Gnats

[TBoble]

Charlie,

I have several of your plants inside.  I have a serious problem with those pesky little black gnats.  I was told that a large drop of dish soap in water would take care of this issue.  If this is correct are there types of soap that should be avoided.  I currently have Dawn with bleach and just could not bring myself to use it.  I didn't know if the anti bacterial soaps were better.  The plants are very healthy I just hate those nasty little flying bugs.  Thank you for all your advice, help and encouragement.  You guys are the best! 

[Drew]

Hello there.....

I've had what sounds to be similar little flying bastards in my house too.  I don't grow my Hibiscus indoors, but still have little flying black things.  I found that if I placed a small ramiken (kitchen stores, 3-4 oz size) half filled with wine (cheap is fine!  LOL, the little bugs don't seem to care about quality!) placed around my houseplants attracts the little guys. They land to drink and (I assume) the acid in the wine kills them.   I also add about a teaspoon of white granulated sugar to each little pot.  I change mine out about every 3 days until I no longer see the bugs flying around.  I only need the wine treatment twice a year.  Hope this works.

*****PLEASE NOTE******  I do NOT spay this on the plants or apply to the soil.  This is only to trap and kill the gnats.

GOOD LUCK!!!!

Drew in Fallbrook CA

[Cindy]

Hi Theresa and Drew,

I've never tried wine!  I have too many pets though, and I'm afraid they would drink it. But you're right, Theresa, you should avoid some detergents. One small bottle of the cheapest, plainest hand soap or dish detergent you can find will last for a year or two. It's the detergent itself that kills the gnats, and that small amount of detergent is good for the soil too. I've had 20-year-old houseplants (giant trees!) that I've used detergent on for all those years. It keeps several kinds of bugs from moving in from outside.

Cindy

[Charlie]

Just to be technical about it, these "gnats" that buzz around houseplants and greenhouse plants can be shore flies or fungus gnats. Shore flies look like small houseflies and are relatively harmless, feeding mostly on algae that often grows on the surface of wet potting mix. Fungus gnats look and fly more like mosquitoes, and they can be very detrimental to host plants. Shore flies are stockier than fungus gnats, and have shorter legs and antennae than fungus gnats. Shore flies can be a nuisance but if you think you have fungus gnats it is important to get rid of them asap.

Fungus gnats are attracted to wet potting mix that has a lot of organic matter in it. If you see them it tells you that your potting mix is staying too wet. if you can let the surface dry between waterings you won't see gnats or flies because they lay their eggs in wet soil and the larvae need the moisture to survive.

Fungus gnats feed on young roots and tender stems and are known to spread fungus diseases as well. You do not want them chewing on your prize hibiscus! I suspect that many of the disease problems we see in hibiscus are caused by fungus gnat larvae.

I've seen Cindy's home remedy work on our houseplants. It is not surprising because insecticidal soaps are well known to be effective against many insect pests when sprayed on them, so if it also works in soil on soil-borne pests that is not a surprise. Many soaps are potassium based (pot-ash) and potassium is good for hibiscus. My only caution would be not to overdo it thinking "if some is good, more is better". That often leads to problems.

In the greenhouse, we use a product named Gnatrol against fungus gnat larvae. It is a special bacteria called Bacillus thuringiensis that is eaten by the larvae. They immediately stop feeding and die soon after. Two or three treatments over a week are usually completely effective at getting rid of the problem. Adults don't live long but if you want to get rid of them while treating for the larvae you can spray the plants and top of the soil mix with pesticides such as Orthene or Bayers-3-in-1.

Thanks for asking this question. I think we will write an editorial for a future HVH newsletter on this topic!

Best of luck,

Charlie

[TBoble]

Charlie,

I must have the most persistant gnats around.  I have followed your instructions and added a drop of Joy soap in each and every watering.  I still have them.  I have even bought the sticky mouse traps and placed them in the pot next to the stock.  That catches a lot of the gnats but of course is not killing the problem.  Any more ideas?

Teresa Boble

[Charlie]

Hi Teresa,

An existing infestation of fungus gnats can be hard to get rid of with just soap. It is best used as a preventive and to stop the first stages of an infestation. A more powerful tool is to water the pots with a special type of bacteria that kills the developing larvae in the pots before they become gnats. Check out the article on fungus gnats and shoreflies that is now in the advice column of the HVH home page http://www.hiddenvalleyhibiscus.com/

We offer one product that has these special bacteria, called Mosquito Bits, on this page of the store http://www.hiddenvalleynaturearts.com/acatalog/mosquitobitsinfo.html

Please note that this is for fungus gnats, not shore flies. If you have shore flies neither the soap or the Bits will work. To get rid of shore flies spray the plants and surface of the soil with Bayers 3-in-1 every few days until they are gone. They feed on algae so if you have any algae in the pots or around them clean it up for best results.

Good luck!

[TBoble]

Charlie,

I have finally been able to make progress with those pesky gnats.  The 3-in-1 seems to be doing the trick.  I have used it as a spray on the soil and in the water for regular watering.  Another tip my mother and I use is the sticky mouse traps.  This definitely does nothing to get rid of them permanently, but you do catch a lot of them so they are not all over the house.

Thanks Charlie for the advice and help.
Teresa Boble

[Charlie]

Hi teresa,

Thanks for the sticky trap suggestion. You can actually buy sticky cards or even rolls of sticky paper that is intended to trap insects. It is a good way for a nursery owner to monitor what types of bugs are flying about and also a good way to eliminate at least some of them. Drew's suggestion about wine in cups is somewhat similar and should also help eliminate them.

The Bayers 3 in 1 will get some of them, for sure, but the shore flies have the ability to shed water and can often avoid the pesticide. Getting rid of any algae and conditions that promote algae (constantly wet surfaces) will help cut down on the shore flies, too. The flies lay their eggs on the surface of the soil where algae is present and by spraying the soil surface you are probably eliminating a big source of the problem.

Charlie