What's bugging you? Oct. 26, 2016

By Jim Leser


Earlier this month, several Delta County Master Gardeners, myself included, spent the morning touring the insectary in Palisade. While I had intended to cover the second weed on the list of "10 most unwanted garden weeds" this week, a discussion about our tour was too good to pass up. Besides, it will be about weeds.

The mission of the Colorado Department of Agriculture Insectary is to develop and distribute safe and effective biological controls for non-native weed and insect pests. While the program started by addressing the Oriental fruit moth, a serious pest of Grand Valley peaches, it has since been addressing weed control exclusively.

Before I get started discussing operations and specific weed control programs, I think an explanation of what is biological control is warranted. It is the use of natural enemies (parasites, pathogens, predators or herbivores) to control insects and weeds that have been introduced to our area from foreign countries.

When a non-native plant or insect was introduced to this country, it arrived without its natural enemies that had been exerting a certain level of control. And apparently there were no known effective natural enemies of these pests in this country. The advantages of biological control is that it is safe for the environment and human health, the agents are self-propagating, leading to long term control. While these biological control agents rarely eradicate the pest plant or insect, they will often lower their numbers to acceptable levels.

Biological control is a rigorous process. Non-native natural enemies brought into this country are quarantined while scientists insure that there will be no undesirable side effects or issues. We wouldn't want these introduced natural enemies attacking our native species would we? Quarantines last at least ten years. There have been no unforeseen non-target impacts to date.

The Palisade Insectary raises a number of bio controls for research and to establish field-based insectaries where natural enemy numbers are increased for further distribution. These field insectaries are located around the state. Since most natural enemies cannot be raised in the lab in sufficient numbers, these field insectaries are extremely important. And since habitat and environmental conditions can fluctuate from year to year, there are times when there are not enough to distribute further.

Now to the list of biocontrol agents currently at the Palisade Insectary and their host weeds. Many, but not all, are available to the public for their weed control efforts. For field bindweed they have both a mite and a moth caterpillar. Diffuse and spotted knapweed has a flower weevil, while the spotted knapweed also has a root weevil. Russian knapweed has a gall midge and puncturevine (goathead) has both seed and stem weevils. Leafy spurge has a flea beetle, while Canada thistle has a rust fungus. Musk thistle has a rosette weevil that attacks it. Yellow toadflax has a moth and a stem-mining weevil, while dalmatian toadflax has the same moth but a different stem-mining weevil than the yellow toadflax.

Many, but not all of these biocontrol agents are available to you, at only certain times of the year and can be ordered from the insectary by calling toll free at 866-324-2963. Cost for these agents runs about $30 to $35. Also visit their website, www.palisadeinsectary.

com for more information.

Jim Leser retired to Cedaredge in 2007 after a career with Texas A&M University Extension in entomology. He is a member of the Cedaredge Tree Board and a Colorado Master Gardener.