Squash bug

Anasa tristis (DeGeer)

Heteroptera: Coreidae

The squash bug is distributed throughout North and South America. Several other species in the genus coexist with the squash bug, feeding on the same plants but cause much less injury.

Host plants and damage

All cucurbit crops are subject to attack. However, Cucurbita pepo (squash), Cucurbita maxima (pumpkin), Citrullus lanatus (watermelon), Cucumis melo (melon), Cucumis sativus (cucumber), and Zea mays (maize) are the prefered host plants.

Squash bugs attack all plant growth stages and both, adults and nymphs feed in colonies and pierce host plant leaves, stems, and fruits with their mouth parts. While feeding they insert toxic substances into the host plants. As result plants can turn dark and/or dry. When infestations are severe fruits may not be formed. The amount of damage occurring on host plants is directly proportional to the density of squash bugs.

Morphology & biology

Adults are dark brown with grey in color and have a yellow underside. Often is the edge of the abdomen marked with gold and brown spots. They are about 14-16 mm in length and have a flat body. Typical for all true bugs are the needle-like mouthparts.

Female bugs deposit their eggs in masses on leaf surfaces or on petioles. Eggs are initially white and turn later yellow to bronze in color.

Nymphs hatch 7-14 days after eggs were laid. The five nymphal stages are approximate 2-20 mm long. First instars are green with rose-colored legs, antennae and head. Subsequent instars have dark legs, antennae and head. Nymphs are grayish-white with dark heads, legs and antennae.

Young nymphs are gregarious, a behavior that dissipates slightly as the nymphs mature.

In northern climates both sexes overwinter as adults. They live up to 150 days, depending on availability and quality of food.

Monitoring

Look for immature squash bugs on young plants near the base.

Pest management

Squash bugs are not often considered a severe pest of large-scale cucurbit production.

Biological control

Several natural enemies of squash bugs are known, principally Hymenopteran egg parasitoids.

The best known natural enemy is a fly in the family Tachinidae, Trichopoda pennipes (F.). The bright colored fly has a gold-black thorax and an orange abdomen.

Cultural control

Good fertilization produces vigorous crops, which can withstand an insect attack. Adult squash bugs will often be found feeding on old fruits or abandoned plantings. Clean cultivation can therefore reduce populations.

Leaves with egg masses can be handpicked in small fields and destroyed.

The use of squash or pumpkin as a trap crop to protect less preferred host plants such as melons and cucumbers is reported to be effective.

Chemical Control

Squash bug adults are often difficult to kill with insecticides. If material applied is ineffective apply an insecticide out of a group with different active ingredient. Nymphs are more susceptible than adults to synthetic insecticides.