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A Closer Look: Squash Bugs

Teresa Dorado

When walking through a field of winter squash in late August, the large green leaves cover the growing squash underneath. If we pay close attention to the leaves, we will most likely find shiny reddish-brown eggs uniformly spaced out on the underside of leaves. These are squash bug eggs.  

Squash bugs (Anasa tristis) are grey-brown and flat at their adult stage. New squash bug nymphs lack wings and have a green abdomen and red head, antenna, thorax, and legs. Over the following four to six weeks, they molt several times changing to a gray color with dark legs and antennae. Adults overwinter in field borders, wood piles or crop residues in the field. They have piercing mouth parts to suck the sap from leaves causing them to wilt and dry. Their feeding can also cause scarring on the fruit later in the season. At the Farm Hub, we monitor squash bug egg, nymph, and adult presence in the winter squash during the growing season. There were high numbers of eggs and nymphs this year, many nymphs hiding under the mulch in the field and scurrying away when we tried to get a closer look.  

Older nymphs under a leaf. They stay close together at the nymph stage but become more solitary as adults.

The smooth and shiny eggs in the field were intriguing, so we brought them in to get a closer look under the microscope. We captured a few pictures of the eggs when suddenly they started hatching and young nymphs started to slowly emerge. The process for one egg to hatch, from the egg cracking open to the young squash bugs wobbling on top of other eggs, takes about five minutes to complete. One by one they emerged until most of the young squash bug nymphs were out, slowly trampling on top of each other. It is not every day one gets to see these bright colored critters, with such detail, start their life cycle. Watch below a time laps video of hatching squash bug eggs.   

A squash bug emerging from an egg.
Time laps video of a hatching squash bug egg.

At high numbers, squash bugs can cause damage to crops. However, it is interesting to see them hatch up close. Their shiny egg masses on squash leaves and bright colored bodies at the nymph stage make them an exciting sight. 

Newly hatched nymphs are bright green in color with darker legs and head.

References:

Cornell Cooperative Extension | Squash Bug (ccecolumbiagreene.org) 

Squash Bug (psu.edu)  

Vegetable: Squash Bug | Center for Agriculture, Food, and the Environment at UMass Amherst

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