Let's Talk Squash Vine Borer and BT

Setec Astronomy
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Let's Talk Squash Vine Borer and BT

#1

Post: # 75203Unread post Setec Astronomy
Mon Aug 01, 2022 6:33 pm

Boring preamble: I've got 5 squash plants on my deck in pots. Earlier in the season I was spraying biofungals every week or more, and I mixed BT in on GP's for caterpillars and because I read if you spray the stems of squash it will (may?) give a lethal dose to SVB larva on their way in. I didn't even know if I would have SVB's because I don't think anyone in the neighborhood has a garden, and where would they come from? So I sprayed the stems and looked intently on the stems for eggs. Then I saw a SVB moth! I quickly got a pheromone trap and placed it some distance away (but not too far) from my plants per instructions; it has caught a number of moths. Then it stopped raining and I stopped spraying (biofungal) and all of a sudden all my squash plants have SVB's. I already cut one down.

The point: Has anyone religiously (every 5-7 days) sprayed squash stems with BT and does that work to kill the SVB larva before they get started? I realize that's kind of trying to prove a negative.

If the answer to that is no, I was reading online about pre-emptively injecting (straight?) BT into the stems once a week using a syringe (so that's making a hole to do that) or injecting the BT into the stem through the larva entry hole to kill them after they are already in there--has anyone ever done this? I don't know if either of these really work, or if it's internet fantasy. Also, injecting straight BT seems like an awful lot since the spray dilution rate is a half ounce per gallon.
Last edited by Setec Astronomy on Mon Aug 01, 2022 10:17 pm, edited 1 time in total.

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PlainJane
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Re: Let's Talk Squash Vine Borer and BT

#2

Post: # 75209Unread post PlainJane
Mon Aug 01, 2022 7:29 pm

A lot of work …
I’ve only tried using light row covers and taking off during the day, on at night with limited success ( mostly because I forgot a few times.
Good luck!
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Re: Let's Talk Squash Vine Borer and BT

#3

Post: # 75213Unread post Vanman
Mon Aug 01, 2022 8:54 pm

I injected mine two or three times earlier this year with BT and also sprayed them with BT. We did not have any SVB this year. I do not know if we were just lucky or the BT did it.

In years past my wife has successfully performed surgery and removed SVB from the plant. She watched a YT video showing how.

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Re: Let's Talk Squash Vine Borer and BT

#4

Post: # 75215Unread post Sue_CT
Mon Aug 01, 2022 9:42 pm

I never had any luck splitting and removing them, there were always some that got missed. A large squash plant just has so many places for those little eggs to hide. I tried splitting and removing them and burrying the stem but it never rooted, just hung on for bit then died. It might all come down to just how much time you are willing to devote to it and how OCD you are about it, and finding every egg, making sure every stem gets treated, and looking for signs of infestation damage basically daily. I miss being to grow lots of it but not enought to make it my full time job, lol. I hope you have success, please keep us posted if you do. I would also love to know if you do, how much time you invest in the montoring and treatment of the plants. It would help others decide if they wanted to invest that effort or not to be successful.

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Re: Let's Talk Squash Vine Borer and BT

#5

Post: # 75218Unread post Setec Astronomy
Mon Aug 01, 2022 10:15 pm

Vanman wrote: Mon Aug 01, 2022 8:54 pm I injected mine two or three times earlier this year with BT and also sprayed them with BT. We did not have any SVB this year. I do not know if we were just lucky or the BT did it.
Did you inject with full strength BT, or diluted? How often did you spray?

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Re: Let's Talk Squash Vine Borer and BT

#6

Post: # 75227Unread post Vanman
Tue Aug 02, 2022 3:50 am

Full strength, spray ready, for the injection. Spray ready was all that was available locally at the time we injected for the first time. The second time I
mixed full strength to a spray concentration and used it both as a spray and to inject. We injected and sprayed about once a week three or four times. It might have been injected twice. I used a cattle syringe with needle from Tractor Supply.

We grow yellow squash, straight neck, and zucchini on stakes vertically so it is easy to inject and spray.

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Re: Let's Talk Squash Vine Borer and BT

#7

Post: # 75229Unread post worth1
Tue Aug 02, 2022 5:22 am

I first learned about these nasty things when an otherwise happy healthy plant collapsed over night.
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Re: Let's Talk Squash Vine Borer and BT

#8

Post: # 75232Unread post GoDawgs
Tue Aug 02, 2022 5:33 am

I've tried injecting the thick stems but they're too hard for my syringe. I have injected bT at times into the entry hole, directing the liquid both upward and downward but it didn't seem to make a difference. But I will try frequent application of bT to the plant bases... if I remember! We go through long rainless periods so that will help if I keep the stems dry when I water.

This is the first year ever I had no SVB problem. And in all the other years I've never seen the moth. This is also a year in whic I've encountered few stinkbug eggs too. Strange. Not complaining!

The last of the first planted straightneck squashes is kicking the bucket so I will remove it today and check for borers. The other more recent plantings are still healthy so maybe the problem plant is dying of old age. :)

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Re: Let's Talk Squash Vine Borer and BT

#9

Post: # 75242Unread post brownrexx
Tue Aug 02, 2022 7:15 am

I have injected bt concentrate and I thought that it did work but it is not easy and the needle clogs quickly with cells from the plant stem. It was very labor intensive and I did not feel that it was worthwhile. I think that I did it once a week the year that it worked.

Now I just expect that my zucchini and yellow squash will be infected so I just plant some new plants a couple of weeks after the first ones so that when the first plants die, the second plants are still producing.

This year with the drought and heat I didn't plant a second crop but the first one is still producing.

After my plants die I always split the stems with my pruners and kill any larvae that I find so that they can not get into the ground to pupate and complete their life cycle. Sometimes there are as many as 5 in one plant but usually only 2 or 3.

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Re: Let's Talk Squash Vine Borer and BT

#10

Post: # 101240Unread post Setec Astronomy
Fri Jul 07, 2023 6:51 am

Well, seeing when I started this thread last year, I may be counting my chickens before they are hatched, but this year I've been injecting my squash stems with (spray concentration) BT and so far everything is good. I got some actual sharp-needled syringes from Amazon and I've been injecting into the hollow leaf branches (on the theory it will run down to the main stem, I can't really seem to penetrate the main stem with the needle) about once a week, and squirting/spraying what's left onto the outside of the stem. We'll see if I can keep with that.

So far this seems to be working, but as I noted, it may be too early. Last year I had put out a SVB trap, but I'm thinking maybe it attracted more moths to the area...although I thought I saw somewhere that it only attracts the male moths. I think I'm going to contact Trece about that.

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Re: Let's Talk Squash Vine Borer and BT

#11

Post: # 101261Unread post Cranraspberry
Fri Jul 07, 2023 12:08 pm

I just injected mine for the first time today - bought 18 gauge needles on Amazon and they worked great. Last year I used standard “human” needles and it was impossible to get anything into the stem with those. We had the saddest summer squash harvest last year, so really hoping this season does better.
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Re: Let's Talk Squash Vine Borer and BT

#12

Post: # 101269Unread post Seven Bends
Fri Jul 07, 2023 3:28 pm

Which BT product do you use for squash vine borers? Is it different from cabbage worm BT? I used to use Dipel for cabbage worms, and that's the only BT I knew about back then. Now there seems to be a bewildering array of different BT products. I'd appreciate knowing the names of the specific BT products TJ people are using for SVBs and cabbage worms.

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Re: Let's Talk Squash Vine Borer and BT

#13

Post: # 101270Unread post Cranraspberry
Fri Jul 07, 2023 3:43 pm

@Seven Bends I’m using the basic Southern Ag brand Thuricide from Amazon, the same you’d use for caterpillars of all kinds. It’s a concentrate, so I diluted it with some water (kind of eyeballed it, but it’s a much stronger concentration than the 1Tbsp/gallon recommended for spraying).
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Re: Let's Talk Squash Vine Borer and BT

#14

Post: # 101283Unread post Setec Astronomy
Fri Jul 07, 2023 9:08 pm

Seven Bends wrote: Fri Jul 07, 2023 3:28 pmI'd appreciate knowing the names of the specific BT products TJ people are using for SVBs and cabbage worms.
Just using the Safer Caterpillar Killer, from Amazon.
Cranraspberry wrote: Fri Jul 07, 2023 3:43 pmit’s a much stronger concentration than the 1Tbsp/gallon recommended for spraying).
Hm. I just used the regular dilution. One YouTuber horticulture guy, after admitting that he doesn't have SVB's where he lives, insisted on doing a video anyway (I guess for the views or whatever it is on YT), where he injected it undiluted. But I'm sure he knew what he was doing :roll: (I got the feeling that he watched someone else's video first, copied it the best he could, and didn't read the BT directions...but what can I say...sometimes I'm cynical)

I get the idea of doing a stronger mixture, Cranraspberry, but BT works so well when you spray it on a leaf, it's hard for me to see it not working with the amount that's going in the plant by injection.

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Re: Let's Talk Squash Vine Borer and BT

#15

Post: # 101286Unread post JRinPA
Fri Jul 07, 2023 10:33 pm

I hope you are right Setec and it is working. For me it would be too soon to tell, since I just started seeing them a few days back and my two zuchini are not notably affected yet. It sounds like injecting might/should work, but I haven't tried it here. I did spray the outside of the base/stem once or twice this year.

I think they stuff I bought last year was the cheapest that week on amazon, GardenWay or something? It is brown and has a stink to it. The formula was the same, 1 tbsp per gallon. I like to add a little molasses as a sticker with sprays but haven't tried it this year, and I'm still using the same bottle even though they probably say to use within a year. I still think it's working on the exposed cabbage rows - I sprayed after seeing damage, every few days, and there hasn't been further damage.

I tend to agree with the thought that a trap just tells them where to come to. They have to be downwind to smell the trap; to get to the trap they need to tack back and forth into the wind, right? So what is the probability that they hit that trap on the first pass? Very likely it draws them to the area, and they may well find the squash instead. Male/female attraction, well if you draw the males then any females in the area are for sure going to have fertilized eggs to lay, right quick.

Also agree with the youtube thoughts, lots of those videos are by people that just want to be on youtube, not really great gardeners but more like thye use gardening as an in.

If the injections work that is great, but for me the definite solution would be to succession plant every 3 weeks or so and keep each plant covered until it is ready to rock. I looked over my two plants today and killed some squash bugs, tore off some squash bug eggs, but didn't see any SVB damage.

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Re: Let's Talk Squash Vine Borer and BT

#16

Post: # 101289Unread post Setec Astronomy
Fri Jul 07, 2023 10:59 pm

JRinPA wrote: Fri Jul 07, 2023 10:33 pmI tend to agree with the thought that a trap just tells them where to come to. They have to be downwind to smell the trap; to get to the trap they need to tack back and forth into the wind, right? So what is the probability that they hit that trap on the first pass? Very likely it draws them to the area, and they may well find the squash instead. Male/female attraction, well if you draw the males then any females in the area are for sure going to have fertilized eggs to lay, right quick.
I totally forgot earlier to relay that Trece got back to me and confirmed that the lure is for the male moths...but it's hard to argue with the above. On the other hand, if the female moths are going to be there anyway (attracted by the squash), putting a diversion for the male moths so they may not find a mate seems like it could be a good idea.

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Re: Let's Talk Squash Vine Borer and BT

#17

Post: # 101294Unread post GoDawgs
Sat Jul 08, 2023 5:31 am

I was just reading the updates on this thread and have the same problem getting a needle through the hard squash stem. Then an idea came creeping in. If one does not have a large gauge needle, maybe one could use a battery op drill with a small bit to drill a pilot hole for a smaller needle to inject through. Think that would work?

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Re: Let's Talk Squash Vine Borer and BT

#18

Post: # 101309Unread post Setec Astronomy
Sat Jul 08, 2023 8:21 am

GoDawgs wrote: Sat Jul 08, 2023 5:31 am I was just reading the updates on this thread and have the same problem getting a needle through the hard squash stem. Then an idea came creeping in. If one does not have a large gauge needle, maybe one could use a battery op drill with a small bit to drill a pilot hole for a smaller needle to inject through. Think that would work?
The question is if you inject in the drill hole, is the BT actually getting into the vascular system of the plant in that hard stem? Of course I don't know if injecting into the hollow leaf stems is getting in there, either. This is why instead of a bunch of un-vetted people on YouTube we need a university trial determining the relative effectiveness of this treatment and different variants of it. Who has a kid in college? Oh wait, my sister does.

The other thing is, is the damage from drilling going to be similar to the borer itself? Part of the reason I didn't inject into the stem was I couldn't get the needle in, but also I figured forcing it was going to damage the plant. Of course, I had to get over the part about putting holes in the stems I am injecting and what damage that is doing, if any.

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Re: Let's Talk Squash Vine Borer and BT

#19

Post: # 101317Unread post Cranraspberry
Sat Jul 08, 2023 9:36 am

@GoDawgs I suspect the BT would mostly pour out of the larger hole. I’m somewhat concerned about that with reapplication as well - I’m not sure I’ll be able to find the exact holes from last time, so the liquid might just trickle out of those.
The much thicker 18 gauge needles are working well for me though.
Last edited by Cranraspberry on Sat Jul 08, 2023 9:46 am, edited 1 time in total.
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Re: Let's Talk Squash Vine Borer and BT

#20

Post: # 101319Unread post Cranraspberry
Sat Jul 08, 2023 9:43 am

@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 😂, so I went with a stronger concentration. Given that it’s bacteria and not a systemic product I personally don’t see any harm in doing that, but I also don’t expect it to perform any differently than the recommended dilution. Empirically the folks over ar Houzz/Gardenweb report good results with a 1 tsp/cup of water ratio.
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