Tiny red mites can be found mostly on leaf undersides, from mid-May through September. The mites also ingest the contents of cells, leading to a bronzing of infested foliage. Severe bronzing, especially early in the season, can result in a reduction in photosynthesis. This has implications for vine health and for fruit quality. When scouting in June, if you find more than 2-3 mites per leaf, treatment may be necessary.
Vines can tolerate higher mite populations later in the season.
By far, the worst insect pest of Long Island grapes is the grape berry moth . Eggs hatch in 4-8 days, yielding larvae that feed on young berries, often inside a protective webbing. Generally, 3-10 berries will be webbed together. Soon after fruit set, the larvae will bore into the berry and feed internally. One larvae may attack up to 7 or so berries.