Watch out for multicolored Asian ladybeetles during grape harvest
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
The multicolored Asian ladybeetle is an effective biocontrol agent of soft-bodied insects during the summer, but grape growers and winemakers should be concerned about this insect around harvest time because of the potential to contaminate the harvest. The 2007 season has not been ideal for growth of aphids (the ladybeetle’s main food), and so populations of multicolored Asian ladybeetle are relatively low in Michigan this year. It is still a good idea to scout your vineyards for this pest in the coming weeks so there are no problems with crop contamination. Very low levels of multicolored Asian ladybeetle in fruit can taint the flavor of juice and wine. The bottom line is to be alert for the potential threat as harvest approaches and have a plan.
Regular scouting of ripe blocks can help detect ladybeetles before the harvester is running through the vineyard. Research in Minnesota has shown that beetles show up on yellow sticky cards before they move to the clusters, so a few yellow traps can provide an early warning. Checking clusters is still a good idea, and if the beetles are found on the fruit just prior to harvest, there are some insecticide options with very short PHIs to consider. Research in Michigan, Ohio and New York has found that products containing azadiractin (e.g. Azadirect), imidacloprid (Provado Pro), and pytrethrum (Evergreen) have activity against multicolored Asian ladybeetle and can be used to minimize cluster infestation. In recent tests by Roger Williams at Ohio State University, Venom insecticide has given up to four days of excellent activity against multicolored Asian ladybeetle, and was one of the most active products tested. With a one day PHI, and multicolored Asian ladybeetle on the label for this insecticide, Venom is a valuable tool for grape growers. Baythroid is a pyrethroid insecticide that has also shown high activity against multicolored Asian ladybeetle, and it has a three day PHI making it a potential option for this use. Mustang Max is another pyrethroid, with a one day PHI, and also expected to have high activity on this insect.
Any use of insecticides for multicolored Asian ladybeetle control close to harvest should be discussed with your processor or winemaker. It would be worthwhile having this discussion now to discuss how to tackle this pest if it appears just before harvest when everyone is very busy.
For more information on this insect, and how to identify and manage this pest in fruit crops, please see the MSU IPM website: http://www.ipm.msu.edu/beetleFruit.htm.
Identifying multicolored Asian ladybeetles
Multicolored Asian ladybeetles may be many colors with several or no spots. They can be distinguished from other ladybugs by the black M or W (depending on the viewing direction) between the head and abdomen (see photos).