If you have cucurbit vegetables such as pumpkins or summer and winter squash on your gardening list, you can expect squash bugs to find their way to your garden. These common pests can do an enormous amount of damage to winter squash and pumpkins in particular, but they may strike related cucurbits such as melons and cucumbers. By understanding these squash bug basics before problems arise, you can keep squash bugs from stealing your cucurbit crop:
Adult squash bugs are dark gray-brown and measure about 5/8 inch long. In some adults, gold and brown spots alternate along the edge of the abdomen. Their shield-like shape often gets them mistaken for broader-shaped stink bugs, but squash bugs only damage cucurbits. Stink bugs are much less particular. Adult squash bugs typically live up to 130 days, and two generations per season are common. Adults lay very distinctive shiny, copper-colored eggs beginning in late spring or early summer, which soon hatch into hungry offspring known as nymphs.
During the 33 days before full adulthood, squash bug nymphs molt repeatedly and pass through five stages called instars.1 Light green nymphs emerge from eggs and become progressively larger and darker gray with each instar stage. Both nymphs and adult squash bugs feed on cucurbit plants, often congregating in very large numbers.
When feeding, mature and immature squash bugs pierce the tissue of cucurbits and suck out the plant juices. They feed on leaves, vines and even fruit. The damage done by squash bugs is particularly destructive; they pierce plants at multiple sites, causing vines and leaves to collapse as they suck the sap.
In addition, squash bug saliva released during feeding carries bacteria that are toxic to cucurbit plants. This causes the injured leaves to wilt, and eventually the plant dies. In some cases, infected nymphs and adults carry the cucurbit yellow vine disease bacterium. Also transmitted via saliva, this pathogen may kill plants that might otherwise survive a squash bug assault.1