Grape Berry Moth
Although the Japanese beetle is rapidly moving to the top of the list in many areas of Maryland the grape berry moth (Paralobesia viteana; GBM) has typically been the most significant insect pest in the vineyard due to its direct and indirect damage to the berries and clusters.
- GBM is native to eastern North America and thrives in the region on wild and/or cultivated hosts (in the woods) and feeds only on grapes.
- GBM has multiple life stages (pupae, adult, larvae) and has multiple generations in the area depending on the weather of a particular season.
- GBM overwinters as pupae which emerge as adults in the spring, mate, and then lay 20 eggs on grapes.
- The newly hatched larva is creamy white with a dark brown head. As the larva grows, its body becomes greenish and eventually turns purple. The mature larva is about 10 mm in length.
- GBM larvae feed inside the grape berry, often requiring multiple berries to complete development.
- The mature larva will exit the grape and pupate either in a rolled leaf or in bark crevices or in the soil. After pupation is complete, adults will emerge, mate, and initiate another generation.
- First-generation adults begin to fly in mid-July, peak in early August, and continue to emerge until early September.
- The adult grape berry moth is small (6 mm long) and has an inconspicuous brownish appearance. The forewings are gray-blue at the base and become cream-colored with brown patches towards the tips.
- They are active mid-to-late afternoon until after dusk and have a distinct rapid, zigzag flight.
- Second-generation larvae feed only on the berries.
- They enter where berries touch each other or where the berry is joined to the stem.
- A single larva can do significant damage as it can move and feed successively on two to three berries and can damage up to seven berries.
Symptoms and Damage
- Often a reddish spot surrounds the point of larval entry. The discoloration can extend over half of the surface of an otherwise green berry.
- Injured berries ripen prematurely, split open, and shrivel, directly reducing yield and creating openings for secondary damage from rot organisms, fruit flies, and wasps.
- Infestations by the grape berry moth can vary greatly from year to year and are often very uneven in a vineyard, typically concentrated toward the vineyard area closest to a wooded border.
- Sex pheromone traps have been used to monitor the emergence and activity of male moths but have been limited in helping to determine the need and timing for control measures
- Effective control of GBM requires precise information about the timing of egg-laying and larval development.
- A degree-day model has been developed (Dr. Mike Saunders, PSU) to help to predict the various stages.
- Egg laying is well synchronized with the earlier bloom of native wild grapes so the date of wild grape bloom is a useful predictor for GBM emergence.
- A continuing total of degree days is maintained to identify when each generation is predicted to be
laying eggs: the first generation at 810 degree days, the second generation at 1620 degree days, and in early warm seasons, possibly a third generation at 2430 degree days.
- GBM’s synchronization with wild grape bloom means that most first-generation eggs are laid on wild grapes, rather than cultivated grapes, therefore no treatment is recommended for this first generation.
- First-generation adults begin to fly in early July, peak in early August, and continue to emerge until
- Efforts directed at chemical control of GBM should be targeted at the second and subsequent egg laying periods of GBM.
- To monitor for presence and damage, look for the reddish/purplish spots on the green fruit and webbing.
- The threshold for treatment is about 6% damaged clusters.
Control (Consult the commercial pest control recommendations, and always READ THE LABEL!
- To control light infestations, injured berries can be removed by hand.
- Control aimed at eggs and early hatched larvae is very effective. Intrepid, Altacor, and Belt are excellent options for these early egg-laying timings. Applied directly to clusters only, these three products have long residual activity, are relatively rainfast, have a low impact on beneficials, and good worker safety.
- Dipel and Biobit, (Bacillis thuringiensis – BT), narrow-spectrum treatments, are also an option.
- Delegate and Entrust are softer compounds derived from soil microbes (Entrust is OMRI approved/registered for organic applications). They are also labeled for Spotted Winged Drosophila.
- Where the grape berry moth is an annual problem, mid-season sprays (July-August) with insecticides such as the pyrethroids (Danitol, Baythroid, Mustang MAX) or Sevin or Imidan may be necessary if the problem is severe.
- Grape Berry Moth
Cornell University Library, eCommons
NYS IPM Type: Fruits IPM Fact Sheet
- Grape berry moth, Paralobesia viteana (Clemens)
Virginia Fruit Website, Virginia Tech
Timely Viticulture is designed to give those in the Maryland grape industry a timely reminder on procedures or topics they should be considering in the vineyard.