The squash bug, Anasa tristis, is a common garden pest that targets plants within the Cucurbitaceae family. These insects can cause significant damage to crops like squash and pumpkins. While often overlooked in favor of its preferred hosts, the squash bug certainly poses a threat to cucumber vines.
Squash Bug Diet and Preferred Host Plants
Squash bugs prefer Cucurbita species, such as winter squash and pumpkins, which are considered their primary host plants. Cucumbers, watermelon, and cantaloupe are secondary hosts susceptible to attack, especially when primary hosts are unavailable or pest populations are high.
Both adults and their immature counterparts, called nymphs, possess piercing-sucking mouthparts. They insert these mouthparts into plant tissue to extract sap and nutrients from the leaves, stems, and fruits. This feeding mechanism directly depletes the plant’s resources, leading to visible damage and overall plant decline. Research shows that while nymphs thrive on pumpkin, their survival rate is significantly lower on cucumber, indicating it is a less favorable, but still viable, food source.
Recognizing Specific Damage on Cucumber Plants
The feeding activity of the squash bug leaves bronze or yellow stippling on cucumber plants. As feeding continues, these spots merge, and the leaves turn brown, becoming brittle and dying.
A more severe symptom is localized wilting, sometimes called “Anasa wilt,” which occurs when heavy feeding disrupts the flow of water and nutrients through the plant’s vascular system. This wilting can be confused with bacterial wilt, a disease spread by cucumber beetles. Check the undersides of leaves for the characteristic egg clusters, which are shiny, oval, and typically copper or bronze-colored, often laid in V-shaped groups near the leaf veins.
Nymphs hatch with light green abdomens and black heads, progressing to a light gray color with black legs. Adults are flat-backed, brownish-gray insects, measuring about five-eighths of an inch long. Finding these adults or the clustered, gray nymphs hiding near the base of the plant or on the undersides of the leaves confirms an infestation.
Effective Management and Prevention Techniques
One of the most effective cultural practices is excluding the pest entirely by using floating row covers over young cucumber plants early in the season. These physical barriers must be removed once the plants begin to flower to allow for necessary insect pollination.
Maintaining a clean garden environment is important because adult squash bugs overwinter in plant debris, old vines, and leaf litter. Removing and destroying old cucurbit vines after harvest and tilling the soil eliminates these sheltered overwintering sites, reducing the population that emerges the following spring. Crop rotation further limits the pest’s ability to establish itself in the same location year after year.
Physical removal offers immediate control without chemicals. Gardeners should regularly inspect the undersides of leaves to handpick nymphs and adults, dropping them into soapy water. The distinctive egg masses should also be crushed or scraped off the leaves and destroyed.
Chemical treatments are most effective when timed to target the young, soft-bodied nymphs, as adults are difficult to kill with insecticides. Low-toxicity options, such as insecticidal soap or neem oil, can be applied to infested areas, ensuring thorough coverage of the leaf undersides. To avoid harming beneficial insects like bees, treatments should only be applied in the late evening after pollinators have finished their daily activity.