When squash leaves start to wilt inexplicably, no matter how much water is provided, I look for a hole in the stem somewhere. It may be a small hole, or a huge gaping wound like this one:
Sadly, this most often happens to mature, fruiting plants. I usually miss the first signs or forget all about them, and just assume the plants need more water. Not so! This terrible little beastie is the larva of a small orange and black moth with green wings that flies in the day. On first glance, the moth looks like a wasp, so it's hard to notice. It lays eggs on the leaves and stems of squash plants. The larvae then bore into the vines of all kinds of cucurbits, but squash are highly susceptible. The little caterpillar looks a lot like a 1" grub worm!
Unfortunately, it's very hard to control squash vine borers once they get a foothold in your garden. You can apply a carbaryl or permethrin product in the spring just as the blooms appear, as a preventative measure. For fall-planted squash, you may need to apply as soon as you plant. The treatment must be repeated per label instructions. Once the borers are inside the vine, they are hard to control with chemical measures. If you notice them quickly enough, you can slit the stem and carefully remove the borer. Then, you just have to hope that the plant will form new roots where you made the cut.
Alas! Only 2 zucchini harvested. That's what I get for not paying closer attention!
I'm happy to say I've never seen this borer here. Goodness, I didn't think anything could do so much damage to zucchini beyond deer and rabbits! One method of prevention that might be helpful is to use a fabric row cover over the plants, especially while they're young. We've found they help to physically exclude a lot of pests in the garden. I did find an info sheet for you too via ATTRA that might be helpful for your future squash plantings, I hope it helps:
ReplyDeletehttp://attra.ncat.org/attra-pub/PDF/squash_pest.pdf
Good luck!
I heard someone say that you could wrap the base of the stem with aluminum foil to prevent these pests. Has anyone else had luck with this method?
ReplyDeleteThanks to you both for the comments and for the info sheet! It's problematic to use row cover on the squash, because you have to have it in place early -- right when it's flowering. Which is right when the bees need to get in there! Victor, go right ahead and wrap your stems -- I found borers in the secondary as well as the primary stems! That's a lot of wrapping!
ReplyDeleteI am a nurseryman. I don't have time for a vegetable garden ;o)
ReplyDeletekeep aluminum away from the soil
ReplyDelete