Insects: Which ones are truly pests?
Insects appear to be eating a plant. What are they? Oh well, might as well shoot first and ask questions later, right? Wrong! There is a logical approach to insect pest management, which includes identifying the insect, understanding its feeding habits and life history, then realistically assessing the amount of damage and whether it is acceptable or not before taking further action. This is the integrated pest management (IPM) approach and it works on weeds, insects, animals, and plant diseases. It is an ecological approach to population management that considers the presence of predators, beneficial and benign organisms (non-target organisms), people, and the environment.
Only 1 percent of insects are actually considered agricultural/horticultural pests. The rest are minding their own business, pollenating, breaking down organic matter, or eating other insects. In the United States, the number of described insect species is approximately 91,000 and it is estimated that an additional 73,000 are yet to be named. And, just because we named them, we still may not completely understand their feeding habits, life history, and geographic range. As you may have guessed by now, identifying insects is not always easy.
Recently, aphids have been colonizing a wide range of plants in the Prescott area. Ladybird beetles (ladybugs) have responded by directly feeding on the aphids and laying eggs so their predacious larvae can feed on the aphids too. Of course, there is a "lag phase" between the aphid's colonizing the host plant and the ladybird beetles arriving and building up their population. If serious damage were occurring to an edible plant (e.g. 50 percent damaged), insecticidal soap could have been applied as a contact insecticide to reduce aphid numbers without leaving a toxic residue. Newly arriving ladybird beetles would not be harmed by dried soap sprays and would lay eggs if aphids were an available food source for their larvae.
Many people plant butterfly gardens - they are very popular. Some of these folks do not realize that half the recommended plants for butterfly gardens are food for butterfly larvae: also called caterpillars. So, when uninitiated butterfly gardeners see caterpillars, they spray them because they are "attacking" the plants. Oops, no more butterflies. This happens more often than you might think.
There are appropriate times to apply pesticides. This should always be after the pest has been identified and its habits and life cycle are researched. When a damage threshold is approached, apply cultural practices, mechanical control, and watch for natural enemies of the pest. If the problem persists, I would recommend "least toxic pesticides" to begin with. Please note that least toxic pesticides that are labeled as natural or organic are not necessarily harmless to humans or the environment. Many are quite safe to use. Some have hazards associated with them. Examples include: insecticidal soap, neem oil, Bacillus thuringiensis, diatomaceous earth, and boric acid.
Need help identifying an insect or plant damage and looking for solutions? Bring a sample to the University of Arizona Cooperative Extension office at 840 Rodeo Dr #C on the Prescott Rodeo Grounds and speak with a Master Gardener. The office is open Monday through Friday, 9 a.m. to noon and 1 to 4 p.m. Yavapai County Master Gardeners have had training and experience in insect identification, damage diagnosis and they can make management recommendations when warranted. Finally, learn to appreciate insects. They perform many beneficial services for human beings.
Jeff Schalau has been the Agriculture and Natural Resources Agent with the University of Arizona Cooperative Extension, Yavapai County since 1999.