Plan of Attack: Growing Squashes and Smiting the Squash Vine Borer (Updated!)

All my talk of luffa gourds last night has me thinking about growing squashes this year.  I have a longstanding love for squash of all kinds so there is never really a question of whether or not I'm actually going to grow squash.  The question is more often which types and how much.

Last year was a bust.  The squash vine borers got every last one of my squash plants and my replacement seeds did not do well in the severe drought even with extra coddling and care.  That's why there are so few pictures to accompany this blog post.


First wave of dying squash vines and their soon to be dead replacements.

It was, in a word, disappointing.  But this year will be different.  I have a plan. <insert hand wringing and maniacal laughter here>

Over the last few weeks, I've done some online research about squashes and the pests that love them. I Googled squash vine borer and got over 94,000 results.  That should give some indication of the severity of the problem this little clear-wing, day-flying moth causes every year.

But, as I said, I have a plan.  I have more than one plan, actually.  First and foremost, I plan to grow some varieties that have a natural immunity to the borers.  I've read conflicting information about genetic resistance. I understand that Butternuts are the first choice for resistant varieties. For summer squashes planting the non-bush types should help. I found this information sheet on the topic in one of my many searches.  Also, this forum thread was very interesting.

Before I start, let me just say that I am determined to make this work.  I plan to make this as difficult as possible for the borers.  If I have to plant in containers using fresh, sterilized soil every year then so be it.  Based on the information gleaned here are my plans:

1. The first plan involves a yet-to-be constructed cover that I plan to put over my squash seeds from day one immediately following planting.  The goal is to keep the borers from having any access at all to the plants until after the egg-laying portion of the annual cycle is over and done with.  From what I've read, putting a floating row cover over top of your squash plants until the female flowers appear is one way to keep the borers at bay.  If you're just not sure they're gone yet, you can even hand-pollinate the flowers  until you're sure the coast is clear.  I have an idea on how to make the covers sturdy enough to keep out the moths and big enough to allow the vines to grow undisturbed. I may do a tutorial on the construction process.  I have more than one design in mind.  I think this should work pretty effectively unless there are borer moths waiting in the soil where the squashes are planted.  As further insurance, I plan to spray regularly with insecticidal soap.  If these efforts should prove futile:

2. Two words: diatomaceous earth.  Another article I found described how one gardener put a heap of diatomaceous earth around the base of all of his squash plants.  Diatomaceous earth works to kill grubs, worms and other soft-bodied critters by being sharp enough to cut through their skin causing them to dehydrate and die. So as the eggs hatch and the grubs emerge, they crawl through the stuff and thus seal their own fates.  It is totally natural and non-poisonous although I'm told you don't want to inhale the stuff and get it down into your lungs.  That sounds icky.  Yes, it's a technical term.

3. Bacillus thuringiensis, a.k.a. Bt, is a bacterium commonly used as a pesticide.  It produces a crystal protein that affects the digestive tract of insects and causes them to die.  Unfortunately, it is not specific to grubs or worms so it takes a bit more work to protect beneficial species than just spraying it on the plant.  Another article I read suggested that a solution containing Bt should be injected into the affected plants to target and kill the grub that is destroying the squash vine.  I see this as a second to last resort in my squash vine borer arsenal.  But I'm not above it.  I'm not, I tell you.

4. I've read some good things about Montery Spinosad Organic Garden Insect Spray.  It's supposed to be very good at killing things like grubs, beetles and weevils but not harming beneficial insects like bees. (update 28 June 2013:  I have since learned that this is not the case.  It says right on the label not to spray on or near flowering plants as the bees will be killed.  Bummer.) I have not personally used this product. But if worse comes to worst, I will try it by spraying on the base of the plant near the ground.  One article suggested that this could also be injected into the stem of the vine to target and kill the grub within.  Another article touted its curative abilities in the squash bug arena. 

5. If none of those things works this year, then I guess I'll just have to buy from someone who had better luck than I did.  Last fall I ran across a guy at the farmer's market with a 16-foot trailer LOADED with butternut squashes. He said he had over a ton of squashes on the trailer and he had that many more waiting at home. He was selling them for $1 apiece and I felt like I was robbing him since the squashes in the store were almost twice that much per pound.  But he practically begged me to take them.  So I did.

Does all of this seem a little too much for some squashes?  Perhaps it is.  But at this point, it's the principle of the thing.