Ask A Desert Gardener, August 2024
In August, during our torrid summer, it is necessary to protect our heat-stressed landscaping from invading insects and hungry animals. Using mechanical and/or chemical responses can be beneficial.
The mechanical approach includes regular visual inspections to determine what, if any, invaders by looking for damage to leaves, stems, flowers, and branches. If damage or infestation is present, the quickest way to remove unwanted visitors is to spray plants with a strong stream of water thereby flushing insects off! This works well for spittlebugs, cochineal, thrips and aphids.
If more stubborn conditions exist, add ¼ teaspoon of dishwasher detergent (Dawn) to a spray bottle and fill with water. Thoroughly wet the entire plant and these pesty insects will slide off of the plants and not climb back! Larger insects can be manually removed and discarded using a needle nose tweezer.
With serious infestation, you may want to use a chemical approach. There are two types of chemicals: plant-based and synthesized insecticides. Examples of plant-based insecticides include planting flowers that contain natural insecticides such as chrysanthemums containing pyrethrum and marigolds containing thiophene which deter “horned” tomato and tobacco caterpillars, white flies, thrips and aphids. Peppermint oil (used in plant-based insecticides) will repel ants, hornets, wasps, mosquitos and other flying insects and can be used around pool areas as well! Diatomaceous Earth (pulverized silicon dioxide) sprinkled under organic mulch and around the perimeter of your home will kill beetles, spiders, mosquitos, crickets, ants, cockroaches, and scorpions. Neem oil (crushed neem tree seeds) can be applied to plants. It will kill insects and nematodes by altering their ability to eat and to lay eggs.
There are two categories of manufactured insecticides: Contact and Systemic. Contacts are sprayed directly on plants for immediate results whereas Systemics (containing either imidacloprid or bifenthrin) are mixed into the soil and absorbed through the plant roots in the same manner as a “vaccine”. When an insect eats a treated plant, it will die.
Systemics, however, should NOT be used on edible or fruiting plants since the foods will contain traces of the insecticide.
Have a question? Contact me at: Theplantwhisperer28@gmail.com
Howard Galin is a University of Nevada certified Master Gardener and the Chair of the SCA Garden Club House Call Program