By Kylee Sherod, University of Minnesota Extension Intern, Wright County
Are you seeing small beetles feasting on your fruits and vegetables?
Glischrochilus quadrisignatus, otherwise known as picnic beetles or sap beetles, are insects that appear in gardens to feed on overripe and decaying produce. The beetles are commonly found on corn, tomatoes, raspberries, strawberries and muskmelons.
To identify a picnic beetle, look for small, oval, black beetles. They are typically ¼ - ½ an inch long and have four orange spots on their wing covers. The small beetle eggs are typically found in plant matter and are milky white. Larvae grow to be about ¼ an inch long and are white to pale yellow with a light brown head.
Beetles can be found emerging in the spring. From then, they lay eggs in various plant materials. The larvae appear for three weeks before transforming into pupae. This transition typically occurs in late June to early July. The entire egg to adult development takes place in 30-35 days, however; there is only one generation of picnic beetles each year.
Picnic beetles first enter a garden due to damaged, fermented, or overripe fruits and vegetables. Once established in the garden, they may begin to injure intact fruits and vegetables. Produce they may leap to first include berries and corn.
To protect your garden from picnic beetles, it is essential to remove overripe fruits and vegetables. It is important to completely eliminate these sources of food for the beetles or bury them deep into the soil.
Another option for garden mitigation is to place bait traps to reduce the beetle populations. This can include fermented plant juices and buckets of overripe fruit. If incorporating traps in a garden, be sure to place them a few feet outside of the garden and discard them every few days. The use of pesticides to remove picnic beetles is not recommended as they are not effective.
Be watchful of pests, including picnic beetles, in your garden during this tough summer. For more information on picnic beetles, visit https://extension.umn.edu/yard-and-garden-insects/sap-beetles. Wright County residents can call 763-682-7394 for questions related to yard and garden items.