Invulnerable? White Flies on my Mint

This is war. Some of my Mint plants are infested with White Flies. I don't know if they're bothering the plants (My plants seemed to be doing great before I noticed the flies and still are), but I've made it my business to eradicate them. The problem is, they like it where they are and won't cooperate. I've now drenched the plants at least five times with various insecticides, all of which listed White Flies on their labels. One of the articles I read said, "As a last resort, use Pyrethum". Well, I have, and I thought that the concentrated solution I last used (Pyrethrin Garden Insect Spray) would do the job because it called for the unheard of concentration of five tablespoons per gallon. Well, it didn't work, the White flies are still gamboling around my plants. I even tried gassing them. The plants are in five-gallon plant bags. I enclosed the bags in large garbage bags and sprayed-in large quantities of a Pyrethrum spray. I then left the sealed bags over night. It didn't work. I probably killed many White Flies, but there were also many unaffected ones. What's left? The article said, "As a last resort". Does that mean that there is nothing more I can do? Do I have to surrender? Oh, I have placed some sticky yellow cards around the most infested plant. They captured many flies, but many are still left. I also purchased a yellow incandescent bulb, which is supposed to fry the flies, but I haven't tried it yet. I did try a small vacuum cleaner, but that didn't work out too well. Any ideas?

Are these plants inside or outside? I would take them outside and blast them with water to get most of the flys off before you treat with a spray. You might also try removing the 1-2" of soil and adding fresh soil. Most of their eggs are probably in that soil. The soil being constantly wet from repeated drenching is probably adding to the problem. If that doesn't work, you might try pruning off the most affected stems. Mint can usually take a heavy pruning and even thrive better in the future b/c of it.
I also wouldn't spend another dime on any more treatments since it's probably cheaper to buy a new plant and start over.

Can you post some photos of your plant?

This message was edited Sep 19, 2011 10:09 AM

I agree- whiteflies are very hard to get rid of- I would start all over.

Thanks for your comments. I would have replied before, but I've been distracted by some other problems. Anyway, a friend of mine had the same comments as you. After having the same experiences as I've had with White Flies, she finally just gave up, and stopped trying to grow whatever plant it was. That "solution" doesn't suit me. I'm going to get them. If I were a commercial grower, or even if I was growing the mint for my kitchen table, I might scrap the plants, but I guess the Captain Ahab streak in my personality won't permit this. I will persevere until I've seen the last of those little white specks or....

At this point, I'm not sure what my next step will be. Using biological controls is a subject of interest to me, and I'll probably be ordering the recommended predators or parasites. Even if that fails, it will be a learning experience. Finally, I'm sure that somewhere there is an insecticide from hell that will do the job, although using it will not be as satisfying.

I might add something that I left out before in order to avoid too long a message. When I gassed my mint plants with a Pyrethrin vapor/spray, I left the black plastic containing bag around my 5-gallon pots for too long. What happened was that the sun came out and I delayed removing the bags. The result was that my Mint plants were severely damaged by the heat. I thought I might even lose them, but although I had to remove quite a bit of dead portions of the plants, they revived remarkably. They still don't look as good as they did before then, but they are coming back strongly. Anyway, that incident got me down. The plants were gassed overnight, and the baking the next day almost killed them. Surely, I thought, that would have done in my White Flies. Wrong. They were diminished in numbers, but they were still there.

I won't be back until I get rid of the flies, so I'll just say this for now. I have discovered that there are White Flies in other kinds of plants near my Mints. There are not the clouds of White Flies that infest my Mint, but they are there. Finally, around the corner of my house I have Mint growing in a large tub. The Mint has been there for several years, but I've never seen any White Flies there.

Since I've been having a problem with white flies too, I'm wondering if you ever got rid of them. I found the buggers on several plants that I overwintered in the basement. Don't know which plant they came in on but they seemed to prefer 3 or 4 in particular. They seem to hide on the inderside of the leaves and there are some leaves that seem to draw them more them others. Then I find tiny dots that you can remove. Suppose they are eggs. On careful inspection I've noticed that there is a stage when they don't seem able to fly yet, perhaps just born, and you can pinch the leaf and kill them. Once they can fly, well, good luck!
A gardening friend had a terrible infestation outdoors last year. There were clouds of them in her gardens. It's still too early here in Minnesota to know if they will be a problem for her again. Please tell me you found a solution.

I'm still at war, but I'm going to win. I think the main thing is not to declare victory too soon. Even after you think you've gotten them all, you haven't. You just have to keep at it until you're sure that you have gotten them in all of their stages. This is the main point. Another thing that I've found useful is a poison container to which you attach your garden hose. I had thought I had given my plants good drenchings before, but when I tried a bottle with a hose attachment, I realized that I had only begun. Talk about deluges. If the poison didn't kill them, I drowned them with the flood of water.

The funny thing about it is that I see no evidence that the Whiteflies are actually hurting my plants. Here I am turning into a contemporary Captain Ahab, when I don't know if the flies are really detrimental. True, I don't want to risk inhaling them. but it may be that they aren't doing any damage, noticeable damage, anyway. So what's worse, me becoming a obsessive/compulsive slayer of Whiteflies for no good reason, or just letting the little rascals enjoy themselves? Well, I guess I'm some kind of moralist, so the Whitelies have to go.

Snorklepop, have you tried superfine oil? It's less toxic, but you do have to respray often. It basically smothers them. I also encourage the Hummingbirds, as they eat a lot of whiteflies while they're flying.

U.C. Davis has some good information and guidelines for whitefly management.
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7401.html#IDENTIFICATION

Consider the amount of poison your dumping onto the plant, do you still want to use it for culinary purposes? The poison is probably killing beneficial insects too, which throws the whole balance out of whack.
I would really just get another plant. If this started in september and they are still a problem, you clearly dont have the upper hand on them.

HydroPinke:
You're right about that, but what happened is that I gave up. I'm back now, however, and this time I'm going to stick around until I see the last of them. I think that if I drench the plants and soil once a week for a few weeks that should be the end of them. In the meantime, my plants never looked better. They looked pretty shabby a few months ago, but I now realize that it was just that time of the year. As for culinary purposes, that's not important to me. I only planted the mint to add their fragrance to the yard, but that didn't work. They smell like mint should smell, but my ten or so plants were not enough to affect the air yards away. I'm keeping them, though, because they just look nice. They add welcome greenery to the driveway. You do have to hand it to those little critters, though, they're TOUGH. I wonder if there are any other garden pests that put up as much of a fight.

Hmmm. I can think of half a dozen that are that tough, right off the top of my head.

I forgot to mention two other things that increase the chances of success: (1) Use different poisons. Everything I've read says that Whiteflies have a great capacity to develop resistance, so make it a little more difficult for them. They can't be resistant to EVERYTHING. (2) Spray surrounding plants even though they don't seem to be infected. This is where I've gone wrong before. Now, EVERYTHING gets sprayed. If you keep this up for, say, three weeks, that should be the end of those little rascals.

There are absolutely bugs that are resistant to poison. More poison in more places is not the answer, you are absolutely damaging the environment and natural balance of the ecosystem by continually dumping poison on everything. The poison is not bug specific, it kills everything. You are putting your plants at more risk for further infestations of other insects by killing off their natural predators and beneficial insects. Every bee takes that poison back to the hive when they collect the nectar from the flowers, please consider the damage you're doing to the environment. I trust u.c. Davis for horticultural information as do many others, and they outline management and control on the site I listed, it specifically says do not use excessive insecticide application to control whitefly. Please read at least the following excerpt from their guide before you continue to dump poison on EVERYTHING.


"Management of heavy whitefly infestations is very difficult. Whiteflies are not well controlled with any available insecticides. The best strategy is to prevent problems from developing in your garden to the extent possible. In many situations, natural enemies will provide adequate control of whiteflies; outbreaks may occur if natural enemies that provide biological control of whiteflies are disrupted by insecticide applications, dusty conditions, or interference by ants. Avoid or remove plants that repeatedly host high populations of whiteflies. In gardens, whitefly populations in the early stages of population development can be held down by a vigilant program of removing infested leaves, vacuuming adults, or hosing down (syringing) with water sprays. Aluminum foil or reflective mulches can repel whiteflies from vegetable gardens and sticky traps can be used to monitor or, at high levels, reduce whitefly numbers. If you choose to use insecticides, insecticidal soaps or oils such as neem oil may reduce but not eliminate populations.

Biological Control

Whiteflies have many natural enemies, and outbreaks frequently occur when these natural enemies have been disturbed or destroyed by pesticides, dust buildup, or other factors. General predators include lacewings, bigeyed bugs, and minute pirate bugs. Several small lady beetles including Clitostethus arcuatus (on ash whitefly) and scale predators such as Scymnus or Chilocorus species, and the Asian multicolored lady beetle, Harmonia axyridis, feed on whiteflies. Whiteflies have a number of naturally occurring parasites that can be very important in controlling some species. Encarsia spp. parasites are commercially available for release in greenhouse situations; however, they are not generally recommended for outdoor use because they are not well adapted for survival in temperate zones. An exception is the use of parasite releases for bayberry whitefly in citrus in southern California. You can evaluate the degree of natural parasitization in your plants by checking empty whitefly pupal cases. Those that were parasitized will have round or oval exit holes and those from which a healthy adult whitefly emerged will have a T-shaped exit hole. Whitefly nymphs can sometimes be checked for parasitization before emergence by noting a darkening in their color. However, some whitefly parasites do not turn hosts black and many whitefly nymphs that occur on ornamentals are black in their unparasitized state.

Avoiding the use of insecticides that kill natural enemies is a very important aspect of whitefly management. Products containing carbaryl, pyrethroids, diazinon or foliar sprays of imidacloprid can be particularly disruptive. Control of dust and ants, which protect whiteflies from their natural enemies, can also be important, especially in citrus or other trees.

This message was edited May 5, 2012 4:29 PM

I've seen some people in the hibiscus forum talk about top dressing the soil with worm castings as a way to control whitefly so you might try that too.