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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis
squashbug nymph

Squash Bugs

Posted by John Fulton -

The squash bug ranks as one of the lowest rated creatures on earth. Anyone who has grown squash, pumpkins, melons, or related crops has met it. Adult squash bugs are flattened in appearance and approximately ½ to ¾ inch long. Gray to black in color, adults are winged with orange and brown stripes visible on the edges of the abdomen. Eggs are 1/16 inch long, yellowish-brown to brick red in color. Upon hatching, nymphs are wingless, pale green to white with red legs, heads, and antennae. As nymphs mature, they become more gray in color with black legs.

Adults overwinter in plant debris around fields or wooded areas. Young nymphs present in late fall when temperatures begin to decrease will freeze and die off. In the spring, adults emerge as temperatures warm. At this time they fly in search of fields and begin mating. Females lay eggs individually in clusters of 7 to 20 on the undersides of leaves; each cluster is laid in a "V-shaped" pattern formed by two leaf veins. Eggs laying usually begins in mid-June and continues into summer. Eggs hatch in 1 to 2 weeks in late June and early July. Young nymphs feed in groups on the undersides of leaves. Squash bugs have five nymph stages in our area, and reach maturity in 5 to 6 weeks. Adults emerge in late summer and continue feeding until the first frost.

Damage to host plants is caused by both adults and nymphs. Young nymphs feed in groups near where they hatched, while older nymphs feed on the entire plant. Squash bugs suck nutrients from the leaves, disrupting the flow of water and nutrients. As they feed small, yellow specks develop on the leaves and later turn brown. Severe feeding may cause entire leaves to turn brown and die. Feeding by the squash bug also causes plants to wilt. Vines wilt from the point of feeding to the end of the vine. Leaves turn brown, then black, and eventually die. Wilt symptoms resemble symptoms of Bacterial wilt, a disease of cucurbits. However, if squash bug populations are controlled soon enough, wilted plants should recover. Plants infected with Bacterial wilt would continue to wilt and die. Both nymphs and adults also feed on the fruit. Severe damage may cause the fruit to be unmarketable.

Control of squash bugs is difficult. One way is to remove the eggs from the leaves. Of course, several have hatched out already. Sprays of pyrethroids, such as bifenthrin are effective against at least the younger nymph stages. The organic control has been sabadilla dust, but beware. Sabadilla dust is one of the most toxic things you can handle.

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