. In
these instances over-wintered twig cankers were suspected of being
the major source of inoculum. Therefore, laboratory studies were
undertaken to determine the importance of twig cankers as a source

of conidia for primary infection.

Cation and Dunegan (6) in isolation studies conducted in 1948
showed that 73% of over—wintered cankers contained E, fructicola.
They also reported sporulation of the cankers in the laboratory in
moist chambers. Laboratory studies were undertaken in 1949 to en-

large upon these observations.
Methods and Materials

During February, 1949, cankered peach branches were collected
in southwestern Michigan and brought to East Lansing. On February
16, branches of Elberta peach were cut from trees near South Haven
and on February 20, branches of Halehaven peach were collected near
Sodus. The day after collection the cankers were subjected to
treatments of varying moisture and temperature to determine conidial

production under controlled conditions.

1h
Results of Canker Studies

A group of Elberta peach branches, containing 123 cankers typ-
ical of those caused by the brown rot fungus, were subjected to 9
hours of wetting and then placed in a saturated atmosphere with a
temperature 0f 15° to 18°C. The majority of these cankers were on
2—yeer old wood resulting from the invasion of the fungus through
blighted blossoms of the previous year. However, there were some

cankers on 3 and h-year old wood.

Conidia were first observed on the cankers after 9 hours in a
saturated atmosphere. At lb hours, 6.5% of the conkers were pro-
ducing conidia. After #8 hours, a maximum of 47.1% showed sporo-
dochia. These data are presented in TEFLE I. The sporodochia were,
With but one exception, produced on the lip of the canker rather
than in the center. Sporodochia were also produced in some cases
on tips of old fruit peduncles and on blighted twigs. Some of the

fruit peduncles showed evidence of the fungus after 5 hours in a

saturated etmOSphere.

TABLE I. Sporuletion observations of 123 conkers in a saturated

atmosphere, temperature 15 to 1300.

 

 

Time in saturated Total No. of cankers % producing sporodo-
g:gtmosphere _producing sporodochia chia. Total 121
lb hours E 6.5%
21; " 12 9.Cf§§
35 n 2'»: 22.8%
he " 58 ' was

 

 

 

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15

A study was then made to determine the percentage of cankers of
different age groups that were capable of producing sporodochia under
laboratory conditions. Cankered branches of Elberta peach were col-
lected, the uncankered wood cut off just beyond the visible limits of
the cankers, and the cankers placed in water for 9 hours. They were
then removed and placed in a saturated atmOSphere at a temperature of

21°C.

Results of this study showed that 1-year old cankers were the
most active in producing sporodochia. At 23 hours in a saturated
atmosphere, 75% of the l-year cankers and 69% of the 2-year cankers
were eporulating. None of the 3 and 4—year old cankers had produced
conidia at this time, the 3—year cankers requiring over 23 hours in
a saturated atmoSphere and the 4-year cankers needing over 46 hours
for conidial production to start. 9.5% was the maximum number of 4-
year cankers to produce conidia while 22.2% of the 3-year cankers

eventually produced conidia. TABLE II tabulates these data.

TABEE II. Sporulation observations of various aged l"cankers in a

saturated atmosphere, temperature 21°C.

 

 

 

 

 

 

l-year canker 2-year canker 3—year canker 4—year canker

Time in ‘(tptal of 32) (total of 2Q) (total of 27) (tptal of 26)
saturated No. %‘ No. % No. dT' No.

atmosphere active active active active active active active active

7 hours 8 25% 2 7.7% o ——— o ___

23 " 24 75% 18 69.2% o —-- o ___

45 . 24 75% 18 69.2% 6 22.2% o --_

70 n 24 75% 18 59.2% 5 22.2% 2 9.5%

 

* Cankers were presumed to be 1 year younger than the age of that
portion of the branch on which they were borne.

16

In all cases the cankers were held longer than 70 hours but there
was no increase in the numbers producing sporodochia. In many cases
in the 3 and 4-year old groups, callus tissue formation was quite
extensive. The percent difference in sporulation between the l and
2—year old groups was not great but there was a large drop between
the 2 and 3-year old groups, 69.2% to 22.2%. As a source of conidia
for the primary cycles the 3 and 4-year old cankers would seem to be
of little importance. The lack of healing in such cases is usually

the result of secondary fungi of the peach canker complex.

Though equipment was not available to establish a series of
studies on the production of sporodochia by cankers covering a com—
plete range of temperature and humidity, an attempt was made to
determine the minimum temperature at which Sporodochia might be

produced in a saturated atmOSphere.

In this study the cankered portions of the twigs were cut out
and placed in water for 7 hours. One group was then held at 4°C

and the other at 7°C. both in a saturated atmOSphere.

Both groups were maintained under the above conditions for 111
hours. By the end of this time there was no visible evidence of
sporodochia in either group. The temperature was then increased to
21°C. After 40 hours at 21°C evidence of sporodochia appeared on
the l-year old canker in the group originally bald at 7°C. but no
sporodochia were ever produced on the 8-year old cankers. Though
these cankers were held longer than 72 hours at 21°C no further

sporodochia] production took place on the inactive cankers. A.max-

 

 

r!

17

imum of 44.4% of the l—year cankers produced conidia. These data are

presented in TABLE III.

TABLE III. Observations of sporodochial production of twig cankers

at 21°C after 111 hours at 7°C.

 

Additional 36 layear cankers 16 2:year cankers 18 3-year cankers
time at 21°C. No. active % active No. active fiactive No. active —% active

 

48 hours 8 22.2% 4 25% o -__

72 . 16 44.4% 4 25% o ' ___

 

In the group held originally at 4°C, but 29.4% of the 1—year can.
kers produced sporodochia. However, 9.7% of the 3—year cankers sporu—

lated after 74 hours at 21°C. These data are presented in TABLE IV.

TABLE IV. Observations of sporodochial production on twig cankers at

21°C after 111 hours at 4°C.

 

.Additional 34 l-year cankers 25 2eyearqcankers 31 3-year cankers
time at 21°C. No. active % active No. active % active No. active % active

 

48 hours 0 --- O --- o -_-
74 a 10 29.4% 6 24% 3 9.7%

 

It is apparent that at temperatures of 7°C and lower, canker—
produced conidia are not significant as a source of spores for the pri-

mary cycles of brown rot.

 

 

 

 

 

‘-

18

FUNGICIDAL CONTROL OF BROWN BOT

IN 1949

As it is practically impossible to destroy all sources of in-
oculum by orchard sanitation practices, and as completely resistant
varieties of peach are not known, the control of brown rot must be
Supplemented by protective Sprays. Thus the major objectives of the
1949 field studies were: (1) the testing of certain Spray materials,
(2) a study of the timing of the fungicidal applications in accordance
with susceptible periods in the development of the host and weather
favorable to the fungus, and (3) observations on the epidemiology of

the disease under Michigan conditions.
Blossom Sprays

Examination of the facts concerning brown rot indicate that con-
siderable emphasis in control of fruit rot should be placed on com-
plete control of blossom blight to eliminate a major source of sec-
ondary inoculum. It is postulated that complete control of blossom
blight over a 2 or 8-year period would automatically tend to eliminate
two sources of inoculum: conidia from currently blighted blossoms
and future conidia from the resultant cankers. With complete control
of blossom blight, the protection of the ripening fruits should be
accomplished readily in light of the reduced spore load. This in turn
would lead to fewer mummies for the over-wintering stages of the fun—

gus, both on the tree and on the ground

We

19

Methods and Materials

The currently recommended program (29) for blossom Sprays in
Michigan is based on studies by Weaver (23) and results of certain
-spray programs of Dunegan (30). The schedule calls for 3 applica-
tions during the interval between the pink and full bloom stages in
those orchards having a recent history of brown rot and if conditions
of humidity are favorable to the develOpment of the fungus. The
timings of the applications are suggested when the blossoms are in

the pink stage of development, 25% Open and 75% open.

Blossom blight varies year to year in severity according to cli—
matic conditions. To be more certain of encountering blossom in-
fection it was desirable to establish eXperiments in locations sub-

ject to different climatic environments.

In the area immediately adjacent to Lake Michigan there are cli-
matic factors differing from those several miles inland. Thus 2
orchards of varied locations were selected in which to set up the ex—
perimental program. One, the Colby Orchard, was situated on the Lake
Shore; the other, the Handy Orchard, was 8 miles inland. In each
orchard a history of both heavy blossom blight and fruit rot is known.
Hold-over cankers were numerous in both situations and 3 to 5 clusters
of apothecia per tree were common on the ground at blossoming time.

In the orchard on the lake shore the mummies had not been removed
from the trees. An attempt had been made to remove them in the Handy

Orchard but the job was far from thorough.

Nine-tree plots (3 X 3) were used for each treatment with all

counts being made on the center tree of each plot. This arrangement

20

allowed for 1 tree on each side of the count tree to act as a buffer
against spray contamination. All Spraying was done from the ground
using a Friend Pecan gun with a No. 10 disc and a pressure of 250
pounds. The Halehaven variety of peach was used in the trials at the

Colby Orchard, and Rochester at the Handy Orchard.

In an attempt to determine the effectiveness of each individual
application in relation to the phenological factors of temperature
and humidity, a factorial design of 4 sprays was planned. It was
heped that the results might indicate more effective timing of sprays
for control of blossom blight and to eliminate unnecessary applica—

tions.

The materials used here in the factorial design were wettable sul-
fur, 5 pounds in 100 gallons, plus a wetting agent (B—l956) and Stanc-
fide, a fungicide manufactured by the Standard Oil Company (Indiana)
at % pint per 100 gallons. In addition to the two fungicides used in
the complete program, a 4-spray treatment of liquid lime sulfur, 2
gallons in 100 plus a wetting agent (B-1956), and L—7752 and L—8299
at i pint in 100 gallons were planned. The latter two numbers desig—

nate code numbers for experimental materials furnished by the Standard

Oil Company (Indiana).

Since Weaver's work (23) has shown the improbability of blossom
infection during the pink stage of bloom unless the stigmas were ex-
posed, the initial spray was planned when approximately 25% of the
blossoms had their stigmas exposed. The other sequences were to be

applied when the blossoms had 50%, 75%, and all their stigmas ex—

21

posed or at about 2g—day intervals during a normal blossoming sea—
son. TABLE V indicates the planned applications. However, the rapid

advancement of the blossoms allowed only 2 applications.

TABLE V. Factorial design of spray applications for blossom blight

control.

 

Halehaven variety -— Colby Orchard

 

 

Plot No. Material Sequence of Applications
1 Stanofide 1 _ - _
2 " 1 - 3 4
3 “ 1 _ _ 4
4 ' 1 2 — _
5 ' l 2 3 4
6 ' l 2 3 _
7 ” l 2 - 4
8 ' - 2 _ _
9 ' - 2 _ 4

10 . ” - 2 3 4
ll ' - 2 . 3 _
12 " - - 3 4
13 " .. .. 3 ..
l4 " — _ _ 4
15 Wettable sulfur + B-1956 . 1 - — -
15 u u u 1 _ 3 4
17 n a u 1 _ _ 4
18 fl " " 1 2 .. ..

l9 " " " 1 2 — 4

L-“

 

. “-y

 

TABLE v (Cont).

22

 

 

 

Plot No. Material Sequence of7Applications
20 Wettable sulfur + B—1956 1 2 3 4
21 ' ' ' l 2 3 -
22 " " " - 2 — 4
23 I I I _ 2 _ -
24 I I I _ 2 3 4
25 I I I _ 2 3 _
26 ' ' ' - - 3 4
27 I I I _ - 3 -
28 I I I _ _ _ 4
29 L~8299 l 2 3 4
3O L—7752 1 2 3 4
31 Non-sprayed - — _ -
32 I i - _ - -

 

 

Rochester variety - - Handy Orchard

 

Plot No. Material
..g======================al
1 ‘ Stanofide
2 I
3 I
4 I
5 I
6 I
7 I
8 I

Sequence of Applications

 

 

- .
I
1
a +
, ll
’4
.—
,.
.-
.
._.
.
.l
.—
.
A.
.-
‘1
--
I
..
.
t
.-
.-
-,. ,. . . .
It I
A
-.......-. _. - a ---e.l~
. §,.‘ .
. _-. . - 1 »- . ..
u... *4 .... .~ . 4.,

r.
c

.
,
‘7
, ..
. 1..
r,-
.4 _.
. .
‘4--.
n
.
.
-_.
_ a
.
1 iv

 

 

..
.4. -
n
i
a 0--
"'1
.‘a

 

23

TABIE V (Cont).

 

 

 

Plot No. Material Sequence of Applications
9 Stanofide — 2 - 4
10 " - 2 3 4
ll " - 2 3 .—
12 " — - 3 4
13 " -. .. 3 ..
14 " — .. .. 4
15 Wettable sulfur in 3-1956 1 — — ..
16 Non-sprayed - .. .. ..
l7 Wetteble sulfur + 3—1956 1 - 3 4
18 " " " 1 - - 4
19 - . I I I 1 2 _ _
20 " " " " l 2 3 4
21 ” " " l 2 - 4
22 " “ " l 2 3 -
23 I I I _ 2 _, 4
24 I I I _ 2 _ _
25 " " " - 2 3 4
26 " " " - 2 3 -
27 " " " - - 3 4
28 I I I _ _ 3 _
39 . . I I I _ _ _ 4
30 Liquid lime sulfur + 3-1956 1 2 3 4
31 L-7752 1 2 3 4
32 L-8299 1 2 3 4

l.
M
.
i
.
4'
V
'1
.

 

TABLE V (Cont).

 

 

 

Plot No. Material Sequence of Applications
33 Non-Sprayed - - - _
34 I n _ _ _ _

 

Coincident with the pink stage of bloom, a period of unseason-
ably warm weather was experienced, including warm nights. As a re—
sult the complete opening of all blossoms occurred in 4 days rather
than the usual average of 10 days. Thus, it was impossible to carry
out the complete program and but 2 of the 4 sequences planned were
applied, these when 25% of the bloom had their stigmas exposed and at

£111]. bloom.

The first application was applied on the Handy plots on April
30. At the time the application started, 25% of the blossoms had
their stigmes exposed. The following day, May 1, 0.4 inch of rain
fell during intermittent showers throughoutthe daylight hours. On
May 2 the first sprays were applied to the plots at the Colby Or-
chard. 284 of the stigmas were eXposed. On May 3 and 4 the second
sequence of applications were given to the Handy and Colby plots
respectively. In both cases the trees were in full bloom. Blossom

blight counts were made 10 days after the last Sprays.
Results of Blossom Blight Studies

One of the most apparent differences in the results obtained is

 

.7 .
.
b 1 w ..
u
. «I. r
O . a. a r
. .
u ., I, - . 9 4
l7 . .a . .
L .
a .
. , .
1 _ , . .
t
7 7 .
.- . .
c
‘
. .
. \ . 1 w
7 7 . -
a x I .
e . r .
I ,
r .
a ‘ I
. ..
. .
. . , 7.
0 u b I
It .
.
a
_ . 1
7 , . .
. .7 . . t
1 a 1
I V I
. .
. O - ,
I.
. I
Q.
, a 7 1 ,
.
J 7
vs
I . .
s A
.
1
. o
. \ .
‘ . t I
I a
. 7 _ a
r
. e
7 1.
I

25

the difference in the amount of blight in the non-Sprayed plots in
the 2 orchards. The average blight in 8000 blossoms counted in the
Colby Orchard was 5.3% while the average in 9000 blossoms in the Handy
Orchard was 1.11%. This could not be attributed to differences in the
amount of inoculum and was probably concerned with differences in rel-

ative humidity at the critical periods of infection.

It is apparent from the results obtained in the Handy Orchard
that the second spray might well have been omitted. The ineffective-
ness of this spray is demonstrated by the fact that the incidence of
of blight in 4000 blossoms each in the Stanofide and wettable sulfur
plots that received 2 applications was not materially below that of
the first spray. This would be anticipated if sprays are protective
only since the first spray was applied the day prior to the rain. It
is apparent from these results that the rain initiated the only in-
fectious period during bloom. With the great amount of apothecia pre-
sent it might well be questioned why more blight did not occur as pre-
cipitated moisture is not necessarily essential for infections of stig—
mas. However, the day following the precipitation the relative humid—
ity dropped below 70% and remained there for several days. It is
possible that this accounts for the little further deve10pment of
blossom blight (23). Too, the combination of the low humidities and
high temperatures during the opening of the blossoms (88 to 92°F) may
have stopped fungus growth and delimited the lesions if infection did
occur. It was not possible to determine if infection other than that
which became visible did occur. Because of the high seasonal tem-
peratures the petals drOpped in a comparatively short time after the

full bloom stage was reached making accurate observations impossible

26

for more than 72 hours after the precipitation.

In the Colby Orchard the rain.had occurred before any sprays
were applied. In these plots the second sequence of Sprays or those
applied during full bloom were the most effective, reducing blossom
blight 89% where Stanofide was used and 87% where wettable sulfur was
applied. It is true that the first application greatly reduced the
incidence of blight, however where both applications were made there
was little decrease in the amount of blight over the one full bloom
spray. Indications are that the infection period occurred after the
second Spray; that the first spray retained its protection for those
28% of the Open blossoms covered and that the second spray alone not
only protected the analogous 28% but also the blossoms which had 0-

pened later.

There were some differences in control of blossom blight among
the different materials used. In both orchards the greatest reduc-
tion of blossom blight was in the plots sprayed with the Standard Oil
Company eXperimental sprays L-7752 and L-8299. In each case however,
the precentage of blight was based on 1000 blossoms rather than on 3
or 4 thousand as were counted in the Stanofide and wettable sulfur
plots, and the significance is questionable. In the Colby Orchard
there was little difference in the fungicidal effectiveness between
Stanofide and wettable sulfur while at the Handy Orchard the sulfur
resulted in somewhat better control. Liquid lime sulfur resulted in
better control than wettable sulfur at the Handy Orchard but the counts
were based on 1000 blossoms in the case of the liquid lime sulfur and

4000 blossoms for the wettable sulfur and the superiority may be ques-

27

tioned. Even though the temperature was 89°F, 2 gallons of liquid
lime sulfur in 100 caused no evident injury to the blossoms or fruit
set. No phytotoxic reactions were noted from any of the materials ap—

plied. TABLES VI, VII, VIII, and IX show these data.

TABLE VI. Blossom blight counts.

 

Halehaven variety - Colby Orchard.

 

 

Plot No. Material Applications Amount of at Blight
Applied Blight /1000 .
Blossoms

 

 

 

 

1 Stanofide 1 - 10 1.0
2 ” l - 12 1.2
3 " l - 11 1.1
4 ” l 2 7 0.7
5 ' 1 2 6 0.6
e " 1 2 '7 O. '7
7 “ 1 2 8 0.8
8 ” - 2 4 0.4
9 ” - 2 5 0.5
10 " — 2 7 0.7
11 ' - 2 8 0.8
12' Used as check None 55 5.5
13 " ” ” 55 5.5
14 A ' " " 53 5.3
15 Wettable sulfur + 1 - 12 1.2
3-1956
16 ' ” 1 - 15 1.5
17 n w 1 _ 15 1.5

TABLE VI (Cont)

28

 

 

 

 

 

 

 

 

 

 

Plot No. Material Applications Amount of % Blight
Applied Bl ight /1000
Blossoms
19 Wettable sulfur 1 2 4 0.4
+ B—1956
20 " " 1 2 5 0.5
21 ” " 1 2 -4 0.4
22 ' " ” - 2 7 0.7
23 " " - 2 7 0.7
24 " “ — 2 6 0.6
‘25 " " - 2 8 o. s
26 Used as check None 55 5.5
2'7 ' " 53 5. 3
28 " " 54 5.4
29 L—8299 1 2 2 0.2
30 L—7752 1 2 0 0.0
31 Non-sprayed 49 4.9
32 ” ” 50 5.0
a: -;:=:;
TABLE VII. A summary of the above table.
Material Applications No. Blossoms % Blight % Reduction
Applied Counted '
Stanofide 1 _ 8000 1.1 79
" - 2 4000 0.6 89
fl 1 2 4000 0.7 87
Wettable sulfur 1 - 8000 1.4 74

29

TABLE VII (Cont)

 

—_

 

 

Material Applications No. Blossoms % Blight % Reduction
Applied Counted
Wettable sulfur - 2 4000 0.7 87
" ” 1 2 4000 0.4 92
L—7752 1 2 1000 0.0 100
L—8299 ~ 1 2 1000 0.2 96
Non-Sprayed 8000 5.3 -

 

 

TABLE VIII. Blossom blight counts.

 

Rochester variety - Handy Orchard

 

 

 

Plot No. Material Applications lmount of 5% Blight
Applied Blight/1000
Blossoms
1 Stanofide 1 - O 0.0
2 s 1 - 2 0.2
3 a 1 - 1 0.1
4 I l 2 1 0.1
5 I 1 2 2 0.2
6 I 1 2 o 0.0
7 I 1 2 o 0.0
a I - 2 3 0.3
9 w — 2 1 0.1
10 I - 2 2 0.2

11 ' - ' 2 0 0.0

30

TABLE VIII (cont)

 

 

 

 

Plot No. Material Applications Amount of % Blight
Applied Blight/1000
Blossoms.
12 Used as check None 1 0.1
13 " ” “ O 0.0
14 ” " “ 0 0.0
15 Wettable sulfur 1 - 1 0.1
+ B-1956
16 Non-Sprayed 2 0.2
17 Wettable sulfur I — 0 0.0
+ 3-1956
18 ' ' 1 - 0 0.0
19 " " 1 2 1 0.1
20 ' ” 1 2 1 0.1
21 ' ” l 2 0 0.0
22 ' ” l 2 O 0.0
23 n u "' 2 2 0.2
24 I. II "' 2 1 00 1
25 I N "' 2 3 O. 3
26 I n " 2 O 0.0
27 Used as check Eons 1 0.1
28 ' " " 0 0.0
29 ' ” “ 2 0.2
30 Liquid 1 ime 1 2 l 0. 1
sulfur + 3-1956
31 . L-7752 1 2 O 0.0
32 L—8299 1 2 0 0.0
33 Non-Sprayed 1 0.1

34 I I . 3 0.3

31

TABLE II. A.summary of the above table.

 

 

 

 

Material Applications No. Blossoms % Blight % Reduction
Applied Counted

Stanofide 1 - 3000 0.75 32.2
I _ 2 4000 1.5 -26.0
I 1 2 4000 0.75 32.4
Wettable sulfur 1 - 3000 0.33 70.3
n I - 2 4000 1.5 -26.0
I I 1 2 4000 O. 5 55. 0
Liquid lime sulfur 1 2 1000 0.1 91.0
L—7752 l 2 1000 0.0 100.0
L—8299 1 2 1000 0.0 100.0

Non—sprayed 9000 1.11

 

”:3
(x)

Post-bloom and Pro—harvest Sprays

Methods and Materials

One of the considerations during the 1949 season's study was the
testing of certain new materials. One of these newer fungicides is
Stanofide, the trade name of a fungicide produced by the Standard Oil
Company of Indiana. Its use thus far has been confined primarily on
apples as a protectant against apple scab. Since this product in—
dicated considerakle control of brown rot in small—scale tests by the
Standard Oil Company workers the previous season, it seemed advisable
toundertake more thorough trials using this fungicide. The Michigan
State College Spray Calender (29) suggests 3 Sprays shortly after
bloom. Any fungicide to be of value during these sprays would need to
be compatable with the insecticides used in controlling the plum cur.
culio and with D. D. T. used in control of the oriental fruit moth,
also the sucking insects responsible for "catfacing'. Therefore, the
post-bloom sprays were designed to test the compatabilities of the
fungicides and certain insecticides as well as comparative control of
diseases by the different combinations. In addition to Stanofide,
L-7752, L-8299, and wettable sulfur were compared as fungicides dur_
ing.these trials. The fungicidal plots were so established that they
would form a continuous fungicidal program from petal fall to harvest
time. Additional fungicides, to be indicated later, were also used

during the pre-harvest Sprays.

The two orchards selected for these trials were different from

those used in the blossom studies so that all plots would have had

at.

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33

identical treatments previous to this phase of the experiments begin-
ning with the petal fall Spray. As before the orchard locations were
varied. Plots of Rochester and Elberta varieties were established on
the Deaner Farms, 8 miles inland from Lake Michigan, and plots of Hale-
haven and Elberta varieties were set up in the Closson Orchard, % mile
from the lake shore. Nine—tree blocks (3 x 3) were used and where

possible all counts and observations were made from the center tree

in each block;

Fungicides were used in combination with insecticides in three
Sprays. These applications were made at petal fall, when 75% of the

Shucks were off, and 2 weeks after the latter (first cover).

The purpose of a fungicide in these sprays is two-fold: control
of brown rot and control of peach scab. Very little data is avail-
'able to show the actual value of a fungicide at this time for brown
rot control. The young fruits are seldom seen rotting unless a
~wound has occurred. It is possible during prolonged periods of wet
weather for the fungus to penetrate a young fruit from a diseased
calyx. However, weather conditions are seldom encountered where such

infections occur, and it is doubtful that the fungicide would be of

value in such a case.

TABLE 1 records the various insecticide—fungicide combinations
used in the above sprays. The amounts of the various materials used
in this series of sprays and in the pro-harvest Sprays per 100 gal-

lons of solution is indicated in TABLE XI.

34

D. D. T. was included in the shuck fall and first cover Sprays
at the Closson Orchard, but none was used at the Deaner Farms at the

request of the owner.

No effort was made to accurately determine the effectiveness of
the various insecticide-fungicide combinations in regards to control
of insect pests, so the study was concerned solely with the injury

phase.

TABLE I

35

Post-bloom sprays.

 

Rochester variety -- Deaner Farms

 

 

 

 

 

 

 

 

Plot No. Fungicide Insecticide
4 Stanofide Basic lead
5 Stanofide BHC
6 Stanofide Chlordane
7 Stanofide Acid lead plus corrective
8 None None
9 Stanofide Acid lead
13 None Acid lead plus corrective
14a wettable sulfur plus 3-1956 Chlordane
15 wettable sulfur plus B—l956 Chlordane
16 Wettable sulfur plus 3-1956 Acid lead plus corrective
17 Wettable sulfur plus B-1956 Chlordane
18 Stanofide None
===at: l=================:__
Elberta variety —— Deaner Farms
Plot No. Fungicide Insecticide
1a,b,c None Chlordane
2 None Chlordane
3 Stanofide Parathion
4 Stanofide Basic lead
10a Arathane Arathane
10b None None
11 L-8299 See page "39"

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TABLE X (Cont)

 

 

m

 

Plot No. Fungicide Insecticide
1......m...‘ 22:: —: ‘hw “‘ ~-~-——-———-—-—-—
12 Ip7752 See page “39"
13 None Acid lead. plus corrective

 

-._‘.- §

Halehaven variety -- Closson Orchard

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Plot No. Fungicide Insecticide
1 Stanofide Acid lead plus correvtice
2 Stanofide Chlordane
3 Stanofide BHC
4 Stanofide Basic lead
5 Stanofide None
6 None Acid lead plus corrective
7 Stanofide Parathion
11 Wettable sulfur plus Chlordane
B-l956
13 L-7752 See page " 39"
15 None None
Elberta variety -- Closson Orchard
Plot No. Fungicide Insecticide
m— -—'4==“" " *2..-
2 Stanofide Chlordane
6 None Acid lead plus corrective

7 Stanofide

Parathion

TABLE X (Cont)

 

 

 

Plot No. Fungicide Insecticide
8 Wettable sulfur plus Chlordane

3-1956

9 wettable sulfur plus Acid lead plus corrective
3-1956

10 Wettable sulfur plus Chlordane
3-1956

ll Wettable sulfur plus Chlordane
3-1956

12 None None

13 L-7752 See page "39"

14 L—8299 See page '39"

 

h

TABLE XI. .Amounts of materials used in the post-bloom and pre-

harvest sprays per 100 gallons.

 

Fungicides

.Amount per 100 gallon

 

m _==;=

 

 

 

 

Acti-dione

Arathane

03.305 (thm and Haas eXperimental)

Liquid lime sulfur

L—7752 (Standard Oil (1nd.) experimental)

L-8299 (Standard Oil (1nd.) exPerimental)

Stanofide
Wettable sulfur

Wetting agent (3-1956)

 

20, 10, 5, and 2 ppm

~3/4 lb

1% 1b
3 qts
% pt
% pt
a pt
5 lbs
1% 02

.* C-..-~*--~‘. II.“
S...“

TABLE XI (Cont)

 

 

 

Insecticides Amount per 100 gallons
Acid lead 2 lbs
Arathane 3/4 lbs
Basic lead 3 lbs
BHC 3 lbs
Chlordane 2 lbs
Corrective: Zinc sulphate (flake) 4 lbs
spray lime 4 lbs
D. D. r. (50%) 1% lbs
Parathion (15-73) 1% lbs

 

 

 

 

.-.-

 

 

Spray Injury

There was no evidence to suspect incompatability or detrimental
results following the use of Stanofide mixed with Parathion, BBC, and
Chlordane, with or without D. D. T. added. All tank mixes were ob-
tained without difficulty. Experience indicated, however, that the
Stanofide be added to the tank when the latter is nearly full. This
tends to prevent excessive foaming which may occur if the fungicide

is added to a partially-filled tank.

Some difficulty was eXperienced in mixing certain insecticides
in combination with the fungicides L—7752 and L-8299. The insecti—
cides tried in combination with these two fungicides were Chlordane,
BBC, and Parathion and D. D. T. alone and in combination with the
other 3 insecticides. A good mix was finally obtained by adding the
fungicide to the tank as soon as the agitators were covered and in
Operation. The insecticide was sifted into the tank as it neared the
full point. This resulted in considerable foaming but not so much so
as to impair the activity of the pump. As several combinations of
insecticide-fungicides were used on each plot of L—7752 and L—8299,
no insecticide is indicated in the TABLES following these two fungi—

cides.

Severe injury resulted whenever lead arsenate was used as the in—
secticide. Typical arsenical injury on foliage occurred where acid
lead plus a corrective of zinc sulphate and lime (2—4—4) was used
without a fungicide. The injury was not enhanced by adding wettable

sulfur to the insecticide. There was, however, somewhat more arsenic-

Cal injury when Stanofide was added to the acid lead plus the corrective.
Stanofide and basic lead caused injury in the approximate severity as
with acid lead and a corrective used alone or in combination with wet-
table sulfur. The combination of acid load without a corrective and

Stanofide caused 50% defoliation following one application.

The result of these fungicide-insecticide combinations indicate
that Stanofide has no corrective action for lead arsenatc and the com—

bination should not be used on peaches.

41

Pre-harvest Spray Trials
Methods and Materials

Most of the plots set up in the post—bloom Sprays were continued
using the same fungicide throughout the pre-harvest applications.
Additional plots of Acti-dione (an anti—biotic chemical, cyclohexi-
mide, produced by the Upjohn Company) and CR-305 (Rohm and Haas ex-
perimental fungicide) were applied during the pre—harvest sprays only.
Plots on which these materials were used had received 3 applications
of an insecticide (Chlordane), during the three post-bloom sprays.

D. D. T. was added to all fungicide plots in the first two pro-har—

vest sprays.

Applications of fungicidal Sprays were started one month before
harvest taking into consideration the estimated picking dates of the
varieties and their locations. 4 applications were made at approx-
imately lO-day intervals, the last one applied the day previous to

picking.

All peaches were harvested at the firm-ripe stage of maturity.
A two-bushel sample was picked from each plot. One bushel was placed
in cold storage (34°F) for 48 hours and then removed to common stor—
age for 4 additional days. The other bushel was placed in common
storage for 6 days. At the end of the 6 days each sample was exam-

ined to determine the extent of the infection incurred.

42
Discussion of Results

In the trials on the Rochester variety of peach, the wettable
sulfur and liquid lime sulfur gave the best control of brown rot: 88
and 97% respectively under conditions of 2 days cold - 4 days common
storage. Only with the Chlordane combination (Plot 6) did Stanofide
compare with the above two fungicides giving 88% control under the

same storage procedure.

Under conditions of continuous common storage, the advantage of
wettable sulfur over Stanofide was indicated. However, liquid lime

sulfur was not superior to Stanofide in this type storage.

On the Halehaven variety under conditions of 2 days cold - 4
days common storage, liquid lime sulfur gave the best results with 94%
control. Stanofide was slightly superior in continuous common storage.

Under the latter conditions, L—7752 gave but 49% control.

On Elberta variety several fungicides gave 100% control under
conditions of little brown rot even on the non-sprayed plots. These
materials included wettable sulfur, liquid lime sulfur, Acti-dione at
5 ppm, and Arathane. Stanofide with basic lead as the insecticide, a
combination not recommended because of foliage injury, also gave 100%
control. In all the above tests, the peaches were subjected to 2 days
cold - 4 days common storage. The grower program of a liquid lime suL
fur (2 quarts in 100 gallons) and 3 sulfur dusts, and CR—SO5 were not

satisfactory. These data in TABLES XII, XIII, XIV, and.XV.

Rochester Variety

 

 

 

Insecticide No.
(applied in 3 post- fruit
Plot No. Fungicide bloom Sprays only) counted
4 Stanofide Basic lead ‘ 152
5 Stanofide BHC 230
6 Stanofide Chlordane 197
7 Stanofide Acid lead plus
corrective 186
8 Non—Sprayed Non-sprayed 195
9"I Stanofide Acid lead 142
l4-a** Wettable sulfur“
plus 3—1956
b** Liquid lime sul- Chlordane 157
fur plus 3-1956
15 Wettable sulfur
plus 3-1956 Chlordane 188
16 Wettable sulfur ,Acid lead plus
plus 3—1956 corrective 209
17-a** Wettable sulfur
plus 3-1956 Chlordane 213
b"”‘l Stanofide
18 Stanofide None 201

* 1 post-bloom spray at petal-fall; 4 pre—harvest applications

Of Stanofide.

** a-Spray program for the 3 post-bloom sprays.

b-Spray program for the 4 pre-harvest sprays.

 

44

Deaner Farms

 

 

% rot No. % rot % rot reduction
cold fruit common cold common
storage counted storage storage storage
-:
86 No sample -- 60 -..
19 239 26 79 73
11 286 38 88 67
41 173 45 53 54
89 190 97 —-- _--
59 No sample --- 33 --_
11 144 55 88 43
3 198 17 97 82
3 198 8 97 92
17 189 32 80 67
43 174 69 52 29

—..._.-

 

 

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Halehaven variety

 

 

Insecticide No.
(applied in 8 post- fruit
Plot No. Fungicide bloom Sprays only) counted
1 Stanofide Acid lead plus
corrective 172
3 Stanofide Chlordane 196
3 Stanofide BHC 192
4 Stanofide Basic lead ———
5 Stanofide None 184
6 None Acid lead plus
corrective 205
7 Stanofide Parathion 166
ll-a*** Wettable sulfur
plus 3-1956
b*** Liquid lime sul- Chlordane 196
fur plus 3-1956

13 L—7752**** See page "39" 229

‘ Percent reduction based on rot in Plot 6.

** Many, small, necrotic areas were just beginning to appear
but these were not counted due to the inability to identify
them as brown rot.

##t a Spray program for the 3 post-bloom sprays.

b Spray program for the 4 pre—harvest sprays.

**** Fruit heavily infected with bacterial spot.

% rot
cold
storage

7“

17

Closson Orchards

46

 

 

 

No. % rot % rot reduction*

fruit common cold common

counted storage storage storage
166 11 71 81
232 6 82 90
148 4 82 93
218 6 _—_ 90
165 52 59 10
187 58 —-- --_
224 9 88 81
154 7 94 89
194 29 76 49

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“313 XIV.

FRUIT HOT

Elberta variety_

 

 

Insecticide No.
(applied in 3 post- fruit
Plot No. Fungicide bloom Sprays only) counted
2 Stanofide Chlordane ---
6 None Acid lead plus
corrective 145
7 Stanofide Parathion 85
8—a""'l Wettable sulfur
plus 3-1956 Chlordane 123
b** Stanofide
lO Wettable sulfur
plus 3—1956 Chlordane 176
ll-a"”'I Wettable sulfur-
plus 3—1956
b** Liquid lime sul— Chlordane 172
fur plus 3—1956
12 Non-Sprayed Non-Sprayed 152
13 L-77SE*** See page "39" 105
14 L-8299 See page "39" 128
up

**

*t*

more rot present than in the non—Sprayed plot.
a Spray program for the 3 post-bloom sprays.
b Spray program for the 4 pre—harvest Sprays.

Fruit heavily infected with bacterial spot.

 

 

 

48

Closson Orchards

 

 

% rot No. % rot % rot reduction
cold fruit common cold common
storage counted storage storage storage
12 135 37 (~33)* (-34)*
4 86 15 5O 46
2 114 12 75 56
O 169 10 100 64
O 173 12 100 57
8 147 28 --— _-_
2 128 25 75 ll
3 124 16 65 45

TABLE xv.

' ' o .
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u ' ,

-

FRUIT BOT

Elberta variety

 

 

Insecticide No.
(applied in 3 post- fruit
Plot No. Fungicide bloom sprays only) counted
15a*
bl!
c* None Chlordane
e"I Acti-dione (lOppm) 91
1" Act i-dione (5ppm) 113
g‘ Acti—dione (2ppm) 97
2—a** None H -
b** CR 305 Chlordane 104
3 Stanofide Parathion 97
4 Stanofide ‘ Basic lead 97
lO—a Arathane Arathane 76
b Non-sprayed Non-Sprayed 56

ll L—8299 See page "39" 96

12 L—7752 See page "89“ 102

13 None Acid lead plus

corrective _-_

Grower program*** 68
’ 1 a,b,c Spray program for the 8 post-bloom sprays.
l e,f,g Spray program for the 4 pre-harvest sprays.
*‘ 2 a Spray program for the 3 post-bloom sprays.
2 b Spray program for the 4 pre-harvest sprays.

**‘ Grower program: 3 post-bloom sprays of EKG and sulfur paste.
Pre-harvest applications: (1) 2 qts liquid lime
sulfur, (2) sulfur dust, (3 and 4) sulfur dust
by plane.

eeem

More rot than in non—Sprayed plot.

 

50

Deaner Farms

 

% rot No. % rot % rot reduction
cold fruit common cold common
storage counted storage storage ' storage
1 100 23 86 36
0 ---- ---- 100 —-- -
2 -—-- --- 71 ----
3 96 36 57 3
1 114 20 86 44
0 114 16 100 56
0 ---- ---- 100 ----
7 75 36 -—-— --_-
1 100 16 86 56
1 100 18 86 50
__-_ 100 30 -—-- l7
3 64 42 57 (-14)#¢*t

r
~ — _-
— c..-

v .

”wt-cu-

 

 

A.severe phytotoxic reaction on the foliage occurred where
L—7752 was used as the fungicide in the pre-harvest sprays. The in-
Jury was characterized by large, irregular, necrotic areas on the
leaf which soon dropped out. Where the necrotic areas were numer—
ous the leaf tack on a very ragged appearance after the lesions had
fallen. The injury was not noted on the plots after receiving the
3 post-bloom sprays, but it was common on both Halehaven and Elberta
varieties during the pro-harvest sprays. A.slight streaking of the
color on the fruit was noted about 3 weeks prior to harvest. Howe

ever, this had largely disappeared at picking time.

In all Stanofide plots on the Rochester variety, a slight scat-
tering of small, shot-holes was seen after the first pre~harvest
spray was applied. This reaction was not observed on Halehaven or
Elberta varieties at any time nor was it observed on Rochester fol-
lowing the later sprays. Attempts to duplicate the injury on other

Rochester trees failed.

Acti-dione caused severe cracking of firmrripe Halehaven peaches
and to a lesser extent Elbertas. The cracks, often % inch deep and
varying from 2 to 8 in number per peach, radiated in several direc-
tions. In addition, the spray mottled the fruit, seeming to actual—

1y dissolve the red coloring of the skin.

A.slight amount of sulfur burn on the foliage was noted on those
trees receiving liquid lime sulfur (3 quarts in 100). This was most

evident on the suckers and terminal leaves of the twigs.

l ..
r-
v
1
.k
t
v
C

 

52

At harvest time there was no apparent differences in the stage of
maturity in respect to the different treatments. Stanofide, L—7752,
and L—8299—sprayed fruit showed slightly brighter color because of the
absence of apparent residue than did the fruit sprayed with liquid

lime sulfur, wettable sulfur, CR—SOS, and Arathane.

53

Fungicidal Applications Under Conditions of Heavy

Inoculum

Hear harvest time an orchard of Halehaven peaches with a high
incidence of infection came to our attention. It had received only
a haphassard spray program.after the blossom sprays because of the
prospects of a small crop. Counts of the fruit on 3 random trees re-
vealed ll.4% rotted fruit hanging in the trees at this time. Compar-
ative sprays of fungicides mixed with 100 gallons of water, namely:
wettable sulfur (5 lbs) plus 3-1956, Stanofide (g pt), end Acti-dione
(20ppm), were applied the same day the grower applied a spray of liq.
uid lime sulfur (2 pts) plus 3-1956 to the remainder of the orchard.
Two days later a picking was made. 2—bushel samples were harvested
from each treatment and placed in cold storage for 2 days and then re-

moved to common storage for 3 days.

2 days after the first picking another application of the same
materials was made and compared with another grower-applied liquid
ilime sulfur spray. No second application of Acti-dione was made be-
cause of the severe cracking of the fruit. After picking, the fruit
was subjected to the same storage procedure as after the first appli-

cation.

The control effected by Stanofide and wettable sulfur was supe-
rior to that obtained by the grower using liquid lime sulfur while
Acti-dione under these conditions showed a high rot count. The high
rot count for Acti-dione might have resulted from the fruit cracking

attributed to that material. TABLE XVI shows the percentage of brown

 

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rot following the different treatments.

TABLE XVI. Fruit rot under conditions of heavy inoculum.

 

 

 

 

lst application 2nd application.

No. fruit No. fruit ‘—
Material counted % rot counted g rot
Stanof ids 309 71 349 55
Wettable sulfur 236 67 210 45
plus 3-1956
Acti-dione (zoppm) 283 84 111* 92
Liquid lime sulfur
plus 3-1956 (grower
applied) 134 89 238 79

s Only 1 application put on because of the severe cracking of the

fruit due to the chemical.
Dipping Tests

Most of the loss from fruit rot caused by the brown rot fungus
occurs in storage or in transit between the grower and the consumer.
Infection during this stage apparently is due to conidia lodged on
the fruit at picking time and germinating later, or corfidia that have
germinated Just prior to harvest. In an attempt to prevent rot by
killing the surface-borne spores or perhaps retarding germination and
infection of the fruit with a coating of fungus—inhibiting chemicals,

a series of dipping tests were tried.

Methods and Materials

25-gallon mixes of various chemicals were made up in a lOO-gal-

lon drum. The peaches to be dipped were put in Open field boxes and
placed in the solution. They were immersed for approximately 30 sec-
ends and the solution washed thru them by raising and lowering the con-
tainer. 2-bushel samples were used for each treatment. After draining

for 1% hours they were placed in common storage for 5 days.

The peaches in this test were the Rochester variety. The samples
were picked out of a grower-load and hand-sorted for bad and over-ripe
fruit. These peaches had previously received a complete spray prod
gram of blossom, post-bloom, and pro-harvest sprays, both fungicides

and insecticides.

The samples were from two different parts of the farm and are
designated as the Lower and Upper Orchards. They received an iden-
tical spray schedule throughout the season, applications being made
on the same day. However, certain horticultural practices differed.
The Lower Orchard was heavily fertilized promoting lush growth that
cut down air circulation allowing longer periods of wet fruit and
interferred with spray penetration into the tree. The Lower Or-
chard had not been pruned during the previous dormant season as had
the Upper Orchard. A.good deal more rotted fruit was hanging in the
trees at harvest time in the Lower Orchard. These factors account
for, at least in part, the difference in the percentage of rotted

fruit in the nonédipped samples after 5 days in storage.

None of the materials used in the dipping tests materially re-
duced the incidence of brown rot. Liquid lime sulfur was the most

effective reducing the rot l4 and 15%. In many instances the dipping

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56

 

 

 

 

 

 

resulted in more rot than developed in the non—dipped samples. These
data are presented in TABLE XVII.
TABLE XVII. Dipping trials.
Lower Orchard
No. fruit % 5 Reduction
Material ' counted Bot over non-dipped
r WM
Not dipped 280 94 . —..
Water 258 97 {-3)
lettable sulfur (5 lbs) 292 86 9
lettable sulfur (5 lbs) plus
3-1956 296 88 6
Liquid lime sulfur (3 qts) 272 81 14
Liquid lime sulfur (3 qts)
plus 3-1956 286 80 15
Acti-dione (appm) 285 95 (-1)
Acti—dione (5ppm) 310 84 11
Acti-dione (loppm) 279 95 (-1)
Acti—dione (BOppm) 292 90 4
Stanofide (i-pt) 253 99 (-5)
3-1955 (2 oz) 250 99 (-5)
Fermate (1% lbs) plus 5—1958 292 95 (-2)
Dithane (D—l4, 1 qt) 262 97 (—3)

.Arathane (% lbs) 119 95

(~2)

 

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TABLE XVII (Cont)

57

 

Upper Orchard

 

 

 

 

 

 

No. fruit % % Reduction

Material counted Rot over non-dipped
w ..
Not dipped ‘ 488 18 -__
water 411 78 {—89)
L—7752 (% pt) 411 47 (~66)
L-8299 (§ pt) 417 51 (~69)
Sodium hypochlorite

(280 cc of 5.25%) 454 47 (-66)
Craig 341 B (2% lbs) 388 58 (—71)
Craig 541 c (1 pt) 410 37 (—57)
on 505 (1% lbs) 288 54 (—70)

ll

58

OBSERVATIONS

The following notes are observations on the epidemiology of

brown rot made during the 1949 season by the author.

A plentiful number of apothecia was observed in many orchards.
It was commonplace to find 6 or 8 clusters of apothecia under a tree.
In one instance 28 clusters were counted under a single tree. The
majority of these apothecia were mature during the time peaches were
in bloom. Yet the average blossom blight in several orchards where
many apothecia were present was less than 1%. In one case, 5.3%

blight was counted on non-sprayed trees.

Usually mmmmies require at least partial burial before apothecia
are produced. It was noted, however, that in some orchards where a
heavy cover crop existed creating a local atmosphere of high moisture
content, apothecia were coming from mummies on the surface of the soil.
In all cases the stfipes came from the underside of the mummy where it

was in contact with the soil moisture.

No cankers except the ones formed as a result of blossom blight
during the current season were observed to sporulate in the field

during observations conducted frounuarch to September.

.An important fact must be kept in mind in attempts to control
brown rot. And that fact is this: all possible sources of inoculum
must be eliminated. For instance, in 1949 the importance of the pre-

sent season's blossom blight and previous season's cankers as a source

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59

of secondary Spores was negligible. Yet fruit rot was serious in
certain orchards, as much as 11% counted on the tree at picking time
and up to 90% after 5 days in common storage. The inoculum for this
\rot must come from somewhere and the fact that there were occasional
mummies left hanging in the trees indicated that they were important
in continuing the epidemic. The writer observed these mummies cling-
ing to the tree throughout the summer. In addition, these mummies
were observed to produce conidia all season with each rain sufficient

to soak the sclerotial membrane.

Another source of secondary spores was important on Red Haven
and Oriole varieties during the 1949 season. These two varieties -
deve18ped a considerable number of split pits when they were about
half-grown. As development of these peaches continued an Opening
occurred at the stem end. In many of these peaches rot was iniated
on the inside and soon enveloped the entire peach. This provided at

tremendous amount of inoculmm for the near-ripe fruit on the tree.

60

CONCLUSIONS

Laboratory studies were undertaken to determine the possibility
of conidial production from over—wintered cankers. After an initial
9 hours wetting, 25% of the l-year cankers were producing conidia
within 7 hours in.a saturated atmosphere. At the end of 24 hours 75%
were active. Prolonged periods in a saturated atmos;here did not ine
crease the number found sporulating. 69% of the 2-year cankers were
active after 24 hours. Indications were that the 3 and 4—year can—
kers are of little importance as a source of conidia for the primary
cycles of peach brown rot. No sporodochia were produced at tempera»
tures of 4 or 7°C after 111 hours in a saturated atmosphere. TABLES

II and IIIe

Blossom blight control experiments showed the importance of a
protective spray on the exposed blossoms Just prior to a rain. TABLE-
II. Wettable sulfur was superior to Stanofide as a fungicide during
the blossom sprays with the 8 experimental spray materials of the
Standard Oil Company showing promise. Controls of 70 to 100% were

obtained.

In compatability tests, Stanofide showed no corrective action
for lead arsenate, basic or acid. The combination should not be used
on peaches. The eXperimental fungicides L—7752 and L—8299 mixed with

difficulty with Chlordane, BHC, Parathion, and D. D. T.

Wettable sulfur and liquid lime sulfur gave the best control of

brown rot on fruit in the pre—harvest sprays where the incidence of

’81'

rot was high. Arathane and L-8299 gave promise. TABLES XIII to XVI.

L-7752 injured foliage during the pre—harvest sprays and Acti-

dione severely cracked firm-ripe fruit.

In dipping no material tested significantly reduced the inci-

dence of brown rot infection in harvested peaches.

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

Bibliography

Amos,.A. The temperature relations of some fungi causing stor-
age rots. PhytOpath. 5:11-19. 1915.

Arthur, J. C. Rotting of cherries and plums, QiiiEE £5392.
igggg S. and X. New York.Agr. Exp. Sta. Ann. Rpt. 4:280-
285. 1886.

Bares, H. P. Brown.Rot and related diseases of stone fruits in
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Bartram, R. R. A.study of the brown rot fungus in northern
Vermont. Phytopath. 6:71-78. 1916.

Berkeley, G. H. Brown rot. Canadian Dept..Agr. Div. Bot. Do-
minion Rpt. 1926:64-65. 1926.

Cation, D., and Dunegan, J. C. The over-wintering of £939-
linia igucticola in twig cankers under Michigan conditions
P1. Dis. Rptr. 33:97-98. 1949.

Cation, D. Unpublished notes gathered in 1946, 1947, and 1948.

Chester, F. D. The rot of peach and other stone fruits.
Peninsula Hort. Soc. (Delaware) Trans. 6:57-64. 1893.

006k, M. T. The blossom blight of peach. PhytOpath. 11:290-
294. 1921.

Curtis, E. M. The morphological aspect of resistance to brown
rot in stone fruit. .Ann. Bot. (Londorfl. 42:39-68. 1928.

Ezekiel, l. N. Fruit-rotting Sclerotinias. II. The.American
brown rot fungi. Md..Agr. Exp, Sta. Bul. 271:87-142.

1924

Fruit-rotting Sclerotinias, III. Longevity of

 

buried brown rot mummies. Md. Agr. Exp. Sta. Bul. 284.

 

‘1 o \
. w
a .
I-.. r
O.
I
‘
I.

e
. .
r.. . I
.
O . i.
I
7.. \ '
Q
.. I
o. x
e u c.
O
.
.
I
. u a
_ 1
.1. .a
.— .n
.-
I
C
X
‘1 _
\ .

‘ \ {l
I . I.
n . .1
.. .
. .
.
.
u I. c _.
.
e I. 1.
. .. .
e ..
I.
C ,
i
a .
C
_
. .
.. . #1
e . .
a
U

 

\

v.

 

FE
r ..
.. .
r
. m r. a a
.
.. .(1 .1.
u
a\ . . ._
. .
. L
J . .8
.. .
,p
. . 1
O
.
1 v
u
1 _ Q

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Hildebrand, E. M. Peach cankers and their control. Cornell
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Honey, E. E. The monilioid Species of Sclerotinia. Mycologia.
20:125-157. 1928.

Jehle, R. A. The brown rot canker of peach. Phytopath. 3:105-
110. 1913.

Peach cankers and their treatment. Cornell Agr.

 

Exp. Sta. Cir. 26. 1914.
McClintock, J. A. Peach disease control. Ga. Agr. Exp. Sta.
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The brown rot situation in 1929. .Am. Fr.

 

Growers Mag. 50:11, 30. 1930.

Mix,.A. J. Brown rot, leaf and twig blight, following peach
leaf curl. Phytopath. 20:265-266. 1930.

Roberts, J. W., and Dunegan, J. C. Blossom blight of peach.
PhytOpath. 16:217—222. 1926. I

Peach brown rot. U.S. Dept. Agr.

 

Tech. Bul. 328. 1932.

Smith, E. E. Peach rot and peach blight. Jour. Mycol. 5:131.
1889.

Weaver, L. 0. Effect of temperature and relative humidity on
the occurrence of blossom blight of stone fruit. Thesis
(unpublished) Cornell U. 1943.

Whetzel, H. R. Unpublished notes. Cornell U. 1935.

Willison, R. S. Peach canker investigations. I. Sci..Agr.
14:39. 1933.

Peach canker investigations. II. Canadian Jour.

 

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woronin, M. Uber Sclerotinia Cinirea and.§. fructigena.

 

Mem..Acad. Sci. St. Peterbourgh. Phys. - Math. 10:1-38.
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Mitchell, A. E., Hutson, R., and Cation, D. The spraying cal-
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Dunegan, J. C., and Goldsworthy, M. C. The control of blossom
blight and its relation to brown rot of Red Bird peaches

at harvest. P1. Dis. Rptr. 32: 4: 136-137. 1948.

 

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