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Keep on the Look Out for Squash Vine Borer

PHOTO: Adult Squash Vine Borer. Photo credit: Jeff Hahn, University of Minnesota Extension

University of Minnesota Extension, Stearns County News
July 5, 2017        
Source:  Beth Berlin, Extension Educator-Horticulture
University of Minnesota Extension
Stearns, Benton, & Morrison Counties

Keep on the Look Out for Squash Vine Borer
By Beth Berlin, University of Minnesota Extension

ST. CLOUD, Minn. (07/05/17) —The end of June and early July is the time to keep a close eye out for the squash vine borer. This insect will impact the growth of your vine crops, largely attacking the summer squash, winter squash, and pumpkins with less impact typically to your cucumber and melons. Here is some helpful information about what to watch for and how to protect your vine crops.
The squash vine borer, Melitta curcurbitae, adults will emerge from underground cocoons at the end of June and beginning of July. The adults resemble a wasp’s shape even though they are a moth. The adults are ½-inch long with an orange abdomen and black dot.  It has two sets of wings, the first being metallic green and the back pair being clear; although seeing both sets may be challenging at first glance.
The adults will lay eggs singly, which are flat, brown, and about 1/25-inch long, at the base of a vine crop.  The eggs hatch in approximately one week after being laid and the larvae will feed through the vine to the center of the stem.  This damage will block the flow of water to the rest of the plant causing it to wilt. The larvae will feed for 4-6 weeks and then will exit the vine and burrow into the ground to pupate until the following summer.
Signs of infestation include wilting of the plant. In heavy infested gardens, complete crop loss can occur.  Under closer investigation you will notice holes near the base of the plant filled with the larvae’s frass, which resembles green to orange sawdust. The base of the stem may become mushy and rot.  It isn’t uncommon for several larvae to attack the same plant.
Options for management include:
1) Monitor for adult moth activity
2) Inspect for egg deposits at the base of the plants
3) Use floating row covers for about two weeks as soon as adults are detected; do not use covers when plants are flowering or in areas where vine crops were planted last year as you may be trapping in newly emerging adults that overwintered there
4) Use insecticide treatment if necessary
Insecticide treatments include products containing carbaryl, permethrin, bifenthring, or esfenvalerate.  Begin treatment when the bines begin to run which is typically last week of June or early July when the adult squash vine borers are active.  Read and follow all safety and application instructions. Typically a minimum of two applications is necessary, repeating every 7-10 days until the end of July.
For more information about the squash vine borer visit

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