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What's Bugging Your Garden? The Caterpillars (Moths or Butterflies)

What’s Bugging Your Garden 

The Caterpillars (Moths or Butterflies) 

These really destructive garden pests are the larvae of moths or butterflies.  Generally, they go through four stages—egg, larva, pupa, and adult moth or butterfly.  The larva, or caterpillar, stage is the most troublesome for gardeners.  After hatching from eggs, caterpillars feed almost continuously on vegetables until they enter a dormant pupal state.  All adults have wings.

Cabbage loopers are pale green 1/12 inch long caterpillars that are sometimes called measuring worms because they fold into a loop and then stretch to full length as they crawl.  They chew irregular holes in the leaves of many vegetables.  The adult, an inch long, brown-gray moth, emerges in the Spring and lays single eggs on the upper surface of leaves.  The eggs hatch in about two weeks on the vegetables, and four or more generations may appear in a single year.  It is found throughout the United States and Canada.

 cabbage looper   

Cabbage looper     Photo courtesy 

Corn earworms (also called tomato fruitworms) are without a doubt a corn lover’s nightmare.  This 2 inch long green to brown caterpillar seems to insist on boring into the plumpest corn ears, where it feeds on the kernels.  After feeding for about a month, it drops to the ground and tunnels several inches into the earth to pupate.  Adults emerge in about two weeks as green to brown moths.  Unfortunately, each female moth can lay as many as 3000 eggs.  Besides corn, this pest also attacks beans, lettuce, potatoes, tomatoes, and other vegetables.  The earworm is found everywhere in the United States and Canada, but infestations are especially severe in the South.

 Corn earworm 

Corn earworm      Photo courtesy 

The Imported Cabbage Worm attacks all members of the cabbage family, including Brussels sprouts, cabbage, cauliflower, collards, kale, and radishes as well as lettuce.  This 1 inch long green caterpillar chews the outer leaves and tunnels inside cabbage and cauliflower heads.  They pupate in cocoons suspended from plants and in garden refuse.  The white cabbage butterfly with black spotted wings then emerges in early spring.  The females lay several hundred eggs underneath the leaves, which hatch in less than a week into caterpillars.  The imported cabbage worm is found throughout the United States and Canada.

Cutworms (and their close relatives, army worms) are 1 ½ to 2 inches long, smooth, dull gray to black in color, and are usually found just under the surface of the soil during the day.  At night they feed on the plants near the soil surface or crawl up the plant to feed on foliage.  You know cutworms are working in your garden when you find stems of your favorite vegetables cut off at the ground level.  This pest spends the winter as a naked pupa in the soil, and the adult emerges in the early spring.  The female lays 60 or more eggs in patches on leaves, tree trunks, and brush.  In a few days, the eggs hatch into worms ready to go on the attack.  The cutworm is found worldwide.


Cutworm      Photo courtesy 

Garden webworms, working under the protection of their own silken coverings, chomp on the stems, leaves, and fruits of beans, corn, cowpeas, peas, soybeans, and other plants.  This pale green caterpillar grows to about 1 inch long and then spends the winter in the pupal stage in the soil.  In the spring the small buff-colored females lay clusters of eggs on the leaves.  Caterpillars hatch in a week, spin a web shelter, and feed for a month.  The garden webworm is found throughout the United States and Canada.

 Garden webworms

Garden Webworm    Photo courtesy 

The ferocious-looking tomato hornworm always looks as if it’s ready to attack any gardener who dares come too close.  Even though this 3 to 4 inch green caterpillar has a horn projecting from its hind end, it is harmless:  it cannot sting or bite.  It does, however, chew big hunks out of the foliage of tomatoes, eggplant, peppers, potatoes, and related vegetables.  If left alone, it will sometimes strip the plant bare of leaves.  This pest spends the winter underground in a brown hard-shelled spindle-draped case.  Large moths with 5 inch wingspans emerge in early summer and lay single yellow-green eggs on the underside of leaves.  They are found throughout the United States and Canada.   This is one pest that is easy to spot and remove.  I’ve never found more than 2 on a tomato plant.

 tomato hornworm

Tomato hornworm    Photo courtesy 

Miscellaneous Chewing Insects 

These are neither beetles nor caterpillars, but they can sometimes be just as destructive.

Earwigs are ugly night feeding insects with a pair of pincers (forceps) at the rear end of their abdomens.  They feed on leaves at night and then hide in the soil and other dark places during the day.

Grasshoppers don’t usually attack vegetable gardens, but when they do they can be especially destructive.  Those found in gardens are 1 to 2 ½ inches long and are usually dark gray, green, brown, or black.  The female buries her eggs about 1 inch below the soil line.  Grasshoppers are found throughout the United States and Canada.

Slugs and snails can be a terrible nuisance in the home garden by devouring young shoots and seedlings and chewing large round holes in leaves near the ground.  These pests feed at night and on cool, overcast days, but they tend to hide on warm, sunny days.  You can always tell when they are invading your garden by the telltale trail of silvery slime they leave everywhere they go.  Slugs and snails attack many kinds of vegetables and are found almost everywhere.

A way to repel grubs and slugs is to place a few slices of cucumbers in a small aluminum pie pan.  The chemicals in the cucumber react with the aluminum and give off a scent undetectable to humans, but drive garden pests crazy.  You can also set out a saucer of beer and that attracts snails and slugs.  They crawl in and drown in the beer.

To trap earwigs, roll up a newspaper, put a rubber band around it to hold it together and lay it on the ground near your plants.  Earwigs like dark places and will go inside.  Pick up and destroy the newspaper, then replace with a new one.

Check your plants often.  If you have an infestation that you can’t seem to keep up with, use organic chemical methods.  Here are a few that are not harmful to good bugs, humans, or pets.

Organic Insecticides 

Sharpshooter is a citric acid in spray form that destroys the wax coating of the insect’s respiratory system.  Biodegradable.   Use for beetles, caterpillars, cutworms, earwigs, loopers,. Moths, snails and slugs.

Safer Brand 3-in-1 Ready to Use Garden Spray  targets leaf-feeding beetles and caterpillars, earwigs, and other insects.

Slugo Plus biodegrades into fertilizer.  Kills slugs, cutworms, earwigs, and snails.

Neem Oil (100%) disrupts insect’s hormonal systems, kills them slowly.  Kills leaf-eaters.

Control Leaf  Chewing worms (insect larvae) with Bt.  Controls caterpillers and gypsy moths, cabbage looper, tomato hornworms, etc.

The next blog:  Sucking Insects. 

© Copyright by Karen Newcomb