Homeowner Grape Insect and Disease Control Printable PDF version (2 pages) Grapes are produced in Mississippi home orchards both for home use and in local markets. Diseases and insects can be destructive, and anyone considering growing grapes must consider their control. Muscadine grapes are grown more often than bunch grapes in Mississippi because they are more tolerant to diseases, especially to a destructive disease called Pierce's disease. Whatever the size of your grape operation, you will benefit greatly from such sanitary measures as pruning, destroying the prunings by burning, and removing mummies and leaves in early spring before new shoot growth. MAFES/MSU-ES Bulletin 913 provides complete, detailed information on proper cultural practices for growing muscadine grapes as well as additional information on insect and disease control. Fruit Rots Black rot is a fungus disease that may completely destroy the crop's fruit. The fungus at first makes round, light-colored spots on the fruit and leaves that later develop a darker border. The whole berry soon shrinks and becomes a wrinkled coal-black mummy. This condition is responsible for the name black rot. Ripe rot and bitter rot are fungi that can also attack the fruit and cause them to rot, shrink, and form a mummy. Other fungi can attack the fruit and cause the flesh to harden. A good spray program normally controls all of the fruit rots. Foliar Diseases Numerous fungi can attack grape leaves and cause tan spots with dark borders. Some of these same fungi can also attack the fruit and tendrils. Dark pimple-like fruiting bodies can often be observed in infected lesions. Fungicides applied to control fruit rots normally provide good control. Pierce's disease is a bacterial disease that plugs up the vascular system. The bacteria are spread by leafhoppers. Symptoms on bunch grapes include dark red or brown leaf margins, delayed foliation, dwarfing of shoots, reduced yields, wilting, and often death of the plant. Remove and destroy infected bunch grape vines. Only a few muscadine varieties are affected by Pierce's disease, and it is rare for an infected muscadine vine to die. The usual symptoms on muscadine vines are brown leaf margins on one or more shoots. It is common for symptoms to occur on muscadine vines one year and not the next. Remove severely infected muscadine vines if symptoms occur two consecutive years. Aphids Aphids or plant lice are small soft-bodied insects that may or may not have wings. They are generally green, although some are pink, black, or yellow. They remove the sap from leaves, terminals, or stems, causing curled leaves and yellowish plants on many small fruit crops. They can also inject poisonous saliva or disease-causing organisms during feeding. They give birth to living young, resulting in tremendous numbers occurring in muscadine and bunch grapes. These insects secrete a material called "honeydew" that harbors sooty mold fungus, which can further spoil fruits. Grape Berry Moth The grape berry moth webs the grape berries together and causes them to turn black and drop from the stems when they are about the size of garden peas. Later generations eat small holes in the nearby ripened grapes and attach them with a web to a nearby leaf or another berry. The moths pupate in small silken cocoons folded in small semicircular flaps cut in grape leaves. The last generation of the season will spend the winter as a cocoon in these flaps in the fallen leaves. Grape Leaf Folder The larval stage of the grape leaf folder moth folds over the edges of the leaves and feeds on the tissues on the inside. It spends the winter as a pupa inside this fold in the fallen leaves. Grape Root Borer Grape root borers are serious problems in grape and muscadine vineyards. Moths lay their eggs on foliage or trunks of muscadines or grapes in July and August. On hatching, larvae burrow into the soil and tunnel the roots for almost two years. They then leave the roots and pupate in cocoons near the soil surface in June. A single larvae feeding on the trunk base (crown) can cause severe yield reduction. Monitor plants closely in May-June for poor vigor. It may be necessary to dig up plants to determine the infestation. Lorsban 4 EC is the only insecticide cleared for borer control in grapes and muscadines. Based on data from the trap catches, a single application of Lorsban should be made on or around July 20. Mix 4 1/2 pints of Lorsban with 100 gallons of water and apply 2 quarts of the diluted spray mixture to the soil surface on a 15-square-foot area around the base of each vine. Do not allow spray to contact fruit or foliage. Store Lorsban in original container in secured dry storage area away from dwelling. Spider Mites Spider mites usually reach damaging populations in hot, dry weather. Leaves become blotched with pale-yellow to reddish-brown areas and may eventually drop. Close examination of the underside of the leaf with a hand lens may reveal a fine webbing of silk. Mites can be found in this webbing or on the leaf surface. In severe cases, mites can also be found on the upper surfaces of the leaf. For adequate control of this pest, make several sprays at weekly intervals. Be sure to get good coverage of upper and lower leaf surfaces. Stink Bugs Stink bugs can be brown or green. They give off a disagreeable odor when crushed. They are large, shield-shaped insects and may or may not have distinguishing marks. They suck sap from developing fruit. This scars developing fruit, causing a "cat-facing" effect. The outside of the fruit may be marked with a small, pimple-like structure at the puncture site. Matured berries may result in dried brown droplets. Miscellaneous Insects Other insects that attack grapes include caterpillars, grape flea beetle, leafhopper, grape phylloxera, and grasshoppers. Homeowner Grape Insect and Disease Spray Schedule When to spray What to spray per 1 gallon water Remarks *Dormant Spray 6 tsp copper sulfate (bluestone) Apply after vines are pruned. Remove and burn all prunings. Good coverage is important. *First new shoot spray when shoots are 1 to 2 inches long (for bunch grapes only) 2 tb captan 50 W.P. or 1 tb benomyl 50 W.P. + Spreader-sticker Important spray against early black rot infection of leaves and stems. Do not use benomyl within 50 days of harvest. Captan has no time limitation. W.P. = wettable powder. **Second new shoot spray when shoots are 6 to 10 inches long Same as No. 2 spray Note benomyl limitation. Good coverage is essential. Important black rot spray. Prebloom spray just before blossoms open Same as No. 2 spray or 2 1/2 tb ferbam 76 W.P. + Spreader-sticker Do not apply ferbam within 7 days of harvest. Apply Sevin if feeding is present. Sevin can be applied up to the day of harvest. If aphids or spider mites are present, add malathion to spray. Post-bloom. Just after blossoms fall Same as No. 4 spray Note benomyl limitation. Important black rot spray. 2 weeks later Same as No. 4 spray Note benomyl limitation. Important black rot spray. 2 weeks later Same as No. 4 spray Note benomyl limitation. 2 weeks later Same as No. 4 spray Note benomyl limitation.   2 weeks later One of above fungicides + 4 tsp Sevin 21.3% L or 2 tsp malathion 57 E.C. +Spreader-sticker Do not use malathion within 3 days of harvest. If you use malathion E.C., damage may occur to some varieties. Do not use benomyl or ferbam within 7 days of harvest. There is no time limitation on captan or carbaryl. E.C. = emulsifiable concentrate. *These sprays are needed mainly on bunch grapes. **Continue sprays on bunch grapes, and initiate sprays on muscadine grapes at this stage. Note: Grape root borer control -- see discussion under Grape Root Borer. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and have label clearances. Always read and follow current label directions and restrictions on pesticide use. By Dr. J. Pat Harris, Extension Entomologist, and Dr. Frank Killebrew, Extension Plant Pathologist, and Dr. James Jarrat, Extension Entomologist Information Sheet 510 Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director Rev(500-7-00) Copyright by Mississippi State University. 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