Holes In The Leaves Of Your Plants? Common Causes & Fixes

Common Causes & Fixes For Holes In The Leaves Of Plants

Holes in the leaves of plants are not the first sight you want to see in the morning, or any time. It pays to do a little sleuthing to determine not only what is eating your plants, but whether you should do anything about it. 

Vigilance in the garden is important in heading off any disease, insect, or wildlife activity. Regularly inspecting your garden plants for damage and/or pests and learning about common pest activity will keep you one step ahead of the garden marauders.  

How to Diagnose Leaf Damage

When you discover plant leaves have holes, assess the damage. Are the leaves ragged with large pieces missing? Do the leaves look like lace or are there distinct tiny holes in the leaves of plants? Can you see tunnels meandering across the leaves? Or are there slimy tracks afoot? Do the stems have a slanted cut across the top? Lift the leaves and examine the underside for tiny, soft bodied insects crowded together or caterpillars busy munching.  Often, just comparing the feeding injury with the type of pests common to that particular plant will supply the answer. 

What Causes Holes in Plant Leaves?

“Why do my plants have holes in the leaves,” is a question we often hear from gardeners. Insects, wildlife, and disease can cause holes in leaves. Often, shot-hole disease is mistaken for insect activity. Caused by a bacterium-fungus that attacks primarily fruit trees and ornamental cherry trees, the diseased spots eventually fall out, leaving a shot-hole appearance. Healthy trees generally can tolerate this disease so no intervention is needed, other than picking up and removing dead leaves. 

Common Leaf-Eating Insects and Slugs

Leaf-eating insects such as beetles, earwigs, grasshoppers, and caterpillars, as well as slugs,  have chewing mouthparts. 

Beetles, such as Japanese beetles, feed between leaf veins leaving a lacy or skeletonized appearance on the leaves.

Earwigs favor herbs, vegetable fruits, and leafy vegetables. They often leave ragged looking edges. They also provide a beneficial component by consuming aphids, caterpillars, mites, maggots. 

Grasshoppers feed on leaves, stems, flowers, fruits, and seed heads. Grasshoppers leave irregular holes within the leaf or on leaf edges. As their numbers build up, their damage can be extensive. 

Caterpillars make random holes, often on leaf edges. You can see their droppings, or frass, on the leaves.

Slugs are not insects but are in the mollusk family. Slugs are easy to identify because they leave shiny trails across the leaves that sparkle in the sun. They favor shady areas and feed on low-lying vegetation and decaying matter. Their damage is recognized by clipped off plant parts or smooth-edged holes in leaves or in maturing vegetable fruits that touch the ground.   

Insects that have piercing-sucking mouthparts feed by inserting a microscopic straw into the plant and sucking out nutrients and plant juices, leaving behind yellow spots. Common offenders include: 

Aphids, which are small, soft-bodied insects that gather on the undersides of leaves, usually line up around the mid-vein. They leave a sticky residue that attracts ants and also sooty mold.    

Whiteflies are tiny, white-winged insects that feed in groups. They flutter up when disturbed. 

Squash bugs lay bronze-colored eggs in clusters on leaves. The gray, soft-bodied nymphs feed first. Adults are hard-bodied insects that move around on the leaves, rather than staying in one place. 

Leaf-mining Damage

A common sight on plant leaves are tan blotches that wind across a leaf. Those are made by leaf miners, which are fly larvae that feed on the inside of leaves. The fly lays its eggs on top of the leaf, and the larva tunnels inside to feed. 

How to Treat Holes in Leaves By Insects

During your inspections, if you notice the holes don’t seem to be getting bigger or more frequent, chalk it off to a passing bug or wind damage. But, if the feeding damage intensifies, you may want to take action, which can be as simple as picking off offenders such as beetles or squash bugs and dropping them in soapy water. A blast of water can reduce aphids and whiteflies. Lightweight row covers can exclude beetles, moths and butterflies that might lay caterpillar eggs on vegetable seedlings. You also can let nature take its course by allowing natural predators, such as ladybugs, wolf spiders, lacewings, and parasitic wasps, to reduce the pest population. 

If you decide to use insecticides, Bacillus thuringiensis (Bt), neem oil (azadarachtin) or spinosad, which are derived from natural ingredients, can be effective against beetles or caterpillars. For soft-bodied insects such as aphids or whiteflies, try insecticidal soap, Neem oil, or other horticultural oils. Spray at dusk when pollinators are least active.

Damage by Wildlife

Leaf and stem damage at high levels are often due to deer browsing. Large pieces of vegetation are missing or entire plants, such as hosta, are consumed. Deer tracks are typically evident. Tall fencing, 6 to 8 feet (1.8 to 2.4 m) is normally recommended to keep deer out. 

Damage at lower levels is often due to rabbits, squirrels, voles, woodchucks, and chipmunks. Specific fencing or repellents often can help.