Squash Bug

The squash bug, Anasa tristis (De Geer) (Hemiptera: Coreidae), is a common cucurbit pest in the United States. It uses piercing-sucking mouthparts to feed primarily on stems, but also attacks leaves and fruit. Heavy infestations can reduce yields and spread disease. Populations typically increase throughout summer.

Females lay clusters of about 20 eggs, usually on the underside of leaves. Eggs are oval, approximately 1.5 mm long and 1.2 mm wide (Bonjour et al. 1990). They are a light gray when first laid, but quickly change to a copper-orange color (Doughty et al. 2016; Fig. 1). They usually hatch in 7-10 days.

The squash bug has five nymphal instars. Newly hatched nymphs are about 3 mm long, light green, and have reddish heads, thoraxes, and legs (Fig. 2). Later instars become gray with black heads and legs. Nymphs increase in size with each molt, with wing pads developing during the fourth and fifth instars (Fig. 3). Development takes approximately 4–6 weeks,

after which nymphs molt into adults.

Adults are grayish-brown, about 1.5 cm long and 0.8 cm wide (Fig. 4). They emerge in spring, typically around May, after overwintering under plant debris, boards, or rocks. Egg laying begins by mid-June. Squash bugs typically have one generation per year, although a partial second generation may occur under favorable conditions.

Squash bugs feed on most cucurbits but prefer summer squash and pumpkin for feeding and egg laying (Bonjour et al. 1990; Doughty et al. 2016). Egg laying and nymph survival are higher on yellow straightneck, crookneck squash, and pumpkin than on cucumber or muskmelon (Bonjour & Fargo 1989). Hubbard squash is also a host but generally supports lower nymph survival.

Squash bugs feed on plant xylem, causing wilting, leaf necrosis, and, in some cases, plant death (Doughty et al. 2016; Fig. 5). Feeding can reduce yield and weaken plants' resistance to secondary stressors.

Squash bugs can transmit Serratia ureilytica, a bacterium