Anasa tristis is a species of bug in the family Coreidae. It is a major pest of squash and pumpkins, found throughout North America, and is a vector of the cucurbit yellow vine disease bacterium. These bugs can emit an unpleasant odor when disturbed. It is commonly known as the squash bug but shares this name with certain other species.

The adult Anasa tristis is a greyish-brown, somewhat flattened insect reaching a length of about 1.5 cm (0.6 in) and a width of 0.75 cm (0.3 in). There is often a row of alternate brown and gold spots along the margin of the abdomen. Adults survive for three or four months.

Description

Anasa tristis can be found on various members of the gourd family Cucurbitaceae, but most often occurs on pumpkins and squashes. Some varieties and cultivars are more susceptible to attack than others. Research has shown that nymphs can grow to adulthood with varying degrees of success on different host plants; 70%, 49%, 14%, 0.3% and 0% survived to maturity on pumpkin, squash, watermelon, cucumber and cantaloupe melon respectively.

Host plants

In the southern part of its range, the adult female Anasa tristis lays two or three batches of about eighteen eggs, but in the northern part of the range it just lays a single batch. The eggs are oval, somewhat flattened and bronze in colour, and are deposited on the underside of the leaves of the host plant. They may be clustered close together or more widely dispersed but are often regularly arranged. The eggs hatch after seven to nine days into nymphs which have five instar stages. The first instar nymphs are green and about 2.5 mm (0.1 in) in length. Each successive instar is larger and less hairy and grey. The fifth instar is grey, with developing wing pads and about 10 mm (0.4 in) in length. The complete nymphal stage lasts about 33 days.

Life cycle

Anasa tristis is a true bug that feeds by sucking sap, mainly from the leaves, but sometimes also the fruit. Historically, at least as far back as 1902, some gardeners believed that Anasa tristis had toxic saliva, however more recent research from 1993 suggests the process of harming plants does not involve any toxins. What happens is that the insects physically damage the xylem and leaves of the plant, which causes them to wilt, darken in colour and die.   The heavier the infestation, the greater the damage to the plant. Sometimes one plant or part of a plant can be heavily attacked while surrounding plants are untouched. Besides the direct damage their feeding causes to the plant, these insects can act as vectors for cucurbit yellow vine disease caused by the bacterium Serratia marcescens. This disease can kill the plants.

Damage

harmful

bite

Anasa tristis, commonly known as the squash bug, is considered a tree pest because it feeds on various species of trees, including fruit trees and ornamental plants, causing damage to the foliage and weakening the overall health of the trees.

tree pest

Anasa tristis, also known as the squash bug, is considered a garden pest because it feeds on various types of plants commonly found in gardens, such as squash, pumpkins, and cucumbers, causing damage to the leaves, stems, and fruits, which can lead to reduced crop yields.

garden pest

Anasa tristis, commonly known as the squash bug, is considered a crop pest because it feeds on various crops such as squash, pumpkins, and cucumbers, causing damage to the plants and reducing crop yields. Its feeding behavior can lead to wilting, stunted growth, and even death of the crops if left uncontrolled.

crop pest

Anasa tristis is considered a pest because it feeds on various trees, garden plants, and crops, causing damage to the foliage, stems, and fruits, which can lead to reduced crop yields and weakened overall plant health.

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