The fourlined plant bug traditionally has not been a common problem in Iowa. Very few samples have ever been diagnosed in the Insect Diagnostic Clinic. This year, however, I have received several samples and calls about this hemipteran.
Fourlined plant bug is well named. It is an attractive insect with 4 black stripes separated by three bright yellow stripes. The adult insect is slightly longer than 1/4 inch.
Fourlined plant bugs are not picky eaters and will feed on sap from over 250 different kinds of plants. Their piercing-sucking mouthparts puncture the leaves and sap is sucked from the tissue. The immatures (nymphs) feed from late April to late June, and adults are present the remainder of the summer, though they only feed until approximately mid July. The adults lay eggs in the fall, and when the eggs hatch the following spring, the cycle starts over. There is only one generation per summer.
The points where the bugs puncture the leaves show damage symptoms characteristic of this insect. Damage typically appears as a black or translucent spot, usually surrounded with a halo of different color. Injured areas may drop out of the leaf, leaving small holes.
Because fourlined plant bug is not a common pest in Iowa, we do not anticipate the damage and begin protective sprays in May when they would be of significant benefit. Late sprays applied after the damage becomes apparent and after the nymphs are grown are of no benefit. Since we are now at that point in the year, diagnosis of fourlined plant bug injury should not lead to spraying but rather to watering, pruning and other 'TLC' measures that promote plant health and recovery.
This article originally appeared in the July 1, 1994 issue, p. 103.