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Red spider mites on leaf

Scouting for Harmful Insects – Market Farmers Introduction

It is estimated that there are a million or more different species of insects in the world. Each year, insects cause about a billion dollars in crop damage. So what’s lurking on your flower farm or market farm? In this bugging-out blog, we look at how to scout for harmful insects.

Different Types of Insects

There are about 30 different orders of insects and not all of them are pests. There are also a few different ways of categorizing insects. For farmers, we want to concentrate on what insects eat as the major tool for discerning pest from beneficial friend.

Leaf Damage on Beans - Not insect related, caused by birds - Photo Credit - David Stillwell
Leaf Damage on Beans – Not insect related, caused by birds – Photo Credit – David Stillwell

Phytophagous – The Plant Eaters

“Phyto” means plant and “phagous” means feeding on so phytophagous means feeding on plants. Yet, as diabolical as that sounds not all plant eating insects are bad. Bees, after all, feed on nectar, and that action would be considered phytophagous. There are about a half of a million species of insects that are considered plant eaters. While the name seems to imply the impending doom of crops, it’s not quite that bad. After all, many of these plant eating insects eat only dead plants, rotten fruit, or they eat without damaging the plant, such as the nectar loving bees and butterflies.

Collecting the Clues to Crop Damage

What harmful insects leave behind is damage to plants. Market farmers see this in a variety of ways and those clues often help us identify the insect, even if we do not find the culprit. Yet, not all damage to plants is caused by insects. In the case of the green beans pictured above the leaf decimation is not the handiwork of insects. Instead, this damage is caused by birds. The lesson here is that spraying insecticides is not going to stop the damage to this plant. So as Market gardeners and flower farmers consider pest control means, it is first important to accurately identify when scouting for harmful insects, or the the true pest.

The damage caused by insects can look as detrimental as the damage to these bean plant leaves. Usually, there are other clues such as eggs, poop, casings, webs, and even the insect itself. People who are not familiar with insects and their methods tend to see only the damage to the plant. One of the first ways that market farmers and market gardeners can learn how to scout insect damage is to look for other clues.

Kale with Murgantia histrionica the Harliquin bug - Photo Credit - David Stillwell
Kale with Murgantia histrionica the harlequin bug – Photo Credit – David Stillwell

Stink Bugs Damage Kale

What we see on this kale is the pest and the damage that it causes. If we were to scout around this plant we would also find eggs, poop, and other telling signs that stink bugs leave. These are true pests and the damage they do is significant. We also see that these insects are displaying warning colors. Brightly colored insects are telling you beware. In the case of Murganita histrionica – they are advertising to birds that they taste nasty. This is one reason they are so brazen about being in the open. Not many things eat them.

So, scouting for pests means looking beyond plant damage for additional clues.

Identifying Pests

Insect orders are defined by specific characteristics. Beetles for example always have a straight line that separates their elytra – hard wing covers. Hemiptera – true bugs almost always have a shield shape on their back. Look at the harlequin bugs in the above picture. The point being that with a little understanding you can begin to recognize general orders of insects and their damage.

Resources for Identifying insects:

There are a few resources online that you can use to help you find out which insect is eating your crops.

  1. Do a simple Google search – Insect damage to corn. The results include images that you can match to the damage on your crop. Click on a few images and someone will likely list the insect. Then just Google its name.
  2. Google the Insects description – Black and red bug on kale. Boom. There is that beautiful harlequin bug.
  3. Visit which is a comprehensive database of insects and arthropods and their guides.


David Stillwell organic gardener

David Stillwell is an organic gardener, entomologist, writer and student. David specializes in hymenoptera – bees, wasps, and ants, and the study of cecidology – Plant galls. He has a fondness for recognizing natural circles and energy webs that exist in nature — those interconnected natural systems such as food webs. As a native of Californian, David is an advocate for conservation, locally grown, and farmer’s markets.

Featured Image: Tetranychus urticae – The red spider mite and their diabolical web. Photo Credit – David Stillwell

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