Hemiptera
Family:
Coreidae
Species:
Anasa tristis
Size:
The adult is 1/2 to 3/4 inch long.
Colour:
The adults are brownish/gray with orange markings along the edge of their abdomens. The nymphs are a whitish to greenish-gray colour with black legs and a dark head. As the nymphs move through their five instars, their colour ranges from light greenish gray to dark greenish-gray.
Description:
The adults have a flat back. The squash bugs, like stink bugs, produce a foul odor when disturbed. The last two instars have noticeable wing pads and look very similar to adult squash bugs.
Habitat:
The squash bug is found throughout the United States. It is a pest of all cucurbits, but prefers squash and pumpkins to other cucurbit plants. The squash bug is typically found on the underside of leaves and will try to find cover if exposed.
Squash bug eggs are usually found on the lower surface of leaves and are an iridescent bronze colour.
Life Cycle:
Adult squash bugs overwinter in plant debris or sheltered areas along field edges. The bugs move into the fields in the early spring to mate. Females lay eggs along the veins of the leaf surface, typically in a diamond or V-shaped pattern.
Egg masses may include from seven to 20 individual eggs. The eggs hatch in approximately one to two weeks. It takes four to six weeks for the nymphs to go through their five instars and develop into adults. In southern climates, two to three generations per year can occur.
Type of Damage:
Adults and nymphs feed in colonies using their piercing sucking mouth parts to pierce plants and suck the sap out. The bugs inject a toxic substance into the plants while they feed, causing the vines to wilt and eventually die. An entire plant or a section of a plant may die, while plants nearby in the same field may look healthy.
Adults and nymphs also feed on fruit and in some cases, make it unmarketable. Cucurbit yellow vine decline is a newly identified disease that can be transmitted by the squash bug. The disease is caused by the bacterium Serratia marcescens and attacks squash, pumpkins, and melons.
Although the disease has not been found in Virginia, cases have been reported in the bordering state of Kentucky, which may put Southwest Virginia at risk. Symptoms from the disease include stunting, yellowing, and decline in plant vigor typically one to two weeks prior to harvest.
In addition to yellowing leaves, the phloem in the plant stems turns brown and fruit usually must be culled as a result of the disease. The bacterium is able to survive the winter in the squash bugs and infect plants the following year.
Symptoms caused by cucurbit yellow vine decline are very similar to the symptoms of bacterial wilt, which is a disease transmitted by the cucumber beetle. Although bacterial wilt has similar symptoms, the progression of the disease is much slower than cucurbit yellow vine decline.
With cucurbit yellow vine decline, the plants rapidly turn yellow and wilt almost overnight. It is important to identify the pest causing the damage to properly treat the situation.
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