Any idea of how I can rid my plants of whiteflies before I take them into the g'house? I sprayed quite a bit before I took them out this spring, but there are some that still have them. A large potted lantana had them so bad that I just gave up and cut it back hard last week, and sprayed with Azamax. I have too many huge plants to be able to spray them with it. I've found the best way for me to get spray on everything is dump the spray in my water tank in the g'house and use my regular watering nozzle to spray so I get good coverage and plant foliage saturation.

It sounds like you've dealt with them way more than me, so I this might not be much help, but I dealt with whiteflies with a combo of neem and parasitic wasp release, and ladybug/green lacewings.

I don't think that is an option for me, as I have a large greenhouse and take in "boarder" plants for the winter. I'm sure that's how I got such an infestation. I spray after I get everything in in the fall and make an effort to spray twice a month for the first couple of months, and then monthly thereafter.

Too bad you can't put a little ladybug house inside your greenhouse and invite a ton of them in.

A little bit of dish soap in your water tank and use the hose to spray everything really well, a week before, and then again right before you move them all in? Might work. I think like mites, you need to spray at least twice with soap to get the next generation as the eggs hatch.

Unless you're going to treat every plant with a systemic, I think the mechanical means is the most effective.

We're being told (down here in commercial grower's land) that the strains of whitefly bred in commercial greenhouses are now getting really resistant to most of the systemics anyway so they're really not much use, aside from being expensive and nasty.

From what I understand, whiteflies don't live through our winters. Does your greenhouse ever get below 0 out there in WI?

If my g'house got below 58, I'm in trouble. I overwinter all my stuff in there. And plants for clients.

Elaine, I wonder how the dish soap would work if I sprayed now and put it in a hose end sprayer, one where I can dial the amount to mix in...............

That should work great, Anna as long as you can dilute the soap enough. About a tablespoon per gallon works for me. Or just rinse it off once you're sure you've sprayed thoroughly.

Well, how long do you think I should let the soap stuff set on the plants before I rinse off? If I can do it while they are outside a couple times or more before it's time to take them in, that would be ideal for me. I have so many............

Just enough time for the soapy water to get down into all the leaf axils and other nooks and crannies. Ten or fifteen minutes should do it.

I'm sure you know not to spray with soap when the sun is shining on the plants, too? It can make them burn.

I guess I would have forgotten that. Thank you for the reminder. I imagine that will suds to H and gone, putting it out the end of a hose-end sprayer. LOL

So if I get heavy-handed, will soap that gets down and into the roots hurt the plant? I know I'm going to have to get really spray-happy with the ferns that I see whiteflies zooming out of when I water.

I wouldn't think so, but maybe do the soap spraying when the plants need watering anyway, and then you can flush the pots with plain water. A little soap might evict any passengers in the pots, too as a bonus.

Is there any dish detergent that is better? I have some Dawn that I want to get rid of. I HATE the smell of it, but someone got it for me. I use Ivory Liquid. But if there is any brand that is better, I can get that.

Some people think Dawn has too much detergent, but I asked the local entomologist and he said it doesn't matter. Any old soap will do. Use up the Dawn!

I have no experience with a greenhouse, but I have brought plants and/or cuttings into the house for winter. I wash them with soapy water before bringing in . I also use a systemic killer on at least some of the plants as I think it helps to break the cycle of exploding populations of bugs. Any bug killed by eating the treated plants can't have babies... So if you can't treat all the plants with a systemic, but do some of them, I think it helps in controlling them.

Karen

Karen, do you rinse the soapy water off after a bit like Elaine does?

No. But I don't use much soap, either. It hasn't seemed to hurt them. I try to keep my yard pretty much organic, so I sometimes spray my outdoor plants with soapy water too, for bugs. It never seems to harm the plants. On an online soil forum, some guys once told me to use Ivory liquid, but I don't even remember why they said the Ivory was preferable.

But I think if you use a systemic insecticide even on only a few plants, when the bug bites that treated plant it dies, and their cycle is broken.

Karen

These are real beasts to get rid of. Try spraying in the evening when they are home for the night too. The problems is the little buggers fly off when you spray. I had these one winter from fuchsias from a commercial greenhouse. That summer when nothing was in the greenhouse I bought a greenhouse bomb and washed the whole thing down with bleach water. I'm very picky about what goes in there but it's only 6 x 8, so nothing like you have.

I don't KNOW this, but I've read it in a few places: insecticidal soap has to be SOAP (properly so-called, soap from natural ingredients) and not detergent.

The reason given is usually that it is the fatty acids (particularly long-chain fatty acids' potassium salts) in soap that kill the bugs.

For example:
https://en.wikipedia.org/wiki/...


Detergent might or might not have fatty acids, but usually not, since there are cheaper and more powerful synthetic surfactants.

I only know to look for the word "soap" in the brand name, then read the ingredients and look for familiar names.

I asked our resident entomologist at the Extension office a few years back, and he said it didn't matter. Either soap or detergent cuts through the protective waxy coating on the bugs' bodies and kills them.