Squash bugs

Ken Johnson

A common pest of squash and pumpkins, and to a lesser extent cucumbers and other melons, are squash bugs (Anasta tristis). If left untreated they can cause significant damage to plants and fruit, if populations are large enough.

Squash bug adults are brownish-black in color with orange and brown stripes on the edges of their abdomens and about ½ to ¾ of an inch long. Adult squash bugs overwinter in plant debris and wooded areas and will begin to emerge as temperatures begin to warm in the spring. Females will begin laying eggs in mid-June and continue laying eggs into the summer. Eggs are laid in “V-shaped” clusters on the bottom sides of leaves or stems and are yellowish-brown to brick red in color. When the eggs hatch, wingless nymphs will emerge. They are pale green to white with red legs, heads and antennae. As they mature, the nymphs will become grayer in color with black legs and will grow up to ¾ of an inch long. Eggs will begin hatching over a period of a few weeks in late June and early July. Once hatched, nymphs will mature into adults in five to six weeks. Adults will feed on plants until the first frost, at which point they will begin to look for places to overwinter.

Both the adults and nymphs will suck sap out of leaves, stems and, later in the season, the fruits of plants using their piercing/sucking mouthparts. After hatching nymphs tend to stay grouped together, and as they age and become adults spread out throughout the plant. Small yellow specks will develop where they feed that will later turn brown. In severe infestations entire leaves may turn brown and die. If the bugs are feeding on the vines of plants the vines will wilt from the point of feeding to the end of the vine. Leaves will turn brown, then black, and eventually die if squash bugs are not controlled.

Feeding damage can appear similar to bacterial wilt, however if squash bugs are controlled quickly enough plants should recover. Plants infected with bacterial wilt will not. One way to test and see if a plant is suffering from bacterial wilt instead of squash bug damage is to cut a vine near the crown of the pant and cut it into two parts. Take these two parts and press them together. If bacterial wilt is present, there will be strand of bacterial ooze you can see when you gently pull the two sections apart.

Adult squash bugs are very difficult to kill. Therefore, scout your plants regularly so that infestations can be caught and treated while squash bugs are young. In addition to spraying, egg masses can be picked off of plants and destroyed. A board can be placed near plants and during the night both adults and nymphs will congregate underneath and can be disposed of in the morning. Make sure to remove plant debris in the fall to reduce overwintering sites and rotate crops.

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