Anasa tristis

Description

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

Host plants

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.

Life cycle

In the southern part of its range, the adult female A. tristis lays two or three batches of about 18 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 7-9 days into nymphs which have five instars. The first instar nymphs are green and about 2.5 mm 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 in length. The complete nymphal stage lasts about 33 days.

Damage

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 A. 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.

References

References

1. Arnold, 2001
2. Mertz, Leslie. (20 January 2016). "Squash Bugs Still Making Growers Crazy After All These Years". Entomology Today.
3. (1999-04-01). "Feeding Behavior of Larvae of Anasa tristis (Heteroptera: Coreidae) on Pumpkin and Cucumber". Environmental Entomology.
4. Capinera, John. (1 March 1999). "Squah bug: ''Anasa tristis''". IFAS.
5. H. B. Doughty, J. M. Wilson, P. B. Schultz, T. P. Kuhar, Squash Bug (Hemiptera: Coreidae): Biology and Management in Cucurbitaceous Crops, Journal of Integrated Pest Management, Volume 7, Issue 1, January 2016, 1, https://doi.org/10.1093/jipm/pmv024