Sap beetles are often considered minor pests, but the presence of large numbers of sap beetles on a host plant can prove economic in terms of crop damage caused by the feeding beetles. Impact on crop value is primarily due to the contamination of products ready for sale by adults and larvae. Sap beetles have also been recognized as vectors of fungi.
Adult sap beetles are small and vary in size from a ¼-inch or less up to a ½-inch. The end of the antennae are clubbed, which aids in their recognition. The surface of the wing covers are usually dimpled uniformly with minute punctures. Color is usually brown to black. The larvae of all genera are white with a light-brown head and have three pairs of small thoracic legs.
Survival And Spread
Sap beetles are characterized by a rather short larval development and comparatively long-lived adults. Pests have demonstrated a wide range of feeding habits. Sap beetles of agricultural importance such as the dusky sap beetle, corn sap beetle, and strawberry sap beetle have increased in number with the expansion in production of suitable crop hosts in Florida.
These pest species generally feed on fruits and other plant parts that are ripening or decomposing. Sap beetles cause both direct and indirect damage through their feeding activity. Feeding by primary insect pests such as the corn ear worm often provides entry sites for sap beetles. The strawberry sap beetle attacks ripe, nearly ripe, or decaying strawberry fruit by boring into the berry and is also a concern because of contamination of ripe fruit by beetles and possibly larvae. High populations may result in the spread of mycotoxin-producing fungi, which warrants control.
Field sanitation is an important means of control. Sweet corn, tomatoes, melons, berries, and other produce should be harvested immediately upon ripening. Damaged, diseased, and overripe fruits and vegetables should be removed from fields at regular intervals. Such material should be destroyed, or, if buried, should be buried deep below the soil.
Chemical treatment is recommended for the control of sap beetles in Florida. Several products are registered for use on corn and strawberries.
Research has shown that sap beetles are strongly attracted to certain volatile plant compounds in ripening or decaying fruits, producing pheromones that elicit an aggregating behavior. Baits using such material can be effective in trapping and monitoring sap beetle populations and help determine when treatment is necessary. Pesticides may also be incorporated in baits to trap incoming sap beetles.
Tight, long-husked, sweet corn varieties are more resistant to corn earworms and the beetle itself. Biocontrol research is ongoing, and an entomopathic nematode and a parasitic wasp have shown promise in some trials against specific species.