Good and bad bugs of the garden

5 min readAug 4, 2020

Joe Malmisur, Interpretive Naturalist

Part 1: “Bad Bugs”

Now that it is officially summer, your garden should be well on its way to producing lettuce, peas, beet greens and maybe even some beans if you got them in early. Broccoli should be heading, as well as cabbage. Tomatoes and peppers should begin to blossom soon, if they haven’t already. Weeds are growing faster than you can pull them and you are beginning to see some disturbing signs on the leaves, stems and fruit: insect damage! You might also be experiencing damage from fungus, blights and virus. No, COVID-19 is not making your plants sick, but cucumber mosaic virus could be the culprit, among several others.

You may be asking yourself: What do I do next, and where do I begin? What is eating holes in my bean leaves? What is eating entire parts of the broccoli and cabbage? Why are the ends of my vines dying? Why does my plant look droopy? I have watered it religiously. So many questions. I am really getting frustrated! All this work and look what is happening!

Breathe and relax. Let’s begin by identifying what you are seeing that is causing the damage, i.e., “the bad bugs.” Then in a follow-up blog post, we will identify the “good” bugs and how to promote their populations so they can eat the ones causing most of the damage.

The following list makes up the top 10 garden pests in Ohio (in no order), their favorite host plants and the damage they cause that you are likely to encounter this summer.

Cucumber Beetles

Damage is done by adults as the plant emerges from the ground.
Adults move to the fruit and chew pits and holes.
Transmits cucumber bacterial wilt and cucumber mosaic virus.
Host plants are cucumbers, melons and squash.

Squash Vine Borer

Pupa overwinter in garden debris and hatch mid-spring.
Adults lay eggs in the soil; larva then burrow into the base of the plant or vines of squash, zucchini and pumpkins causing the vine to wither and die.

Cabbage Worm

This is the larva of the cabbage white butterfly
They feed on leaves of plants in the cabbage family.
Can completely skeletonize the plant very quickly.
Host plants are cabbage, broccoli and Brussels sprouts.
Up to eight generations per year are possible.

Bean Leaf Beetle

There are over 1,500 leaf beetles and most are serious pests of the garden and field.
Adults feed on leaves and fruit; larva feed on roots, leaves and fruit.
Host plants are green beans, cabbage, broccoli and radish.

Colorado Potato Beetles

Adult and larva chew leaves.
Can strip a plant of foliage quickly.
They’re the biggest threat to potato crops worldwide.
Host plants are potato and eggplant.

Asparagus Beetles

Adults chew pits in emerging spears of asparagus.
Larva chew the fern-like leaves causing stunted growth.
Populations can explode causing plants to wither and die.
Host plant is asparagus.

Corn Earworm

The larva of a moth, the earworm burrows into the ear of the corn eating kernels and leaving a trail of frass (droppings) inside the husks of individual ears.
Considered the most destructive pest of both field and sweet corn in the United States.

Aphids

There are about 1,351 species of aphids currently recorded in the United States and Canada, of which about 80 species are pests of the garden.
Aphids are slow moving and come in shades of green, red, brown, black and yellow.
Aphids can affect all garden plants. They have needlelike mouthparts which they use to suck juices out of plants and excrete excess sugars as “honeydew.”
Aphids do not chew, but large numbers can cause plants to wilt and die.

Root Maggots

These small, white to yellowish grubs are the larva of several different flies.
Eggs are laid in the soil; they hatch and burrow into root crops such as carrots, onions, radish and turnips leading to disfigurement and bacterial infections to the crop.
Some species of larva also feed on young roots causing the plants to wither and die.

Flea Beetles

These smallest of the leaf beetles are a metallic blue-black in color.
Adults do the most damage by eating small holes in the leaves.
Populations can explode and cause damage quickly leading to stunted growth or dead plants.
Host plants include broccoli, cabbage, kale and eggplant.

Now that we know what bugs we are dealing with, we can develop a comprehensive IPM (Integrated Pest Management) plan. In our follow-up post, we will learn how to encourage “good” bugs as well as other strategies to help in controlling the “bad” bugs from doing too much damage. It will be helpful to review the families of insects and types of metamorphosis prior to reading this next part. Enjoy the heat of the summer and the fruits of your labor!