Monday, August 19, 2013

How to Control Insect Pests Naturally

The EPA just approved another systemic pesticide, saying that it is needed because the pests have become immune to previous poisons.  This is a losing game, as plant-eating pests can easily outbreed the poisons, while their predators and bees cannot.  Systemic pesticides, which are distributed into every part of the plant through its roots and stems, are particularly dangerous to bees, hummingbirds, and predatory insects, which rely on nectar for fuel.

The smallest pests are inherently the hardest to control in a conventional yard or farm, yet they can be easily managed in a naturally managed landscape that makes their predators comfortable and lets them breed. 
Such pests are not pestilential all the time; it is only when they infest and become a plague that they become a real problem.  If most plants that sprout in natural conditions were able to grow to maturity, they would be too small and crowded for the good of the rest of us.  Herbivorous “pests” thin most of the plants as they grow, the smallest and weakest ones first.

An infestation of any pest is a feast for any predator that eats it.  Given a chance to do their job, predators multiply as they feast, and the population of the pest crashes back to pre-infestation levels.  In a natural landscape, any infestation is a temporary affair.  When ladybugs and soldier beetles home in on aphids on roses, they don’t last long.

Ladybug adult, credit Little Miss Parasite,

 Nearly mature ladybug larvae on my mature corn, with grey aphids, one week after ladybugs mated there.

A few days after the previous photo, the corn is cleaned of all but aphid trash.

Three things make insect predators comfortable: shelter; food; and water.  The shelter for many predators is leaf mulch; coarse bark works as well.  Adults and/or larvae crawl around under the mulch, eating whatever they can kill.  At night, many crawl out of hiding and stalk their prey on the plants.  Ground predators include soldier beetle larvae, ground beetles, ants, spiders, centipedes, and even earwigs, which eat fungus-infected leaves, not healthy plant tissue.

 Soldier beetle, credit  Ground beetle, credit

Since insects have little sugar or fat, their predators need an energy source like nectar, and many of them, like parasitic wasps and soldier beetles, prefer small flowers, the smaller the better.  Carrot flowers qualify, as do chickweed and purslane, chickweed in spring, purslane in summer.  Both of these low, spreading annuals are useful and edible, and don’t bother other plants much.  Deadhead your carrot flowers; they are likely to make half-wild seed that makes white, skinny roots.

Water is needed as well.  If you buy ladybugs or spider mite predators, it is important to water the tops of the plants so they can take a first drink.  Bees, wasps and birds mob sources of water in hot, dry weather.  Spider mites love dryness and shun humidity.  Sprinkler irrigation and misters are best for providing the water that your predators need, along with baths and fountains for birds.


  1. The aphids appeared on a few of my corn plants one week before dozens of ladybugs were seen mating there. Within another week, scores of nearly mature larvae were eating the aphids, with many younger ones as well, and a few ladybugs continuing to mate.

  2. Yesterday, I checked those plants and found nearly all the aphids were gone. There is another small group of infested plants that the ladybugs have not found yet that started last week.