Ignoring Pests Can Work Better Than Insecticide

If you spend a lot of effort in having a vegetable or flower garden, seeing aphids on prized plants sends most people out to their local Bunnings for conventional or organic insecticides. Using insecticides will kill prey insects like aphids that eat your plants but also predator insects such as ladybugs that feed on prey insects. It may be better just to leave the plants alone and let the predator insects do their job.

Homesteading magazine Mother Earth News' weblog makes the case that using insecticide is a bad idea in the long run as prey insects multiply quickly enough that after a few generations (for insects this can be just a few years or even months) they have built up an immunity to the insecticides. Plus, you've killed off beneficial predator insects as they have a lower reproductive rate than prey insects and are more susceptible to being wiped out by insecticides.

Another general rule is that prey reproduce better than predators. If they didn't they would go extinct. Ladybugs make it from egg to larval (predatory) stage in about 5 days from as few as 3 eggs per "nest". It takes a ladybug up to 6 weeks to reach adult (egg laying) stage. Conversely, an aphid hatches from a nest of 50-100 eggs. The aphids that hatch only take about a week to reach adulthood (and thus egg laying potential). And that disregards the fact that if the aphid female cannot find a mate it can simply clone itself (in a process known as parthogenesis) and give birth to a live juvenile copy! So I ask you, if you nuke both insect groups, which will come back quicker?

Also if you use an organic spray to kill or get rid of prey insects you are eliminating the food source for predator insects who are then much less likely to remain in your area.

It can be difficult to wait a few days for predator insects to enact while watching aphids eat your plants, but it may be the best (and least expensive) strategy to save the most plants in the long run.

The Case for Doing Nothing about Pests [Mother Earth News]


Comments

    I'm no entomologist, but if the prey reproduces better than the predators, then the predators will always have a food source, but that means you will always have bugs happy to eat your plants. The ladybug might harass the aphids, but they will never be overcome.

    "Another general rule "
    See this is the reason you can't just let the buggers go au-natural, if you only have a small plot, any looses are big losses! Also a spray that kills the predators as well as the prey is naff, try looking up ways to kill one without the other, maybe ask a professional.

      Im an agronomist and I can tell you that there are no 'selective' insecticides that can kill aphids and not kill the ladybugs or any other beneficial predator insects. James has the best solution for home gardens repellent plants are your best choice if you dont want to use insecticides.

    I have been growing a range of plants in my veggie patch. It is a raised bed and I try to follow a companion plant method. Different plants attract and repel different insects. By planting companion plants that help to repel harmful insects I have found little need to spray.

      There are various natural alternatives, one I found particularly useful involves cutting up a handful or 2 of tomato (nightshade family) leaves and soaking them in water overnight. You then add as much water and spray all over the plant. Amazingly effective

    a tablespoon of dish soap in a spray bottle of water works a treat against aphids. When the water dries it leaves little soap crystals that the aphids eat with the leaves and kills them. At least that's how it was explained to me.

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