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Flea Beetles

June 2, 2004

Flea beetles are being reported in various areas of the state on roses, flowers, and other herbaceous plants. Frequently, they are described by the public as looking like tiny Japanese beetles. In reality, they are metallic black, blue, or greenish beetles that are 1/16 to 1/8 inch long. They jump and fly when disturbed.

Damage appears as pinheadsized holes in leaves or window-feeding. Window-feeding occurs as the insect eats through one epidermis, usually the lower epidermis, and the mesophyll, leaving the remaining epidermis intact. The remaining leaf surface, or epidermis, is initially light-colored but soon turns brown as the tissue dry and die. These insects overwinter as adults and are most numerous after less severe winters.

There is a large number of flea beetle species, and they typically feed on only a few plant genera or maybe one family of plants. Thus, damaged weeds or other nearby plants usually do not result in their moving to other, more important plants later. The adult flea beetles are present for a few weeks until they lay their eggs and die. A few speciesí larvae appear as elongate, black, spiny larvae up to 1/2 inch long, feeding on the undersides of leaves. Most speciesí larvae live on the roots of plants, frequently a different plant species than the ones fed upon by the adults. It is uncommon for this larval feeding to require control.

Light feeding damage can usually be ignored. Plants with heavier flea beetle numbers or those experiencing heavy damage can be treated with carbaryl (Sevin), rotenone, or various pyrethroids labeled for the plant. Be sure to avoid getting insecticide on the blossoms so that butterflies, bees, and other pollinating insects are not killed.

Author: Phil Nixon


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