Size varies from 0.38 to 0.5 inch long. In addition omnivorous leafroller larvae usually drop to the ground on a thread when disturbed, rather than dropping directly, as is the case with the grape leaffolder. Generally, there are four flight periods each year with a partial fifth in warmer years. The first of five larval instars appears a short time after a flights. The omnivorous leafroller can cause serious damage in California's Central Valley and North Coast vineyards.
Early harvest can also prevent infestation by fourth generation larvae.
Removing basal leaves will also improve coverage and efficacy of cryolite, Bacillus thuringiensis, and other pesticides. In warmer growing areas, be careful not to remove excessive numbers of leaves, which can lead to sunburned fruit. Such coverage is difficult in tight, nonthinned bunches so maximum effort to control this pest should take place before bunch closing. Evaluate omnivorous leafroller populations by sampling clusters beginning pre-bloom and continuing throughout the seasons. If even low populations are found at bloom or before, treatments may be warranted.