Wine taint caused when multicoloured Asian ladybeetles (MALB) (Harmonia axyridis) contaminate fruit at harvest is a concern for Ontario growers.
MALB, intentionally introduced to North America for the biological control of aphids and scale, did not establish well or reach high numbers until the accidental arrival of its favourite aphid prey species, the soybean aphid.
MALB populations in Ontario now increase over the summer in soybean fields, after which they move in large numbers to find food and to aggregate for the winter. After eliminating their preferred foods, they will feed and aggregate on grape clusters and be included in the fruit at harvest.
As B.C. lacks expansive soybean fields, MALB has not become a pest of grapes in the southern interior of this province and remains a beneficial species, helping to control leafhoppers, scale and other grape pests.
As the name suggests, MALB adults are variable in colour, ranging from black to light orange and with a variable number of spots. Distinguishing features are its large size and usually a dark "M" (or "W") on the white pronotum. It is the most common ladybeetle species in Ontario and also in the interior of B.C.
As for other ladybeetles that are also brightly coloured to warn off potential predators, ladybeetles produce a number of defensive compounds. One of several, isopropyl methoxy pyrazine, is higher in the hemolymph (blood) of MALB than in any other ladybeetle species.
