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Try not to kill the good insects

Try not to kill the good insects

  • Updated

Gardeners tend to have a low tolerance for insect pests. It’s understandable. We work hard to cultivate healthy plants. Seeing them ravaged by insect infestation is frustrating.

But, grabbing insecticide and spraying at will can do more damage – killing beneficial insects and doing harm to the environment – and may not even address the original problem if the chemical was not intended for the pest targeted (and especially if insects did not cause the problem in the first place).

So, first off, be sure you know whether it is an insect causing the problem and, if so, which one.

We need to know what insects are on our plants and whether they are friend or foe. Many insects are beneficial to the garden. Some are pollinators. Some actually prey on pests, handling pest control for us. The hover fly (syrphid fly) is both. A pollinator as an adult, in its larval form, it eats aphids. That’s my kind of insect.

Next, assess the damage to determine the need for control. Is it really that bad? And, does it outweigh benefits? Butterfly milkweed, for example, will be very chewed up by the end of summer, but it’s worth it when you can watch pretty monarch caterpillars and anticipate their adult stage. When white-lined sphinx moth larva chewed up my pentas, I was thrilled to have provided a host plant and to eventually see adult sphinx moths take up the pollinating night shift. The rather unattractive caterpillars chewing up foliage on coneflower, aster and sunflower will become silvery checkerspot butterflies.

If damage is unacceptable and control truly is needed, determine the best course from a range of options. Spraying chemicals can (and should) be the last choice.

Some insects can simply be removed by hand – I’ve plucked many a tobacco budworm off my petunias. And I’ve been known to just prune out an insect-infested branch or stem and dispose of an entire group of pests at once.

If chemicals are used, be sure to follow label instructions and warnings.

Looking at the big picture, though – before identification, before control – providing the right space, moisture and light for plants to grow strong will limit issues with pests.

Have a variety of plants instead of just a few species; it will limit the ability of insects to move through plants and inflict damage. Many insects are specific to certain plants and will not affect others nearby.

Make sure plants have enough space for air circulation and that they have the proper amount of water; it will encourage healthy plants capable of withstanding insect pests.

Remove debris, such as fallen leaves; it will eliminate areas pests are likely to live.

Taking steps to prevent insect problems in the first place is the least harmful option, for pollinators, other beneficial insects and – ultimately – for us.

Mari Lane Gewecke is a Master Gardener volunteer, affiliated with the University of Nebraska-Lincoln campus program, and a self-employed consultant.


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