Margaret Lauterbach

While targeting destructive creatures, don’t make beneficial insects collateral damage

Praying mantises are regarded as destructive because they can kill honeybees, but gardeners think they’re beneficial because they eat other insects, such as grasshoppers and earwigs.
Praying mantises are regarded as destructive because they can kill honeybees, but gardeners think they’re beneficial because they eat other insects, such as grasshoppers and earwigs. AP file

In our area of gardening, we’re not invaded by Japanese beetles, thanks to the efforts of the Idaho State Department of Agriculture scientists, who trapped and sprayed in specific areas for six years to get rid of that introduced pest. But we do have other insects and destructive creatures that are difficult to control.

Defining destructive creatures is a problem in some cases because earwigs, for instance, are regarded as beneficial by entomologists because they consume aphids. Gardeners regard them as enemies because they eat holes in leaves and invade fruit. Praying mantises are regarded as destructive by experts because they can and do kill honeybees, but gardeners think they’re beneficial because they eat other insects, such as grasshoppers and earwigs.

One thing gardeners should keep in mind is the fact that most insects are harmless. Learn to identify the destructive creatures, and leave the rest alone. The nondestructive insects might be helping more than you realize. I have ants in my garden, but they’ve done no harm, so I make no attempt to control them. They are turning over soil particles, making my soil looser and more friable.

There are several ways to control destructive insects: another creature eating them (ladybug or lacewing larvae, for instance); another creature parasitizing them; washing them off plants with a strong jet of water (aphids); trapping them (earwigs); withholding or not planting their preferred food; hand-picking them and dropping them into a bucket of soapy water (mature squash bugs); turning chickens or ducks loose to consume insects and slugs (they’ll probably nail some beneficial insects, too); or if all else fails, some pesticide. Using IPM, we should use only the least toxic pesticide.

Neem-based pesticides have been deemed a proper organic control in this country because it doesn’t kill honeybees, but Europe has recently banned its use after finding it killed bumblebees. Insects sprayed with Neem don’t simply keel over dead, but they get confused about eating, and die. Some pesticides kill only caterpillars (Bacillus thuringiensis or BT), but most kill many different insects. Some liquid pesticides must touch the insect, and after drying out are no longer effective. Other toxic substances such as pesticide dusts or Diatomaceous earth (DE) just lie in wait for an insect to get into it. Those pesticides can and do kill bees and other beneficial insects.

Some folks think that if they apply such pesticides in evening, after bees have retired for the day, then they won’t kill bees. But dusts and DE will be available to kill anything in the morning and for as long as it remains on foliage. Also, bees do not confine their explorations to flowers. I see them every day on nonflowering plant on foliage.

There is a lot of misinformation on Facebook gardening forums, and gardeners just have to figure out which people are giving good information. Many advise using aspirin, not advised by any experts. Many advise lavish use of “dish soap” such as Dawn. Dawn is a detergent, and not all plants survive contact with detergents. True soap is Fels Naphtha or Dr. Bronner, usually available in laundry soap sections of the supermarket. They are usually bars, so to use them, shave slices with a potato peeler and dissolve them in water for spray use. Or use Safer’s soap spray.

Some pesticides are identified as “botanicals,” meaning they’re derived from plants, but they could be as toxic or even more toxic than some made of manufactured chemicals. If you want to garden organically, at least watch for the OMRI (Organic Materials Review Institute) “seal of approval” on pesticides, and follow IPM guidelines enumerated in my column last week. Gardeners must always obey the instructions on pesticide labels for their own protection.

Send garden questions to melauter@cableone.net or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.

  Comments