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What's bugging you? June 20, 2018

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Lady beetle eating aphids

A large part of Plant Health Care (PHC) is IPM, or Integrated Pest Management. What does this entail? In a strictly science-based sense it means that after evaluating all available management options, you select one or a combination of several that satisfy the outcome you desire at a cost you can afford and with the least impact on the environment.

Once a pest problem appears it is then time to evaluate your need to manage verses your desire to cause as little disruption as possible to your garden. So you alone must determine how much plant damage you can tolerate and how many bugs is too much.

The "best method" approach is an intelligent approach to problem solving. While there is no such thing as "a balance in nature," you do need to be aware that there are good guys or natural enemies in your garden as well as pollinators you just might want to save. But remember that insects such as aphids can increase their numbers dramatically, far outstripping the control capabilities of our existing natural enemies.

While there are less toxic management tools available to address plant problems, they usually only suppress pest numbers and do not eliminate the problem. But this may be all that is needed. There are biological pesticides such as Bacillus thuringiensis that affect only certain caterpillars and no other insects or wildlife. There are species specific Insect Growth Regulators (IGR) that prevent developing insects from becoming adults.

Sometimes the use of fertilizers can cause outbreaks of pests such as aphids. And the synthetic pyrethroid insecticides such as Permethrin, while very effective against a broad spectrum of insect pests, can cause outbreaks of aphids and spider mites.

When I need to spray for insects or weeds, I use targeted applications, rarely broadcast spraying. This minimizes drift problems from herbicides and may leave untreated areas where natural enemies are left unmolested. Horticultural oils are another option for smothering insect eggs as they overwinter on deciduous trees and shrubs.

One approach I rarely support is the release of lab reared or field collected beneficial insects. Lady beetles are a popular option but rarely stay where you release them. You might consider purchasing green lacewing eggs. You probably would have more luck with this release than others.

Now biocontrol of weeds, especially introduced exotic weeds is another story. The Colorado Department of Agriculture Insectary in Palisade is a source of several weed control agents. They presently are rearing both a mite and a moth caterpillar for Field Bindweed control. For Puncturevine (Goathead) they have both seed and stem weevils. Many, but not all of the biocontrol agents they are rearing can be purchased, but may only be available at certain times of the year. They can be ordered from the insectary by calling toll free at (866) 324-2963. Also visit their website, www.palisadeinsectary.com for more information.

The overall benefit of the PHC approach and even more specifically the IPM approach is that we can often use effective alternatives to the more toxic pesticides and we are more aware of the interaction of all the elements in our landscapes which in turn allows us to cause less disruption in our gardens. Maintaining our gardens does not always require a heavy hand but it also doesn't mean we have to go totally organic if that is not our goal.

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.

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Jim Leser, What's Bugging You
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