Lygus Bugs

Adults are yellowish, brownish, or greenish bugs, about 0.3 inch (7–8 mm) in length, with a conspicuous triangle in the center of the back that is tinged brown, red, or yellow. Nymphs resemble adults, but are uniformly pale green with red-tipped antennae and have no wings. Lygus feed on the fruit or seeds of many crops, including alfalfa, beans, sugarbeets and safflower, as well as a wide range of weed hosts. They can move to eggplant when their primary hosts dry or are disturbed, such as when alfalfa is cut, crops are harvested, or weedy fields dry down or are removed.

For additional information on identifying lygus bugs, see A Field Key to the Most Common Lygus Species Found in Agronomic Crops of the Central San Joaquin Valley of California, (PDF) UC ANR Publication 8104.

Lygus bugs feed by injecting phytotoxins into floral structures such as flower buds or small fruit. This feeding causes the floral structure to abort within days of feeding, and the structure is shed from the plant. Damage symptoms appear as dropped buds on the ground, and while there are several causes of fruit abscission (shed), lygus bugs are a primary culprit. Losses of floral structures relate directly to loss in yield as each bud or flower represents a potential fruit.

Because eggplant is maintained in a reproductive state for a long period of time through an extended harvest period, new fruiting structures can be vulnerable throughout the season. This makes management difficult because lygus bugs can migrate into a field at anytime, depending on the crops or weeds that surround the field. After the first floral buds appear, the plant remains susceptible to damage for the remainder of the season.

There is no published sampling method for lygus bugs. Sweep nets can be employed to locate populations and to determine the relative population levels, but the numbers are not related to damage. Walking through the fields during periods of warm temperatures causes the insects to fly off, so briskly walking and sweeping gives a better estimate of their numbers. The IPM guidelines for cotton and the sweep net techniques described may be somewhat useful with eggplant lygus populations (see http://ipm.ucdavis.edu/agriculture/cotton/lygus-bug-western-tarnished-plant-bug/)

Observations of flower and bud abscission coupled with presence of the pest on plants has been used by field personnel to make treatment decisions, but no reliable data are available to confirm these decision processes. Confirm that lygus is in the field because fruit drop may also be caused by heat. The use of sweep net samples to detect the presence of immature lygus bugs is a good indication of a resident population.