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Scab and foliage diseases of pecan and their control

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Title:
Scab and foliage diseases of pecan and their control
Creator:
Large, John R.
Publisher:
Big Bend Horticultural Laboratory, University of Florida
Language:
English

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Source Institution:
University of Florida
Rights Management:
Copyright Board of Trustees of the University of Florida
Resource Identifier:
145507313 ( OCLC )

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BIG BEND HORTICULTURAL LABORATORY
Monticello, Florida

Big Bend Hort. Lab. Mimeo Report BBL 67-3 February 22, 1967


SCAB AND FOLIAGE DISEASES OF PECAN AND THEIR CONTROL

by J. R. LARGE, Associate Plant Pathologist

Pecan scab, Fusicladium effusum Wint., is the disease which causes the greatest loss of the nut crop in North Florida. There are eight diseases in addition to scab of economic importance on pecan trees.

Scab and the four leaf diseases listed below can be controlled by the regular spray schedule(l). Most seasons it pays to control leaf diseases on non-scabbing varieties. Two spray applications of bordeaux, Tri-phenyl-Tin hydroxide, or Cyprex in May and June will usually control the leaf diseases. The other diseases
are:

1. Downy Spot, Mycosphaerella caryigena, Demaree and Cole.

2. Pecan Leaf Blotch, Mycosphaerella dendroides Cke, Demaree and Cole.

3. Brown Leaf Spot, Cercospora fusca Rand, is a disease of minor importance.

4. Gnomonia Leaf Spot, Gnomonia dispora, Demaree and Cole.

5. Nursery Dieback, Botryosphaeria berengeriana de N., is controlled by pruning out the dead stems and twigs in the Fall. Repeat pruning in the Spring to remove any remaining infection.

6. Nursery Blight, Elsinoe randii, Jenkins and Bitancourt, is often severe in nurseries and is of minor importance in mature orchards. It is controlled by using the standard bordeaux spray schedule starting about the 5th of April.
/
7. Powdery Mildew, Microsphaera alni Wint., is of minor importance in
Florida. Control is obtained on non-scabbing varieties by two applications of 6-2-100 bordeaux applied in June and July.

8. Pink Mold, Cephalothecium roseum Corda., appears in late summer or Fall as pinkish fungus growth on hulls and in kernels. The fungus enters the nuts through scab or injuries. The scab control schedule will check this disease.

9. Crown Gall, Agrobacterium tumefaciens (E. F. Smith and Town) Conn., is a bacterial disease which causes wart-like growths at soil level. Do not plant diseased nursery trees. On orchard trees cut out the galls and paint wounds with a mixture of 1 part creosote to 3 parts coal tar. Do not cultivate or harrow close to infected trees as the machine will infect healthy trees.

PECAN SPRAY SCHEDULE

The pecan spray schedule consists of 5 or 6 sprays made at approximately
three week intervals beginning about April 10 and continuing until August 15. Do not spray unless you carry out a complete cultural program. The cost of a complete












program for a 25 year old tree in 1965 was estimated to be about $9.00(2). This included all costs with 6 scab sprays. This program will increase the yield of nuts from scab susceptible varieties 50 pounds or more per tree. Use the April insecticide spray and the May and June insecticide applications on scab resistant varieties(l). One of the least expensive spray chemicals for control of Pecan scab is bordeaux mixture in April, May, June and two July applications.

The most promising fungicides developed in the past 50 years are Tri-phenylTin hydroxide (Du-Ter), and N-dodecyl guanadine acetate (Cyprex). Du-Ter will control all diseases except powdery mildew. Add Sulfur W/P 2 lbs./100 or Karathane 1 lb./100 to the July and August applications if Mildew is present. Use Du-Ter 50 W at 4/10 lb./100 gallons. In very wet weather use 1/2 lb./l00.

The second most promising fungicide is Cyprex 2 lbs./lO0. Cyprex cannot be used in the April and May applications on the Moore and Van Deman varieties as the early applications cause marginal burning and necrosis of the young foliage. Excellent scab control was obtained in 1966 on the Big Bend Horticultural Laboratory pecan trees using alternate applications of Du-Ter and Cyprex applied with a speed sprayer. See pecan spray schedule Big Bend Hort. Lab. mimeo report BBL 67-4.

Varieties which appear to be Scab susceptible varieties:
scab resistant:
Schley Success
Curtis Mahan Frotcher
Elliott Pabst Van Deman
Russell Moore Mobile
Waukeenah Moneymaker
Farley scabs some, but Desirable started scabbing badly
appears to be somewhat near Cairo, Georgia in 1953.
resistant. Stuart is scabbing severely in
Alabama and Mississippi.


LITERATURE CITED

1. Large, J. R., John Van Duyn and H. W. Young 1967. Pecan Disease and Insect Control Suggestions. Big Bend Hort. Lab. Mimeo Report BBL 67-4.

2. Seale, A. D., Jr. 1966. Cost and Return for a Pecan Enterprise. Proc. Southeastern Pecan Growers Association 59: 15-34.


200 cc




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/ / ) . . I l,, . . , _ _ ),, ..,. J ~ J' . {_1 , . ) , ;'.) / 0..,, 1 ) , ( _ ' ) .,, . -~ ~ BIG BEND HORTICULTURAL LABORATORY Monticello, Florida Big Bend Hort. Lab. Mirneo Report BBL 67-3 February 22, 1967 SCAB AND FOLIAGE DISEASES OF PECAN AND THEIR CONTROL by J. R. LARGE, Associate Plant Pathologist Pecan scab, Fusicladium effusurn Wint., is the disease which causes the great est loss of the nut crop in North Florida. There are eight diseases in addition to scab of economic importance on pecan trees, Scab and the four leaf diseases listed below can be controlled by the regular spray schedule(!), Most seasons it pays to control leaf diseases on non-scabbing varieties. Two spray applications of bordeaux, Tri-phenyl-Tin hydroxide, or Cyprex in May and June will usually control the leaf diseases. The other diseases are: 1. Downy Spot, Mycosphaerella caryigena, Demaree and Cole. 2. Pecan Leaf Blotch, Mycosphaerella dendroides Cke, Demaree and Cole. 3. Brown Leaf Spot, Cercospora fusca Rand, is a disease of minor importance. 4. Gnomonia Leaf Spot, Gnomonia dispora, Demaree and Cole. 5. Nursery Dieback, Botryosphaeria berengeriana de N., is controlled by pruning out the dead stems and twigs in the Fall. Repeat pruning in the Spring to remove any remaining infection. 6. Nursery Blight, Elsinoe randii, Jenkins and Ditancourt, is often severe in nurseries and is of minor importance in mature orchards. It is controlled by using the standard bordeaux spray schedule starting about the 5th of April. 7. Powdery Mildew, Microsphaera alni Wint., is of minor importance in Florida. Control is obtained on non-scabbing varieties by two applications of 6-2-100 bordeaux applied in June and July. 8. Pink Mold, Cephalothecium roseum Corda., appears in late summer or Fall as pinkish fungus growth on hulls and in kernels. The fungus enters the nuts through scab or injuries. The scab control schedule will check this disease. 9. Crown Gall, Agrobacterium tumefaciens (E. F. Smith and Town) Conn., is a bacterial disease which causes wart-like growths at soil level. Do not plant diseased nursery trees. On orchard trees cut out the galls and paint wounds with a mixture of l part creosote to 3 parts coal tar. Do not cultivate or harrow close to infected trees as the machine will infect healthy trees. PECAN SPRAY SCHEDULE The pecan spray schedule consists of 5 or 6 sprays made at approximately three week intervals beginning about April 10 and continuing until August 15. Do not spray unless you carry out a complete cultural program. The cost of a complete

PAGE 2

-2program for a 25 year old tree in 1965 was estimated to be about $9.oo< 2 >. This included all costs with 6 scab sprays. This program will increase the yield of nuts from scab susceptible varieties 50 pounds or more per tree. Use the April insecticide spray and the May and June insecticide applications on scab resistant varieties(l). One of the least expensive spray chemicals for control of Pecan scab is bordeaux mixture in April, Hay, June and two July applications. The most promising fungicides developed in the past 50 years are Tri-phenyl Tin hydroxide (Du-Ter), and N-dodecyl guanadine acetate (Cyprex). Du-Ter will control all diseases except powdery mildew. Add Sulfur W/P 2 lbs./100 or Kara thane l lb./100 to the July and August applications if Mildew is present. Use Du-Ter 50 Wat 4/10 lb./100 gallons. In very wet weather use l/2 lb./100. The second most promising fungicide is Cyprex 2 lbs./100. Cyprex cannot be used in the April and May applications on the Moore and Van Deman varieties as the early applications cause marginal burning and necrosis of the young foliage. Excellent scab control was obtained in 1966 on the Big Bend Horticultural Labor atory pecan trees using alternate applications of Du-Ter and Cyprex applied with a speed sprayer. See pecan spray schedule Big Bend Hort. Lab. mirneo report BBL 67-4. Varieties which appear to be scab resistant: Curtis Elliott Russell Waukeenah Farley scabs some, but appears to be somewhat resistant. Scab susceptible varieties: Schiey Mahan Pabst Moore Moneymaker Success Frotcher Van Deman Mobile Desirable started scabbing badly near Cairo, Georgia in 1953. Stuart is scabbing severely in Alabama and Mississippi. LITERATURE CITED 1. Large, J. R., John Van Duyn and H. W. Young 1967. Pecan Disease and Insect Control Suggestions. Big Bend Hort. Lab. Mimeo Report BBL 67-4. 2. Seale, A. D., Jr. 1966. Cost and Return for a Pecan Enterprise. Proc. Southeastern Pecan Growers Association 59: 15-34. 200 cc


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