When’s the best time to spray BT?

[nashobaTHC]

I have 6 outdoor plants in week 3 of flower and no signs of caterpillars on any of them. I’m wondering if I should spray BT before seeing caterpillars or after. Research indicates it must be consumed by critters to kill them and it needs to be reapplied after rains (so far not a problem in this drought). I’ve had some cats and minor bud rot in prior years so I’m trying to be proactive this year. Looking for advice from any outdoor growers with BT experience. Thanks.

 

[mancorn]

It’s important to spray early before flower when the worms are only able to roll leaves and can’t hide away. Once the plant is in flower the worms work their way deep into the flower and the Bt can’t really penetrate - and as you mentioned they have to eat the spray for it to work. It also breaks down pretty quick in the sun, so evening spray is best, which is also problematic in flower. If you’ve have them in the past, then for sure spray early.

I normally get a lot of the small skipper butterflies (don’t actually know they’re the worm source, but use them as a proxy) and was spraying back in May/June. But hardly saw anything in July/Aug and have just starting to see a few in the last couple weeks. Knock on wood maybe the drought is naturally knocking them back.

Edit: almost without exception the tallest part of the plant is the most susceptible. Rarely do I get them in the lower buds. (Some growers will plant corn or other tall plants close by.)

 

[nashobaTHC]

Perfect answer! I’ll be spraying this evening and I have a stepladder for spraying the upper branches. I also have Purecrop1 that I’ll use intermittently for the next 2-3 weeks then will just observe for caterpillars and WPM and treat if necessary (hopefully not necessary).

 

[freezeland2]

Perfect answer! I’ll be spraying this evening and I have a stepladder for spraying the upper branches. I also have Purecrop1 that I’ll use intermittently for the next 2-3 weeks then will just observe for caterpillars and WPM and treat if necessary (hopefully not necessary).

Next year start treating with BT much earlier. Like in early veg and up until flowering begins. Then no more.