Fungus Gnats

Lee Poulsen
Thu, 31 Mar 2011 16:20:38 PDT
On Mar 30, 2011, at 8:09 PM, Kelly O'Neill wrote:

>   I believe BT is a great solution. I know B. t. i. is recommended. Gnatrol may be 
> the best. Instead I used a product called Thuricide which contained B. t. k. 
> (where the k is something like kuraski) as it was more readily available to me. I 
> think it works very well. It is not quick, so the H2O2 type ideas might be a good 
> way to knock down a serious existing problem. A few days later, I'd start the BT 
> approach.
>   My unresearched approach:  I think of the BT as a living critter that I need to 
> get growing in the soil. Once I drench the soil it takes time for the BT to multiply 
> until my soil is basically immune to the Gnats. Adult flies may continue to be 
> present in small amounts but if they lay eggs, they are feeding the BT in the soil. 
> If I have any unused moist soil sitting around, I give it a shot of the BT drench so 
> the BT can start growing in the soil. I, of course, hit new plantings with some 
> also. I try not to kill the BT with harsh chemicals or severe drought. In the always 
> pretty warm conditions the Gnats thrive in, this seems to work well for me. 

I read Kelly's email yesterday, and then almost in answer to her comment about her unresearched approach, I saw the following excerpt in HortIdeas today.

--Lee Poulsen
Pasadena, California, USA - USDA Zone 10a

Bacillus thuringiensis That Works Again and Again and ...

The following is excerpted from “Getting Closer to Better Biocontrol
for Garden Pests,” by Dennis O’Brien, first published
in the March 2011 issue of Agricultural Research, from the
U.S.D.A.’s Agricultural Research Service (ARS).

ARS scientists are moving closer to developing an environmentally
friendly bacteria-based biocontrol agent that
offers long-lasting protection against caterpillars and other
pests in a garden or cultivated field.

Bacillus thuringiensis (Bt) is now used to control gypsy
moths, tent caterpillars, leaf rollers, canker worms, and other
pests that attack garden plants, corn, and other crops.
But the commonly used strain, B. thuringiensis kurstaki,
doesn’t survive more than one generation. After an initial
round of pests is killed, the biocontrol dies out and the
pests return.

Michael Blackburn [phone 301-504-9396], an entomologist
at the Invasive Insect Biocontrol and Behavior Laboratory
in Beltsville, Maryland, has been searching among the
3,500 characterized Bt strains in the ARS Beltsville Bacterial
Collection for a strain that will not only kill an initial
generation of pests, but will also survive to kill later generations.

Blackburn and his colleagues are classifying strains in
the collection based on the compounds the bacteria metabolize
and produce. As part of that effort, they tested 50 strains
of Bt known to be toxic to gypsy moths, including kurstaki,
and found that they could be divided into two groups: those
that produce an enzyme called “urease” and those that
don’t. They fed the 50 strains to gypsy moth larvae, and
when those caterpillars died, they ground them up and
applied them to pellets of artificial diet. Then they fed the
pellets to another cycle of caterpillars.

The researchers looked at survival rates of the bacteria
over several generations of caterpillars and found that the
urease-producing phenotypes survived better when repeatedly
fed to gypsy moths....

The results, published in Biological Control, bring scientists
a step closer to finding a Bt strain that will be more
effective at combating gypsy moths and possibly other insect
pests. The efforts should also lead to the discovery of
Bt strains with other desirable traits, such as the ability to
grow on mulch, multiply on specific crops, or thrive in
gardens and other sites favored by a targeted pest.

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