In the Garden: about squash bugs

Why are pumpkin or squash plants looking mottled and dried up? Squash bugs are a common pest of the cucurbit family: squash, zucchini, pumpkins and melons. They are called "stink bugs" because of the foul odor they exude when crushed.

Squash bugs, Anasa tristis, can be a significant problem on cucurbits. Leaves may develop small specks that turn yellow, then brown beyond the point of attack. Vines start to wilt, and parts of the plant blacken, turn crisp and die. If infested plants survive, their yield can be reduced.

Squash bugs hide in leaf axils, along leaf veins, on the undersides of leaves or on the fruit itself. If the population density is high, the bugs are obvious. The winged adults are gray, yellow-brown or black. They are flat-backed, often speckled. An orange or orange-brown stripe borders the abdomen.

The wingless nymphs are smaller versions of the adults, but have a reddish head and pale green to almost white abdomen without a stripe. As they age, squash bugs turn brown.

The eggs, laid in clusters of a dozen or more from late spring through midsummer, are yellow-brown to bronze ellipses. They hatch into nymphs within approximately 10 days. The nymphs turn into adults within four to six weeks.

Squash bugs suck out the sap of a plant causing a speckling effect around the point of insertion. Damage tends to be localized.

Squash bugs are challenging to control. Early plantings are more susceptible to damage. Choose resistant cucurbit family varieties. Rotate crops and avoid planting cucurbits in the same place as the previous season. In case of infestation, avoid planting these family members for one year. Monitor areas where cucurbit crops are planted and remove bugs and eggs. Handpick bugs off plants. Trap them by placing boards in and near the garden and turn them over daily and kill or vacuum up the bugs. When the bugs congregate on just a few leaves, cut the leaves off and put them in the garbage. Do not compost infested plant parts. In spring and early summer, search and destroy the egg masses.

Since these bugs overwinter as unmated adults in protected places in mulch, old plants or weeds, remove all plant debris from the garden after harvest. Leave the garden site clean and free of hiding places for overwintering bugs. Natural predators such as the tachinid fly and wolf spiders can help to control squash bug populations.

Chemical insecticides are temporary solutions, because populations resurge within a few days or weeks. Insecticides can also damage cucurbits. Better alternatives are to reduce the number of reproductive adults and practice good garden sanitation.

Photos and more at http://picasaweb.google.com/jimsloan3/SquashBugs

JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at 887-2252 or skellyj@unce.unr.edu