Squash vine borer and squash bugs

Squash vine borer adults and squash bugs have been reported on vine crops in Southeastern Michigan. Squash vine borer moths are day-flying moths with a 1.0 to 1.5 inch wingspan. In flight, they look like wasps. There is one generation each year and adults emerge in late June/early July. They lay eggs at the base of squash plants, and upon hatching, larvae bore into stems (where they are protected from insecticides). Unless you scout fields for evidence of eggs or larvae, the first sign of squash vine borer infestation can be wilting vines in July and August. By that time, it is too late to do anything.

Growers should scout their pumpkin and squash fields weekly for squash vine borer from late June through early August. Examine the base of vines for evidence of larval feeding (sawdust-like frass near entrance holes) and then split open the stem to confirm the presence of larvae, which suggests more eggs are being laid. Two insecticide sprays, ideally applied to the base of the plants, and timed five to seven days apart, will control newly hatching larvae before they are able to bore into the stem. Consult Bulletin E-312, 2007 Insect, Disease and Nematode Control for commercial vegetables insecticides registered for control squash vine borer on your crop.

Squash bugs are serious pests of pumpkins and squash. Both adults and nymphs feed by inserting their beak and sucking juices from plant tissue. Large populations can cause partial wilting, and later in the season, squash bugs may feed on the fruit, causing them to collapse or become unmarketable. Adults are 0.5 to 0.75 of an inch long, flattened and grayish-brown. Wingless nymphs are similar in appearance to adults, and are whitish when small, with a brown head, and grayish white when larger. Eggs are laid in clusters usually on the underside of leaves and are orange when first laid, but turn bronze-colored before they hatch.

Squash bugs are virtually impossible to control later in the season when nymphs are large and the canopy is dense. The key to preventing squash bug problems is early detection and control of small nymphs. Growers should scout their field regularly for evidence of squash bug adults and eggs. Insecticides may be warranted if squash bugs are causing wilting of young plants (wilting is observed and squash bugs are present on the underside of leaves). Just before flowering, fields should be scouted for egg masses. This is the critical time to control squash bugs. If more than one egg mass per plant is found, an insecticide application is needed.

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