Let's Talk Squash Vine Borer and BT

[MissS]

Unfortunately BT is not a systemic that works in the vascular system. It you are injecting the BT into the interior hollow of the stem then it would not be entering the vascular system which is within the walls of the stem. It only is effective if it is ingested by it's target which is why you inject at the point of entry or as close as you can to that point. The only place on the exterior that the borer would ingest this is at the base of the plant while it is drilling which is why it is used on the stem where the larvae enter the plant. I would never inject my plants unless I knew that a larvae had already entered it. Using BT twice a week on the exterior should be enough. The aizawai strain of Bacillus thuringiensis is the strain that is most effective on the SVB.

https://extension.unh.edu/resource/mana ... fact-sheet

[Cranraspberry]

@MissS the way I understand it - you inject BT into the hollow stem, the inside stem walls get coated with bacteria. As the grub grows and moves along the inside of the stem it (hopefully) ingests the BT and dies before it does any serious damage.
Last year I sprayed and dusted the base of the stem religiously with Spinosad, but unfortunately 100% of our squash succumbed to SVB. With all the rain we get exterior application just doesn’t seem to do anything so hoping the injections will be more effective.

[Setec Astronomy]

@Setec Astronomy the math of trying to convert 1 Tbsp/gallon to the 9 ml I needed was a bit too much for me to handle

Ha, I mix up a quart using my 1.25 and 2.5 ml measuring spoons...what is that, a quarter teaspoon and a half teaspoon? Last time I actually injected about half the quart, and squirted the rest on the outside using my syringe because I was too lazy to find my spray bottle...am I already in the mid-season burnout?

[Setec Astronomy]

Well, I did another injection on my plants yesterday. I understand what MissS is saying, but I have been injecting in the hollow stems where it will run down to the woody parts. So far I seem to have no SVB's, where last year every plant got them. Last year I saw a moth, then put out my Trece trap...this year I can't find where I put the lure, so I haven't put the trap out...even though Trece assured me by email that the lure is only for the male moth and therefore shouldn't endanger my plants.

So I'm not sure if this is just luck, or what. I should mention that in the link MissS provided, it shows a SVB egg at a place that seems to be way up on the hollow stem.

[JRinPA]

Do it again like just like this next year! Don't mess with success.

[GoDawgs]

After having squash plants ruined every year this year is different. By now the plants transplanted out should have been long gone but are still producing and I didn't treat them with anything. But on the whole this seems to be an overall less buggy growing year anyway. Go figure.

[JRinPA]

My zuchini crashed, two plants adjacent, within a few days of each other. I only found a few borers, really no visible damage, so I don't think the borers killed them. They both collapsed back like striped cucumber beetle poison, so that's what I consider it this year. Collapsed just like cucumbers do here. And there were plenty of the beetles there.

[Setec Astronomy]

My zuchini crashed, two plants adjacent, within a few days of each other. I only found a few borers, really no visible damage, so I don't think the borers killed them. They both collapsed back like striped cucumber beetle poison, so that's what I consider it this year. Collapsed just like cucumbers do here. And there were plenty of the beetles there.

Striped cucumber beetle poison?!?!?!?!

You had to give me something else to worry about??

[JRinPA]

They are worse than borers for me, they kill zuch, cucumbers, and cantaloupe. Some say the spotted ones do it too, but I see striped to spotted roughly 10:1 here.

[Setec Astronomy]

Those look almost exactly like the three-lined potato beetles that like my ground cherries, except the cucumber ones are yellow instead of orange.

[pepperhead212]

Is this "striped cucumber beetle poison" you refer to that Bacterial Wilt, which at times seems to cause almost immediate wilting. I grow County Fair, as it is one of the two varieties that are resistant to the the wilt. The other, more recent resistant variety is a "Little Leaf" variety, which was not productive for me, though it did not get wilt. Almost every hybrid I have grown would end up getting wilt. I don't know about squash - I don't grow anything but butternuts, due to SVBs, which nothing ever worked for in my garden. And no moschata squash has ever gotten wilt, though cucumbers get it.

[JRinPA]

yes i do mean the wilt. It does not happen to butternut for me either. Zuchini, melons, cucumbers. The cucumbers and melons vine out so far, that it dies from the flower, in stages. With the zuchini, they each had a thick bush-vine, 3 foot or so and had already put out 10 good ones each with some pollination misses. And then bam every leaf yellow, but the vine was in good shape, borer wise.
This is how it looked 7/3 - I sprayed the vines exterior with BT that day just because I had some mixed up and left over:

01.JPG

02.JPG

Somewhere around a week or two later those good looking grey zuchini had every leaf go yellow just about overnight. I cut/broke each leaf off at the leaf base to get more sun in to the fresher leaves/flowers, but a few days later the whole plant was dead. The next day or two, plant #2 next door started the same process. I found very minor borer damage on autopsies. Plenty of yellow stripeys in the flowers.

If it wasn't bacterial wilt, I have no idea what it was.

[Setec Astronomy]

Well, looks like powdery mildew is going to be what takes out my squash plants this year, rather than SVB. I guess I should be digging out the copper spray.

[pepperhead212]

Maybe try spraying with a hydrogen peroxide solution, for the powdery mildew, and maybe the bacterial wilt, too. I use ½c/gallon, and don't mix with anything - H2O2 reacts with just about everything! I just sprayed just about everything in my garden with 2 gallons of that yesterday - helps with a number of things. Another cheap spray for mildew is baking soda or potassium bicarbonate, and if it's not getting too hot, some oil added to it. The only squash I grow is butternut, and fortunately, never have any problems with those, with just occasional prophylactic spraying.

[Setec Astronomy]

Pepperhead, what do you use for a sprayer? I've been using a Petra sprayer and they advised against using peroxide; I think right now I'm just going to mix some up in a quart spray bottle and see what it does.

[pepperhead212]

@Setec Astronomy I use a couple of different sprayers - I'd have to look at them, to see the brand, but they are old (one they don't make anymore), so the peroxide hasn't decomposed the rubber, plastic, or the seals. But I don't let it sit in it at all, and rinse it out every time.

[Setec Astronomy]

Are you talking about pump-up sprayers? My Petra is a battery-operated backpack (although I usually just carry it around), so I'm a bit loathe to take chances with the pump. It's hard to imagine the diluted peroxide would be much of a problem for most of these, though.

[pepperhead212]

Yes, just hand pumps on my sprayers.

[Setec Astronomy]

Ok, I was wrong--I got the powdery mildew under control...and now SVB's have taken out most of my plants. For some reason my Delicata don't seem to have been infected yet. I just BT injected the ones that weren't too far gone, last time was about 3.5 weeks ago.

[JRinPA]

Does SVB attack delicata? I don't believe it does mine. I do have something that died last week, squash patch, I'll have to check what it is.