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.