Zucchini Stem Damage

[ks.payne]

Hello, this is only my 2nd year trying to grow a vegetable garden. Noticed an issue with the stem of my Zucchini this morning. I think its insect damage? Any suggestions? I'm in northeast Kansas.

[PaulF]

That looks like squash vine borer to me. Prevention is the key for borers. At this stage it may be too late. You can slit the stem to remove the caterpillar and the plant may survive, but maybe not. For next year, look up prevention; there are several methods. In our part of the country borers are nasty to squash vines.

[pepperhead212]

Welcome to the forum KS!

I agree, that this is SVB, and if you have them there, you are in trouble! I have them here, and I tried countless things to prevent, and all turned out to be myths. The closest thing was radish greens - planted a patch of those, then a month later planted the zucchini, and I got several squash from each plant (often 1 or 2 were good, but often none), before they would succumb. Surround (kaolin clay compound) sprayed on helps, but there is no way to keep it on the vines at all times, as the new vine growth is there the next day! Bt injections will work, but again only temporarily, and with things like pumpkins, or other long vines, there is no way to keep up. And as many times you would be injecting these things, it would probably cost more than buying the squash! I also tried covering the row with Agribon, immediately after planting and after not growing squash for a decade, and they showed up! As you can see, these things are a problem here.

Butternut squash, and other moschata species are the only squash that I can grow, due to these pests. There is an Italian squash - rampicante - that is a moschata squash, that is sort of like a zucchini, but not exactly. I wasn't thrilled with it, as it got a sticky skin.

I gave up on growing the non-moschata species years ago. Now I am experimenting with Asian gourds, which don't seem to get SVB.

[rainbowgardener]

Agree. I have pretty much given up growing zucchini, due to the borers (and they are also susceptible to squash bugs and powdery mildew). Usually I get a big beautiful plant that produces one or two fruits and then collapses into a wilted mess practically overnight. I have tried various things but nothing has worked very much.

I had a couple squash plants volunteer in my garden. They are probably hybrids. They were making big round striped fruits. I kept piling dirt and mulch over the base of the stems where the borers attack. They lasted for awhile and weren't dead yet when I pulled them. But they were not withstanding our heat and dryness very well and getting very wilted every day, no matter how much I watered. And it didn't seem like they were growing the fruit any more. When I pulled them, the stem bases had in fact been attacked by the borers. They seemed to withstand it a little better than the zukes, but still I only got one fruit per plant.

One of the plants when I pulled it had tons of squash bug eggs and little gray-white nymphs on leaf undersides. So if it had survived the borer, the squash bugs would have gotten it. I destroyed the eggs and nymphs, so maybe I have reduced the next generation of squash bugs.

[pepperhead212]

I'm not sure why, but I never get squash bugs here, but I won't complain! It's not because they aren't in this region, because others have problems with them in my area. I'm thankful that they are not another one of my headaches!

I usually don't have powdery mildew problems here, but I did last year, because it was the second wettest summer ever, for this area. Still, I got so many butternuts that I still have 8 in the basement!

This season I have been spraying them with an aspirin solution - an experiment with the tomatoes, mainly, as this is supposed to help against their fungal diseases, but I also spray the squash, melon, and cucumber plants, since it is a cheap possible solution.

[rainbowgardener]

so far I have tried baking soda solution and hydrogen peroxide against the septoria on tomatoes, powdery mildew, etc. It slows the progress down, but I have to keep cutting off more diseased leaves and spraying again. Works better against septoria than powdery mildew.

[pepperhead212]

I have also tried these (actually, potassium bicarbonate, but about the same as baking soda) against the different diseases, and I have also found that the bicarbonate solution works better, but once established, it's hard to stop. The cucumbers were the worst last year; no problems this year, with an incredible amount of rain. No sign of mildew on squash, cukes, or others, with just the aspirin spray. KOW.

[dveg]

Re SVBs and Moschata, be aware that Moschata squash is "resistant" to SVBs. Doesn't mean that SVBs can't kill the plants, but just that it's a little harder for them to get in. The stems are not quite as hollow, and the stem walls are thicker. I ONLY grow Moschata, and I've lost plants regularly to SVBs. A strategy that works very well for me lately is to plant out late. In Texas here, SVBs are only active in the spring. So I plant out in late June, and have zero problems with them. Now, that works for me because my growing season is very long. I'll be harvesting squash in November. One of these years I'm going to try doing zucchini that way.

Your growing season probably isn't anywhere near as long, but you might investigate the SVB lifecycle in your area. That will tell you when you can remove netting, which is handy once you want the flowers to get pollinated.

[pepperhead212]

I have been lucky, and it seems like I have never lost one of my moschata squash to the SVBs. But years ago, a lady in FL told me that they are susceptible, and in her area it seems that they get worst in later summer, and she sees those moths everywhere. She also can't grow other species, but eventually, even her moschata plants succumb, though she still gets some butternuts.

That myth about them only being active early didn't pan out here (one of the countless things I tried!). I even planted some seeds in late August, and the plants still came down with SVB!

[dveg]

Well, where I am, it isn't a myth. I've been SVB-free for three years running now. Used to be out of business by May. Texas A&M ag has worked out the degree days during which they are active (and there are probably two generations, which gets us into June). It is possible where you are that the second generation comes out in midsummer. I believe SVBs don't like the heat much, and we have loads of it.

Addendum - let me be more specific. First generation SVB emergence is supposed to be around DD50=1000. For me, that's about April 1. Second generation emergence is supposed to be around DD50=2200. For me, that's around June 1. Egg laying happens soon after emergence, and it takes about 300 DD50 to hatch and start burrowing. That's just a few days for me. So by July 1, for me, it's all done.

See https://articles.extension.org/pages/65 ... ng-systems and work out your own DD50s.

Up north, everything will be later. Maybe much later.