Sap beetles often become a nuisance in gardens during late summer. They feed on damaged, overripe, or decomposing fruits and vegetables.

Identification
Most sap beetles are small, between 1/8 and 1/4 inch long, and oval in shape. They are black or brownish, sometimes colored with orange or yellow. The antennae of sap beetles have a club (knob) at the end of them. The most common species of sap beetle in home gardens is the picnic beetle, Glischrochilus quadrisignatus. They are 1/4 inch long and shiny black with four orange spots on their wing covers.

Biology
Picnic beetles overwinter as adults. They emerge in spring and lay eggs near fermenting and decaying plant material. Larvae feed for about 3 weeks and then pupate. They finally emerge as adults in June or July. Picnic beetles take about 30-35 days to develop from egg to adult. There is one generation each year.

Adult beetles are attracted to any fermenting smell and are commonly found around garbage containers, beer and wine, food served outdoors and gardens where fruits and vegetables are being grown. Picnic beetles commonly infest corn, tomatoes, raspberries, strawberries, and muskmelons that are wounded or overripe.

Injury
Sap beetles do not normally attack healthy, intact fruits and vegetables. However, if they are attracted to a garden by fermenting, overripe produce, they may also infest undamaged, developing fruits and vegetables, particularly berries or corn.

Management
Sap beetles are difficult to manage. Sanitation is the most effective means of reducing beetle numbers. Remove and destroy damaged or overripe produce. Harvest produce as it ripens. This helps eliminate both the odor and availability of susceptible fruits and vegetables.

Insecticides are not very effective in managing sap beetles. Some degree of control can be obtained in severe infestations by using malathion or carbaryl (Sevin). These insecticides may kill existing beetles, but as long as food odors are present, they can not prevent additional sap beetles from moving into gardens.

It is important to remember that there is a waiting period after an insecticide has been applied before you can harvest and use the produce. Read the pesticide label to determine the harvest interval for specific vegetables and fruits you wish to treat. It is most effective to use a product with a zero or one day waiting period. Be sure the plant you wish to treat is listed on the pesticide label of the product you plan to use.

Caution: Always read pesticide labels carefully before buying products and again before using them. The label is the final authority on how you may legally use a pesticide.

E217S
Revised 9/99