Notes on Grape Insects: Multicoloured Asian lady beetle
Multicoloured Asian lady beetles (MALB) vary widely in colour from pale yellow to deep red. These beetles also vary in size from 6-10 mm as adults and in number of spots with anywhere from 0 to 19 black spots on their elytra (wing covers). A series of black spots on the area behind the head forms a distinctive "M" pattern. Otherwise, these beetles are typical of most lady beetles in shape and overall appearance.
Period of activity
MALB are normally beneficial insects feeding mostly on aphids. Unfortunately, in late summer and early fall, these beetles become pests when they search for overwintering sites in homes and other structures, and when they feed on already damaged grapes and other fruit. Since aphids are the main food source for MALB, late season establishment of weeds in vineyards may support populations of aphids that are attractive to MALB.
Monitoring and thresholds
Lady beetles are of no concern for vineyard health or grape quality, except near harvest time. There are no established monitoring techniques and thresholds for late-season MALB in grapes. Begin monitoring for MALB several weeks prior to anticipated harvest date. Ten to 20 sites should be chosen in an average vineyard and at least five vines should be examined carefully at each site. These beetles can appear suddenly in vineyards so it is recommended to monitor daily for each cultivar in the last week before harvest.
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