Squash Bugs by PJ LaRue Smith
A Texas vegetable garden usually contains several types of cucurbits – cucumber, squash/zucchini, cantaloupe, watermelon, pumpkin, and assorted gourds to name but a few. Often-heard amongst gardeners in late spring/early summer is frustration over the “sudden” death that has befallen their squash plants. In a row of plants, one will die, seemingly overnight, while the rest will carry on for a week or so before another suffers the same fate.
Many gardeners just attribute this to the hotter, drier weather, lack of rain, or simply a poor choice of variety. While any of these might be responsible for plant death, the “squash bug” (Anasa tristis) is the likely culprit, especially in plants that seem to be thriving one day and wilted/dying the next. (Squash bugs enjoy munching on all members of the cucurbit family, however, their favorite meal is the squash plant – hence the name.)
Adult squash bugs are brownish gray to dark gray bugs about 5/8 inch long and will be the first of their kind to be seen. Emerging in the spring, they mate as the plants begin to vine, laying yellowish to bronze-brown eggs in clusters on the underside of leaves, often in vine angles. (Egg laying is not limited to just their host plant, as eggs can be found on tomatoes and even t-posts.) When first hatched, nymphs have a green abdomen with crimson head, thorax, legs and antennae, later becoming grayish-white with nearly black legs and antennae.
Squash bug eggs hatch in one to two weeks, with nymphs feeding in clusters on the stems of the plant. In six to eight weeks, they transform into adults which will continue to feed through the fall. Damage to the plants will show as a rapid wilting of the leaves which will then blacken, become crisp and dry.
Squash bug damage can be particularly detrimental to young, immature plants. Many entomologists believe this is due to a highly toxic saliva that is secreted into the plant during feeding. Without question, the amount of damage occurring on a plant is directly proportional to the density of squash bugs. While foliage tends to be the primary focus as a food source for the squash bug, the stems and fruit are also fed heavily upon. Such intensity of feeding on a given plant can cause an entire plant, or section of plant, to die, while nearby plants remain healthy.
Squash bug adults are unusually difficult to kill with insecticides. Adult control can be accomplished if the correct material is selected, however, it is more effective to target the nymphs. A word of caution – cucurbit production requires pollinators, specifically, the honeybee – pesticide application while blooms are present should be done with extreme care. Apply one that has little residual activity and do so only late in the day when there is minimal honeybee active in the garden.
The tendency of squash bugs to aggregate in sheltered locations can be used to advantage by the home gardener. Placing boards, large cabbage leaves, or other shelter for squash bugs induces them to congregate there during the day, simplifying there removal and disposal.
Eliminating crop debris in a timely manner is also very important. Squash bugs will often be found feeding on old fruit or in abandoned plantings, so clean cultivation is essential to reduce the overwintering population. Good garden hygiene has been shown to be the easiest, most effective organic means of controlling this pest.