Why is My Squash Wilting?

Why is my squash wilting? Assuming you have been giving your vegetable garden adequate water, the Squah Vine Borer may be the cause.

Squash Vine Borer larva. Image Credit Matthew Orwat

Squash Vine Borer larva. Image Credit Matthew Orwat

 

Adult Moth. Image Credit Theresa Friday

Adult Moth. Image Credit Theresa Friday

Unfortunately presence of  the squash vine borer, the larval form of a clearwing moth, is usually noticed only after damage is permanent.  Prevention is possible with early recognition through vigilant scouting.

The adult moth is common in gardens throughout Northwest Florida, and is easily recognizable due to its black and orange coloration.The 1/2 inch moth is active during the day and will lay a single tiny orange egg at the base of healthy squash plants.

It only takes a week for the egg to hatch and for the larva to bore into the stem. Once the larva in inside the stem, it chews its way up the stem, blocking the transport of water from the roots to the shoots. By the time wilting is noticed, total blockage of the water conducting tissue (Xylem) is likely.

 

 

If the moth is noticed in the garden, preventitive application of Bt (Bacillus thuringiensis) or pyrethroid  (permethrin or bifenthrin) insecticide to the base of the stem may stop their incursion into the vine. Yellow traps full of water can be put out to monitor for them, since they are attracted to anything yellow.

Squash Vine Borer Egg. Image Credit Theresa Friday

Squash Vine Borer Egg. Image Credit Theresa Friday

If the vine is already affected, insecticide applications will not help. There is a slim chance of saving it by cutting out the larva. While performing this task make sure to preserve the stem and bury the stem of the plant in a few inches of protective soil. The plant may grow new roots and resume production.

For more information about the Squash Vine Borer, proceed to this University of Kentucky article. To learn more about pests of Cucurbits, check out this informative UF / IFAS publication, Insects Management for Cucurbits.

 

5 Comments on “Why is My Squash Wilting?

  1. Vigilant scouting is right! Nearly every morning I examine my squash vines for new incursions by these voracious larvae. I look for the “frass,” the chewed up plant that the larvae excrete, as it’s hard to see the holes. They attack all parts of my squash vines, from the main stem to leaf stems to veins in the leaves, but their favorite is the flower buds. It’s hard to see the hole in the base of the buds, but if I squeeze one gently and it feels soft, I can be fairly certain there is a grub in there. If it’s still firm, I leave the bud on the plant. The site of the incursion is often an orange color. If it’s in a leaf vein I cut out the affected part of the leaf and kill the grub, but if it’s in the stem of the leaf I usually cut the whole stem back to the main stem because I don’t like to leave those long hollow stems on the plant for other pests to enter and hide. If you attempt to cut a grub out of the main stem, cut lengthwise along the stem, not crosswise. When you see the larva, if you can’t get it out you can simply insert a stiff twig and crush it right inside the stem. Then as suggested, bury the compromised stem in soil. If the stem has grown upright and cannot be buried, you could wrap a short length of pantyhose around the wound and tie it off. I have managed to fend off two waves of borers, and my second squash harvest is coming on now.

  2. Sharon, thank you for the informative comment and for expanding on a point I just touched on in the article. I did not know that inserting a stick to crush the grub would be effective. I learn something new every day !
    Matt

  3. Last year I was pretty effective at curbing infection rates of the pesky svb by routinely injecting the hollow stems with liquid Bt. I picked up a large hypodermic and needle at my local feed and seed. Insulin hypodermic sizes are too small and will clog. We only have room in my church garden for a few squash bushes so they are high value. I just told the pastor not to worry if he saw me wandering around the garden with a hypodermic needle – I was just shooting up squash!

    • Karen, I like the injection technique, too. It works, but timing is everything. The svb’s beat me to it this year.

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