Notes on Grape Insects
Multicoloured Asian lady beetle
Identification
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.
Learn more...
