The Effect of Pesticides on Beneficial Insects

Pesticide EffectYour industrious Planet Natural Blogger has been reading up on beneficial insects lately for a project he’s doing and has been reminded of several things. First of all, how important the role of beneficial insects is; yes to the organic gardener with pest problems but also to the environment at large. Secondly — and sadly — the effect of pesticides on predatory and parasitic insects. Now it’s not as if we need reminding of that last fact. But it underscores the extent of the consequences pesticide applications carry. And it calls to mind the balance, both the one naturally occurring in the environment and the one organic gardeners try to establish in their garden by introducing beneficial insects when called for.

Many beneficial insects — lady beetles, spined soldier bugs, minute pirate bugs; even praying mantis in some areas — exist naturally and are frequently spotted by gardeners. Others — predatory mites, trichogramma wasps — are present but harder to spot, their number increasing only in response to pest infestations. It’s important that all gardeners learn to identify them, so as not to confuse them with insects that harm your plants. When your neighbor sprays his garden because he’s spotted the larvae of the green lacewing on his pepper plants or a cluster of parasitic wasp eggs on his tomatoes and thinks it’s a sign of damage, he’s creating an opening for aphids which can harm his plants. By destroying beneficial insects, we upset the balance that nature intended.

It’s no secret that many of our major pest plagues, especially among non-native insects, have come since the introduction of arsenic-based pesticides in the 20th century and the introduction and wide use of DDT beginning in the 1950s (no need to go into the threat those concoctions held for humans here). Of course, we’ve always had plagues of grasshoppers in the American West but even the most sophisticated pesticides have failed to stop those. And then, of course, there’s the issue of resistance. The more pesticides are used, the more likely the bad insects develop resistance. Pesticide-resistant GMO crops have only made this worse.

The use of chemical pesticides has other, often hidden results in addition to killing “good bugs” that help keep pests in balance. Beneficial nematodes that attack and kill pests in the ground are also killed. The very soil microbes that help prevent disease and make it easier for plants to utilize nitrogen and other nutrients are destroyed. And we all know what pesticides have done to our bee populations and other necessary insects. Then there’s the ironic example of the leafminer which is protected from pesticide applications in the tunnels it burrows through plant leaves while its enemy, the leafminer predator, is exterminated.

Informed organic gardeners know that shunning chemical pesticides does more than protect our friends and loved ones from their harmful effects. It also helps keep the micro-environment of our yards and gardens, in balance. Introducing beneficials into your garden to control harmful insect populations is really just a means of restoring balance (in a greenhouse or indoor garden, where conditions are strictly controlled, their introduction can be most effective against insect invaders such as mites and white fly). “Restoring balance” isn’t just some trite, throw-away term. It’s an actual process that organic gardeners constantly engage in; when they improve soil, when they plant heirloom seed, when the shun the use of chemical fertilizers, pesticides and herbicides. Beneficial, predatory insects play an important role in that balance.

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