Integrated Weed Management
Integrated weed control has been talked about for years. Only recently has it become common to combine mechanical, chemical and biological controls to combat invasive weeds. These tactics can be combined successfully. However, there are limitations to integrating these methods. It just takes a little understanding of the weed, the insect and the best times to spray.
Herbicide application usually does not kill the bio-control insects outright. However, if one's herbicide application burns off the top of the weed, if the quality of the weed significantly declines, the insect will either have to move to unsprayed plants or perish!
The best information on integrating herbicides with insects has come from scientific studies. On a case by case basis we have learned which insects and herbicides can be used together. Studies have shown that integrating herbicides with weed-feeding insects can enhance weed control in certain cases. In most situations, the timing of herbicide applications can be adjusted so not to disrupt the mating/egg laying/feeding of the insect. Frequently, fall applications have proven to be the least disruptive to the life history of the beneficial insect.
Before going out to spray where your bio-controls are present, check out the literature (BCW would be happy to send you reprints from those studies). Armed with the right knowledge, you can safely combine control tactics and not disrupt your population of beneficial insects.
Biological Control of Weeds, Inc.
1418 Maple Drive Bozeman, MT 59715