Controlling Insects

By Sherry Rindels-Larsen

Spring has sprung and with warmer temperatures and longer days comes welcoming new growth for our plants. Along with new plant growth, insect populations are popping too. Insects multiply rapidly and monitoring their populations is important for plant health.

Spring is the time of year we see aphids, thrips, mealybugs, spittlebugs, scale crawlers, and other soft-bodied insects. Many insects feast, or more appropriately, suck the juices out of new plant growth. When their populations grow to an unacceptable level, control of the insects is necessary.

Biological controls are always present. ese are natural predators that help control what we view as pests. Lady beetles, mantises, spiders, wasps, lacewings, and other bene cial insects will feast on aphids, mites, and thrips. Make sure you know the various lifecycle stages of the bene cial insects to avoid mistaking them for bad bugs. Nature often takes care of the pest population without our intervention, however, if the population of the pest rises above what the bene cial insects can handle, it is time to bring on the next line of defense.

One of the most e ective ways to control soft-bodied insects is hosing o the a ected plant with water. e key is targeting the water where the insects are. Many insects gather on new growth, unopened ower buds, the underside of young leaves, and developing stems. Focus the strong blast of water where the insects are, and many will be dislodged and killed. Repeat as needed.

If water alone does not do the trick, a low-toxicity alternative is an insecticidal soap. is alternative is inexpensive to use and is one of the safest to use for us as a pesticide applicator as well as for animals and birds. It is also safe for most bene cial insects. Insecticidal soaps kill by su ocation and disrupt the cellular membranes of the insect. ey remove protective waxes that cover the insect, resulting in dehydration. Soap is also helpful in removing honeydew, sooty mold, and other debris from plant leaves. ere are several commercially available insecticidal soaps available. Regardless of the brand you select, the soap must contact the insect for it to be e ective.

Years ago, it was commonly recommended to make your own insecticidal soap by mixing hand or liquid dishwashing detergent with water. Today, I caution against doing this because current concentrations, formulations, and other ingredients found in liquid detergents may be phytotoxic to sensitive plants and cause plant damage. e variable concentrated formulations make it hard to recommend a general dilution ratio that is e ective against pests without injuring the plant. If you decide to make your own, use a soap that does not contain additives and test it on a small portion of the plant to insure there is not a negative response. One tablespoon of soap to a quart of water is su cient.

Resources

Calendar of Appearance of Some Common Insects in the Sonoran Low Desert https://cals.arizona.edu/pubs/insects/ahb/ calendar.html

Citrus Mealybug https://cals.arizona.edu/crop/citrus/insects/ citrusmealy.pdf

Spittle Bugs in the Low Desert Ridge Justice Court https://cals.arizona.edu/maricopa/garden/html/t-tips/ bugs/spittle.htm

Managing Scale Insects https://cals.arizona.edu/yavapai/anr/hort/byg/ archive/managingscaleinsects.html

Aphids https://extension.arizona.edu/sites/extension.arizona. edu/ les/pubs/az1635-2014.pdf

Insecticidal Soaps For Garden Pest Control https://hgic.clemson.edu/factsheet/insecticidal-soapsfor-garden-pest-control/

Use of Insecticidal Soaps in the Low Desert https://cals.arizona.edu/maricopa/garden/html/t-tips/ bugs/insecticidal%20soap.htm

Sherry Rindels-Larsen is President of the Sonoran Desert Club and a Maricopa County Extension Master Gardener

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