Grub war collateral damage

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When grub killing chemicals are used, ripples spread and often have a negative effect on soil and many non-grub lives. As a grub eater, this sandhill crane is in the first ripple, affected by grub scarcity, grub purity, pesticide residue, etc. 

When we set out to kill grubs:

Beneficial insects are victims

All the grubs in an area come under fire when we target grubs, no matter what tactic we use. Even the good-guy beetle species suffer. Probably hundreds of beetle species dwell in the average, healthy North American garden and the great majority of these are beneficial or benign.

Other ground-dwelling predators of insects, slugs and snails are at risk when insecticides enter the soil. For instance:

  • Have you seen a firefly? You probably didn't realize that many glowworms and fireflies (161 North American species) live in the soil as youngsters, where they are voracious insect eaters... unless they are killed off by pesticides in the soil.


  • Earwigs, too, are soil-dwellers that hunt slugs and other undesirables.

Pests may increase

Harmful insects of many kinds can get out of hand when good-guy beetles, glowworms, firefly larvae and others are not around to hunt them.


  • One ladybug or ladybug larva removed from the picture can mean a lot more aphids, scale, corn borers or the like will live to breed and multiply -- since a ladybug can eat 30 to 60 of those pests per day.
  • Consider earwigs, again. Many people know earwigs after suffering an infestation of pesty, non-native earwig species. In a pesticide free, balanced environment such infestations are rare, while beneficial earwig species are present and active but low-key.
  • Some pests survive pesticide application and pass on resistance. Conditions or the pest's position or stage of growth may result in a sub-lethal dosage or the pest may have inherited resistance from a survivor in a previous generation. Numerous chemicals have become ineffective in this way, especially when used continually. That's one reason pest management strategies developed through university research teach us to apply pesticides only when pest numbers are actually high enough to cause trouble.

Soil condition is degraded

So much of what makes a soil "good" is the life in it. We should think twice before trying to reduce a soil animal population.


When grub killers put a dent in the soil animal population (not only grubs but critters such as underground insects and worms):

  • Natural aeration slows or stops. Water does not penetrate well. Lawn roots and other roots struggle or die in dry, airless soil.
  • Fertility declines, as fewer decomposers are there to release nutrients.

Larger animals that eat insects are affected


Birds are often victims of grub killer when it contaminates the insects they eat. Grubs are important bird food -- nutritious, easy-pickins for a robin. Even seed- and fruit-eating birds switch to collecting insects during nesting season in order to provide higher protein to their young. Nestlings die when adult birds bring them pesticide-laden grubs.

Scientists are registering connections between neonicotinoids (such as imidacloprid, one of the most widely-used soil-applied pesticides) and declines in frogs, toads, bats and other helpful animals.

Human lives are also affected by grub killer.


  • The effects touch not only those who apply the chemical or live in that garden but those who handle it all along the way from factory to garden center to gardener.
  • The most risk of acute symptoms come to those who handle the chemical in concentrated form, as in the package prior to spreading or dilution. The warnings are there on the package label.
  • Chronic exposure, synergy (combinations of chemicals) and local accumulation in soil and water occur, too. Some of these risks are known, others are suspected.