Pests

• Grapevines attract a variety of pests including grape phylloxeras, grape berry moths, grape flea beetles, grape rootworms, Japanese beetles and redband leafrollers. Other pests include birds, rodents, squirrels, deer and opossums. Grape phylloxera is a tiny pest that forms galls on grapevine foliage, thereby impeding photosynthesis and causing leaf wilt and defoliation. The larvae of grape berry moths damage berries and blossoms as well as increase the likelihood of rots, mold and fruit flies. Adult grape flea beetles damage the foliage, causing leaves to appear lacy and skeletonized, while the larvae damage flower clusters. The larvae of grape rootworms eat smaller roots, reducing output and causing eventual death. Japanese beetles skeletonize the foliage, causing leaves to appear lacy and tattered. Redband leafrollers damage leaves, fruit and clusters.
  
  

Pest Management

• Although small infestations of grapevine phylloxera do not damage the plants, large infestations should be treated with an insecticide containing carbaryl during the bloom stage. Practice good sanitation during the winter to prevent grape berry moths and grape flea beetles from overwintering in plant debris. Treat the pests with an insecticide containing carbaryl or spinosad. Treat grape rootworms with a registered foliar spray when they are active. Handpick a few Japanese beetles, and add them to a jar filled with soapy water, or apply a foliar insecticidal spray containing permethrin or carbaryl. Use traps to catch leafrollers, or treat with timely applications of insecticide. Spread netting over grapevines to reduce bird damage, set traps to catch rodents and squirrels, and install a fence or barrier to deter deer.
  
  

Diseases

• Common grapevine diseases include powdery mildew, black rot, downy mildew and crown gall. Symptoms of powdery mildew include gray or white powdery fungal growth on the upper surfaces of leaves. Initial symptoms of black rot include tiny reddish-brown circular spots on the lower leaves. Left untreated, the lesions develop black borders and contain spores. Considered a serious disease of grapevines, downy mildew damages the fruit and foliage of grapevines. Crown gall disease causes galls on the roots or trunks of grapevines.
  
  

Disease Management

• Treat powdery mildew and black rot with a registered fungicide applied two weeks after bloom and then again three weeks later. Downy mildew responds well to timely fungicide applications, preferably applied before, during and after bloom. Because prevention is the best cure for crown gall, remove young grapevines with galls using sterilized pruning shears. Adopt good cultural practices to reduce plant stresses and help grapevines ward off diseases naturally.