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.

AAAUUUGGGHHHH! Blog Episode One: The Squash Vine Borer

I suppose it had to happen sooner or later. This gardening season was going very nicely. No major problems except for the odd little weevils that attacked, skeletonized and destroyed the mustard greens in my mesclun salad mix. It was ONLY the mustard greens. Apparently, we have very discriminating weevils in Nebraska. Who knew?

I dislike the mustard greens anyway, so no biggie to me.

But this. This is unacceptable.

I stepped out to the garden to water the plants in pots and examine the tomatoes for peak ripeness. That's when I noticed the squash plants didn't look right. By 'right' I mean they didn't look green and upright. In fact, they looked downright yellow and wilty.

So I grabbed the hose and, as I started watering, wondered how on earth I could have missed them yesterday. Upon closer examination, the truth was revealed: tiny, itty, bitty little sawdust-y holes at the base of some of the vines.

Squash vine borers! AAAUUUGGHHHH! I almost choked on my gum.

After a few moments of impolite comment, I reluctantly pulled out the vines that looked the worst and examined the remaining plants for holes. Not all of the vines were affected and, after some research, I concluded that they must be the butternut squashes I planted. Butternuts, for some reason, seem to be less affected by the borers. I'm still working on my seedling labeling skills so I'm not really sure which varieties are still alive.

Here's what I learned about the borers today: Squash vine borers overwinter in the ground as pupae and emerge in the summertime as adult, clearwing moths whereupon they set out in search of a likely looking squash plant on which to mate and lay eggs. When the eggs hatch, the little larva bore into the vines and take up residence inside the stem blocking the flow of water and nutrients to the plant which eventually dies. Once the larva matures, it digs down into the ground to pupate so it can emerge next year to ruin someone else's squash plants.

Lovely.

Organic controls of the squash vine borer are aimed more or less at prevention rather than destruction. Basically, the idea is to exclude the adult moths from your baby vines. This is best accomplished by learning to identify the adult moths and then, once you spy them buzzing around, using floating row covers or another mesh type barrier with tiny holes to keep the adults from laying their eggs on your plants. The eggs are most likely to be laid during the second half of June or so in my neck of the woods so putting up the covers for a few weeks during June and July should do the trick.

If you really want to try to save the affected plants you have, there is one thing you can try. Sterilize a sharp knife and use it to slit the stem of the affected vine upward starting at the point where the larva bored into the stem. When you locate the larva (or larvae), stab the heck out of it/them with the knife. Then carefully reposition the vine and bury the cut portion in the garden with dirt and keep it moist. With luck, the vine will put down more roots where it is buried and the plant may live. Then again, you might wind up with a dead squash plant buried neck deep in your garden.

Fortunately for you and me, the borers only have the one generation every year. So, chances are they have probably done the damage they were going to do already. It's going to be close, but I think I can set out another planting of seed and maybe get a few squashes before winter sets in. The seed packets all say 95-105 days to maturity and I have right about that many days until first average frost. I have nothing to lose but the rest of my squash seeds, right?

At least next year, I'll be ready for them. The little...darlings!