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Control of Sooty Blotch and Flyspeck with a Pre-bloom Application of Captafol

SUMMARY Sooty blotch and flyspeck diseases occurred on apples that developed from hand pollinated blossoms covered with plastic bags in 1974. Trace amounts of the diseases developed on apples sprayed with captafol at delayed dormant, pre-pink, and petal fall stages of development in 1975, whereas unsprayed apples covered at the same time developed twice as much sooty blotch and three times as much flyspeck. With applications of captafol at pre-pink and near full-bloom in 1976, sooty blotch and flyspeck ratings were less than 2. During 1978, when captafol was applied at green tip and metiram was used throughout the cover sprays, sooty blotch and flyspeck incidence was 1.01 and 0.16, respectively.

COVER PHOTO.

Red Delicious apple infected with sooty blotch and flyspeck

(right) and clean apple (left). Solid greenish-black blotches are typical of sooty blotch disease and pin point spots are typical of flyspeck disease.

Information contained in this publication is available to all persons

regardless of race, color, or national origin.

FIRST PRINTING 4M-MARCH 1980

Control of Sooty Blotch and Flyspeck of Apples with a Pre-bloom Application of Captafol
A. J. LATHAM AND M. H. HOLLINGSWORTH1

BLOTCH AND FLYSPECK are problem diseases on apples grown in humid areas such as Alabama. Symptoms of these diseases have been found on July Red Delicious and Transparent apples as early as mid-June (1). Besides causing an unappealing fruit appearance, a high incidence of these diseases has caused apples to fall 3 weeks earlier than disease-free fruit on adjacent trees of Richared Red Delicious apples (9). Sooty blotch is caused by Gloeodes pomigena (Schw.) Colby and flyspeck is caused by Zygophiala jamaicensis Mason. Ascospores of Z. jamaicensis were discharged in April in coastal California during and following the apple blossom season (4). In Indiana, mature ascospores of Z. jamaicensis were found during the first part of June (1), and those of G. pomigena in late May and early June (2). First infections by these fungi occurred before June 21 (6) or within a month of petal fall (8) in Pennsylvania. The spores are airborne for considerable distance, and initiate primary infections on newly developed plant parts (3). Five to 15 days are required for symptoms to develop on apples under cool, moist conditions (6,14). Growth of Z. jamaicensis occurred over a temperature range of 40-80°F (1). Similar moisture and temperature condilions are required for infection by G. pomigena, which explains the association of these fungi (13). Generally, recommended spray schedules in apple-growing areas call for fungicide control of sooty blotch and flyspeck to start with
1Associate Professor, Department of Botany, Plant Pathology, and Microbiology,

SOOTY

and Superintendent, North Alabama Horticulture Substation, respectively.

A

,

Appearance of this apple with its many pin point spots is typical of fruit infected with sooty blotch disease.

the second (11,12) to fourth (7,13) cov er spray, and continue un til harx est. Timing fungicide applications according to such schedules does not appear to coincide 'a ith development of the diseases in Alabama. Both fungi are activ e during humid, cool spring weather, but may be entirely albsent during hot, dry, sum iner weather (2). In Alabama, control of sooty blotch and flyspeck was poor with a dodiiie + ferlbani Ilossom spr ay followed by folpet cover sprays, or a season long aplplication of metiram, mancozeb + dinocap, thiram + folpet, dithianon, or with thiophanate methyl (9).

The purpose of this investigation was to obtain effective control of sooty blotch and flyspeck on apples by improving the tining of fungicidal appjlications in Alabama.

MATERIALS AND METHODS
In 197 1, the seasonal development of sooty blotclh and flyspeck was investigated on imature Richared Red l)elicious apples at the North labanma llorticutilture Substation, Cullman. A 1-quart plastic bag was placed over apple blossolls or fruit clusters, with only a few attached leaves included, and tied to tihe twig. Tile lbag was cut i inch deep) at righlt angles to te bottom, to release wvater condlensate. On \April 9, 15, and 23, a total of 260 blossoms was b~agged on each of six trees. Tile Ilossoms had browned stamens and pistils, indicating pollination polobably had occuired. Bagging continued on April 30 and Mlay 7, with 60 ap~ple clusters

bagged on each of six trees; average diameter of the apples on the two dates was 3/ and 5/ inch, respectively. Fruit set occurred between April 9 and 15. On August 15, all bagged apples and nonbagged check fruit were harvested for disease determinations. Incidence of sooty blotch and flyspeck on each apple was rated on a 0 to 5 scale, where 0 = no disease, 1 = trace, 2 = 2-10 percent, 3 = 11-25 percent, 4 = 25-50 percent, 5 = 51 to 100 percent of fruit surface diseased. In 1975 benomyl 2 (0.5 pound per 100 gallons of water plus 1 quart non-phytotoxic oil) and captafol 3 (5 quarts per 100 gallons plus 1 quart non-phytotoxic oil) were applied at silver tip (March 26), tight cluster (April 11), and petal fall (May 1) stages of growth on Red Delicious apples. The fungicides were applied separately by hand gun as dilute sprays to run-off, using a John Bean sprayer at 400 p.s.i. to six single-tree replicates. Six unsprayed trees served as checks. No oil was used with captafol on April 11 or May 1. On May 9, all trees were sprayed with Guthion 50W and Cygon 267 EC for insect control. No other sprays were applied during the season. Subsequently, Golden Delicious apple pollen (Antles' Pollen Supplies, Wenatchee, Wash.) was applied to stigmas of blossoms on sprayed and unsprayed trees with a camel hair brush and the blossoms were covered with plastic bags. On April 15, 17, and 21, twenty-five hand pollinated blossoms or clusters of blossoms were bagged per tree. Similarly, on April 24, May 1, and May 8, twenty-five developing apples or apple clusters that were naturally pollinated were bagged per tree. The average diameter of 60 apples from six trees was 7/ inch on May 8. On August 5, all bagged and 25 nonbagged fruit per tree were harvested and disease evaluations made. In 1976, captafol (5 quarts per 100 gallons water plus 1 quart non-phytotoxic oil) was applied to 12 trees in the pink stage (April 1) and near full bloom (April 7). Six trees received no additional fungicide applications; the other six were sprayed with metiram4 (2 pounds per 100 gallons water). Fungicide and insecticide applications were made on April 19 and 26, May 3, 10, 17, and 24, June 1, 8, 16, 21, and 29, and July 6, 17, and 30. Six trees were left unsprayed to serve as controls. Apples were harvested on August 8 and disease evaluations were made from 1 bushel of apples randomly selected from each tree.
2Benlate 50WP. aDifolatan 4F. 4Polyram 80WP.

[5]

During 1978, captafol (1976 rate) was applied in the green tip stage (April 3) and, subsequently, metiram (to five trees) was applied at 1976 rates on April 17 and 24, May 2, 9, 19, and 28, June 9 and 23, July 7 and 21, and August 4 and 18. Dodine 5 (0.5 pound per 100 gallons water) was applied during bloom (April 10), followed by metiram cover sprays. Five trees were left unsprayed to serve as controls; however, fruit had rotted or dropped from two of these trees by harvest on August 29. One bushel of apples randomly selected from each tree was evaluated for diseases. RESULTS Observations in 1974 indicated that the source of infection by the sooty blotch fungus might have been inoculum on twigs or leaves within the bags. Sooty blotch was most prominent in the stem depression of the fruit. Other sites of extensive infection were the blossom ends and areas adjacent to where leaves were in contact with the fruit. Sooty blotch developed where plastic bags were in contact with an apple, if the area was wet. Parts of apples submerged in condensate showed extensive sooty blotch. From the data,, it appeared that inoculum of Z. jamaicensis was not abundant on twigs at the time blossoms or apples were bagged, table 1. In addition to these data, 44 apples showing bitter rot, black rot, white rot, or other rots too extensive to permit evaluations for sooty blotch and flyspeck were also collected from the bags. Evaluations of sooty blotch and flyspeck development in 1975 showed index ratings less than 2 on apples bagged during the
TABLE 1. INCIDENCE OF SooTY BLOTCH AND FLYSPECK AT HARVEST ON APPLES ENCLOSED IN PLASTIC BAGS AT VARIOUS STAGES OF GROWTH DURING 19741

Dates Dates bagged

baggedApple growth
Bloom 3/ inch diameter 5/ inch diameter not bagged

Sooty blotch 1.9 1.5 1.9 4.7

Disease indices2

Apples

Flyspeck 0.2 .7 .7 2.9

harvested 913 40 29 38
11-25

April 9, 15, 23 April 30 May 7 August 15 (control)

i1Data

are averages from apples harvested from six trees on August 15. 2Disease severity scale: 0 - no disease, I -= trace, 2 = 2-10 percent, 3 =

percent, 4 = 26-50 percent, 5 = 51-100 percent of fruit surface diseased. 3Number of apples harvested per treatment; rotted apples were not included in
totals.

5Cyprex 65WP. [6]

blossoming period. Apparently, benomyl gave no disease control, since there was no difference in disease indices between benomyl and controls; however, captafol reduced sooty blotch to an index one-half that of the controls, and flyspeck was much lower than the controls, table 2. Similar results occurred with matured apples that were bagged in the juvenile apple stage.
TABLE 2. INCIDENCE OF SOOTY BLOTCH AND FLYSPECK ON BAGGED AND NONBAGGED APPLES FROM FUNGICIDE SPRAYED AND UNSPRAYED TREES IN 1975

Disease indices, Treatment Apples bagged at Blossom Juvenile apple stages stage2

not bagged

Benomyl ...-------__. Captafol ...Check . Benomyl _---32 Captafol ____ Check .... ___-------.....-

SOOTY BLOTCH 1.70 b4 1.51 b4 .56 a .60 a 1.94 b 1.52 b FLYSPECK a .09 a .16 a .25 a .07 a .22a

4.95 b5 .80 a 5.00 b 3.89 b5 .24 a 3.61 b

2-10 percent, 3 = 11-25 1Disease severity scale: 0 = no disease, 1 = trace, 2 26-50 percent, 5 = 51-100 percent of fruit surface diseased. percent, 4 2Blossoms were hand pollinated and bagged April 15, 17, and 21.
3Apples naturally pollinated and bagged April 24 and May 1 and 8.

4Means followed by the level of Duncan's Multiple SMeans followed by the level of Duncan's Multiple

same letters are not significantly different at the 0.05 Range Test. same letter are not significantly different at the 0.01 Range Test.

Applications of benomyl (1975) made at silver-tip, tight cluster, and petal fall did not reduce sooty blotch or flyspeck when the apples were not covered with plastic bags, table 2. Many of the apples on trees sprayed with captafol were free of sooty blotch and flyspeck infection at harvest; however, some phytotoxicity was evident in the form of fruit russet. Without the protective cover sprays, bitter rot, black rot, white rot, and scab developed. In 1976, applications of captafol at the tight cluster and near full bloom stages prevented sooty blotch and flyspeck infection. Disease indices of only 0.5 to 1.63, or 0.1 to 5 percent diseased fruit surfaces, resulted from captafol applications, table 3. Scab increased in captafol treatments which did not receive cover sprays of metiram. All fruit on three check trees had fallen by harvest time and that which had not rotted showed extensive sooty blotch and flyspeck infection.

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TABLE 3. EFFECTIVENESS OF FUNGICIDE APPLICATIONS FOR PREVENTION OF APPLE DISEASES AT THE NORTH ALABAMA HORTICULTURE SUBSTATION, 1976 Disease ratings Treatments Rate per

100 gal. 5 qt.2 5 qt.I 2 lb.3
-

blotch indexl 1.09 1.68 5.0

Sooty

speck indexi 0.52 .97 4.0

Fly-

Pct. scab
38.6 15.1 100.0

russet 20.6 19.9 14.6

Pct.

Captafol 4F Captafol 4F metiram 80W Check (unsprayed)

''Disease severity scale: 0 = no disease, 1 = trace, 2 2-10 percent, 3 percent, 4 = 26-50 percent, 5 = 51-100 percent of fruit surface diseased. 2Applications made pre-pink April 1 and near full bloom April 7. ISprays applied 14 times from April 19 to July 30.

=

11-25

TABLE 4. EFFECTIVENESS OF FUNCGIDE APPLICATIONS FOR PREEN'T'ION OF APPLE DISEASES AT THE NORTH ALABAMA HORTICULTURE SUBSTATION, CULLMAN, 1978 Disease ratings'

Treatments Captafol metiram
Dodine

Rate per 100 gal. 5 qt. 2 2 lb.3 0.5 lb.4 2 lb.3
-

Sooty blotch index' 1.01 a 1.43 a 4.73 b

speck index' 0.16 a .28 a
3.62 b

Fly-

Pct. scab

Pct. russet

0.2 a 1.8 a
90.1 b

0 0
0

metiram Check (unsprayed)

'Disease severity scale: 0 = no disease, 1 = trace, 2 - 2-10 percent, 3=11-25 percent, 4 = 26-50 percent, 5 = 51-100 percent of fruit surface diseased. 2Applications: green tip April 3, 1978. IMetiram applied 12 times from April 17 to August 18. 4Applications: April 10, 1978.

The single green tip (April 3) application of captafol followed by metiram cover sprays during 1978 resulted in an average disc ease index of 1.01 for sooty blotch and-0.16 for flyspeck, or about 1 percent sooty blotch and 0.2 percent flyspeck infected fruit surface, table 4. Apples from trees not treated with fungicides ,were severely diseased. The single green tip application of. captafol did not cause fruit russeting of the Red Delicious apples.

DISCUSSION
Sooty blotch and flyspeck developed on apples grown in plastic bags from hand pollinated blossoms in 1974 and 1975. These results agreed with studies made in other states and indicate that ascospores or conidia of G. pomigena and Z. jamaicensis are dis[8]

seminated as soon as temperatures are warm enough for blossom development (2,3,4,5,6,8). Early application of captafol to reduce or eliminate russet on fruit at green tip showed promise as an eradicant for a spring clean-up of inoculum that causes sooty blotch and flyspeck (10). These results indicated that infections by the sooty blotch and flyspeck pathogens occur early in the season. The single application of captafol recommended by the manufacturers for control of apple scab permitted only trace amounts of sooty blotch and flyspeck when followed by cover sprays. Fungicide cover sprays are essential since Z. jamaicensis has been reported from 78 species in 36 families of plants (3), and G. pomigena from 23 or more species (2). Many of these grow near apple orchards in Alabama, and may provide season-long inoculum. One application of captafol seemed to provide near season-long protection from sooty blotch and flyspeck. Scab and the summer rots caused by Botryosphaeria dothidea, Glomerella cingulata, and Physalospora obtusa were not controlled and required some applications of fungicides effective against these

diseases.

[9]

LITERATURE CITED
(1) BAINES, R. C. 1940. Pathogenicity and Hosts of the Flyspeck Fungus of Apple. Phytopathology 30:2 (Abstr.).
(2) AND M. W. GARDNER. 1932. Pathogenicity and Cul-

tural Characters of the Apple Sooty Blotch Fungus. Phytopathology 22:937-952.
(3) BAKER, K. F., L. H. DAVIS, R. D. DURBIN, AND W. C. SNYDER.

1977.

Greasy Blotch of Carnation of Flyspeck of Apple: Diseases Caused by Zygophiala jamaicensis. Phytopathology 67:580-588. (4) DURBIN, R. D. AND W. C. SNYDER. 1953. Ecology and Hosts of Flyspeck of Apple in California. Phytopathology 43:586 (Abstr.).
(5) GARDNER, M. W. AND R. C. BAINES. 1931. Cultural Characters and Host

Range of the Apple Sooty Blotch Fungus. Phytopathology 21:112 (Abstr.). (6) HICKEY, K. D. 1961. The Sooty Blotch and Flyspeck Diseases of Apple with Emphasis on Variation Within Gloeodes pomigena (Schw.) Colby. Diss. Abstr. 21:1699-1700. (7) , C. H. HILL, M. L. BOBB, AND C. R. DRAKE. 1972. Chemical Control of Diseases and Insects. In 1972 Virginia Spray Bulletin for Tree Fruits. Va. Poly. Inst. and State Univ. Pub. 219. 50 p.
(8) , F. H. LEWIS, AND C. F. TAYLOR. 1958. Time of Apple

Fruit Infection by Gloeodes pomigena and Microthyriella rubi. Phytopathology 48:462 (Abstr.).
(9) LATHAM, A. J. AND M. H. HOLLINGSWORTH. 1973. Incidence and Control

of Sooty Blotch and Flyspeck on Apples in Alabama. Auburn Univ. (Ala.) Agr. Exp. Sta. Cir. 208. 11 p.
(10) . 1979. Timing Captafol Sprays for

Control of Sooty Blotch and Flyspeck of Apples. IX International Congress of Plant Protection p. 181. (Abstr.). (11) MCGLOHON, N. E. AND H. C. ELLIS. 1978. Apple Spray Guide for North Georgia. The 1978 Georgia Agricultural Chemicals Manual. Coop. Ext. Ser., Univ. of Ga. Coll. of Agr. p. 254-257.
(12)
.

1978. Apple Spray Guide for Middle Georgia. The

1978 Georgia Agricultural Chemicals Manual. Coop. Ext. Ser., Univ. of Ga. Coll. of Agr. p. 258-260. (13) POLLET, D. K. AND R. W. MILLER. 1977. Commercial Apple Spray Schedule. USDA Coop. Ext. Ser. and Clemson Univ. Inf. Card 110. 8 p.
(14) POWELL, D., B. JANSON, AND E. G. SHARVELLE. 1965. Disease of Apples

and Pears in the Midwest. N. Cent. Reg. Ext. Pub. No. 16. Univ. Ill. Coil. of Agr. Coop. Ext. Ser. Cir. 909.

[11]

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With in aIgricultural research unit in every major soil area, Auburn University serves the needs of field crop, livestock, forestry, and horticultural producers in each region in Alabama. Every citizen of the State has a
stake in this research program. since any

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® Main Agricultural Experiment Station, Auburn.
s E. V. Smith Research Center, Shorter.
Tennessee Valley Substation, Belle Mina. Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman. Upper Coastal Plain Substation, Winfield. Forestry unit, Fayette County Foundation Seed Stocks Farm, Thorsby. Chilton Area Horticulture Substation, Clanton. Forestry unit, Coosa County. Piedmont Substation, Camp Hill. Plant Breeding unit, Tallassee Forestry unit, Autauga County Prattville Experiment Field, Prattville Black Belt Substation, Marion Junction The Turnipseed-Ikenberry Place, Union Springs. Lower Coastal Plain Substation, Camden. Forestry unit. Barbour County Monroeville Experiment Field, Monroeville. Wiregrass Substation, Headland Brewton Experiment Field, Brewton. Solon Dixon Forestry Education Center, Covington and Escambia counties. 21. Ornamental Horticulture Field Station, Spring Hill. 22 Gulf Coast Substation, Fairhope 1 2. 3 4. 5. 6. 7. 8. 9 10. 11 12. 13 14. 15 16 17 18 19. 20