I have about 20-30 houseplants in my small 1 bedroom apartment. Although I wouldn't say it's severe, I have a small pesticide problem. I have little fungus gnats and some whiteflies around several of my plants. When in past times I've sprayed with an all purpose houseplant insecticide, some of my plants leaves turned yellow and then died. Plus the insects simply left that plant and went to another. It seems the majority of the bugs prefer plants that are kept moist, or that have just been watered. I've also tried to mist with a diluted dishwash soap and water. But I'll admit I have not stuck to a consistent routine. With my hardier plants like Pothos and Peperomia, I brought the plants outside till the bugs died. Does anyone have any further tips on what I can do to completely eliminate the pest problem before my little apartment and all my plants are severely infested?! Please help! Yesterday, I misted almost every single one of my plants with an houseplant insecticide. What further things can I do to ensure I will eliminate these pests!
I'd make sure first that you're not watering too much--even plants that enjoy a lot of water might do better with a little less. I've never had trouble with fungus gnats except when I was watering too much. To control them, I've seen people suggest a few different things--yellow sticky traps, watering with hydrogen peroxide (only when the plant actually needs to be watered though!) and Bt (Bacillus thuringiensis, the stuff that mosquito dunks have in it) to take care of the larvae in the soil.
Go to a good local garden center and buy "Mosquito dunks". Put one quarter of one in your watering can. This has BT in it, safe for human and pets. It will kill the larvae in the soil. Use sticky traps for the flying adults. Give the Dunks time to kill off the larvae and you'll see a big difference. Also let the soil surface of your plants dry out a bit between waterings.
Fungus gnats plague my houseplants every couple of years, despite that I don't overwater. I control them with Sticky Stiks, which are yellow sticky papers that are attached to little plastic stakes that you put in each plant. The gnats are attracted to them and get stuck when they land. I've tried just about everything and find that these work the best. You can buy them at garden centres and hardware stores. Good luck!
The sticky traps sound like a good method for your small area.
You can also use a bread bag and a lure. Fold down an empty bread bag just a bit. Stand it in the area and use a banana peel or something similar to draw the gnats into the bag. Once they are inside, seal it shut and toss.
I too have had a problem with the little black gnats but I dont know if they were fungus gnats or what because they were all over! I do believe it was from watering but I have since repotted all my plants except for three into clay pots and that made a big difference.
I am an Interior Plantscaper, and we have problems with the fungus gnats @ least two times a year: spring and fall, when they hatch, and b/c our plants are in businesses, we cannot use pesticides, so the one thing we have found that works beautifully is red wine. Buy some red wine, pour a little into a small cup or container that will fit into your plant, it attracts them, they drown and die. Now, if you cannot fit a cup into your plant, just set it behind or as close to the plant as possible, but if you CAN get it into the plant do that first. Pretty sure it's the tannins in the wine that attract them. We have also used the sticky traps which work well, too. We will also use a product called Gnatrol, which is a larvaecide, and it seems to help a lot. Now, before we install a new plant into an account, we remove the top 2" of soil, if possible, some plants don't allow this b/c of how thick and dense their roots are but this helps remove any larvae that are in the soil. They say when they lay their eggs they will lay them within the top 2-4" of soil, then we use the Gnatrol to kill any more that might be deeper in the soil. The wine works the best, for us, and keeping our plants on the drier side helps a lot.
I had a problem with fungus gnats in the plants I have on my office desk. The high-end potting soil I used to transplant and re-pot all of my plants was infested and the larvae immediately started hatching (boy was I ticked). After fighting with them for a couple of weeks (and being pretty limited on what I could use, since it is an office and everyone is allergic to something or another), I re-potted my plants again and added a half inch or so of crushed granite to the bottom of each of the pots, as well as a quarter to half inch on top of the soil. The gnats are now completely gone (they disappeared within days), and I believe the larvae are dead. It has been about a month now. I am considering removing the granite from the top of the soil to find out for sure. So far this seems to be an effective way to deal with the issue without having to use soaps or pesticides, or sticky traps.