Strawberry Sap Beetle
The pest status of the strawberry sap beetle, Stelidota geminata (Say), has been accelerated along with the change in marketing systems from grower harvesting to pick-your-own operations. Unskilled pickers leave large numbers of ripe and overripe berries in the field, which attract the beetle.
The strawberry sap beetle is small, oval, and less than 1/8 inch long. It is brown and has a slightly mottled appearance. In extremely overripe berries, another sap beetle, the picnic beetle (Glischrochilus quadrisignatus or G. fasciatus) also might be found. The picnic beetle is larger and has four orange blotches on its back.
As the berries begin to ripen in May and June, adult sap beetles are attracted to the patch. They attack ripe, nearly ripe, or decaying fruit by boring into the berry and devouring a portion. On sound berries the sap beetles usually gain entrance from under the berry, eating a hole straight into the berry. This occurs more often when the fruit is in contact with the ground or the mulch layer. The hole can be seen if the fruit is picked, but it is not usually conspicuous unless several sap beetles are working together. The adults are seldom seen because they fall to the ground and scurry away when fruit is disturbed.
The primary injuries caused by strawberry sap beetles are the cavities eaten by one or, more commonly, by a group of beetles. The beetles also disseminate organisms that cause rots in the fruits and carry these to other fruits as they move about. Any damage to the berries near harvest, such as other insects' attacking the fruit or mechanical injury, might stimulate an invasion of sap beetles. Larval damage is much less obvious because it occurs in decomposing fruit, but it is the worm-infested fruit that is of concern to the grower and consumer.
Cultural control is useful in the reduction of sap beetle outbreaks. Removing damaged, diseased, and overripe fruit from the patch at regular intervals is known to assist in reducing populations. Problems with sap beetles often arise with the buildup of overripe berries when rain occurs during harvest. Boxes or flats of harvested berries should be removed from the field immediately or covered to keep beetles out. Provide pickers with special containers for unmarketable berries and bury the boxes as soon as possible. Pesticides can be used, but they are not as effective as the cultural control practices.