Perhaps as you’ve strolled through your garden lately, you’ve looked at a plant and thought, “What’s eating you?” It can be tricky to discern what is doing the munching when the muncher is nowhere to be found. Some telltale signs paired with a little knowledge can help you sleuth out the culprits.
Start by assessing the magnitude of the damage. Whole leaves or twigs disappearing overnight is often the work of vertebrate critters like deer and rabbits. Deer damage appears like plant material has been ripped or torn off. Newly planted annuals are often pulled right out of the ground. Deer love flower buds and tender new growth. On the other hand, Rabbits leave very sharply trimmed stems cut at a nearly 45-degree angle. Once you have discerned who is doing the nibbling, you can choose fencing, repellent products, or even replace the plants with less-palatable options. For more information, see HGIC 2362, Wildlife Control.
Another culprit that could defoliate your plants is the humble caterpillar. There are many species, some of which have specific host preferences. Some caterpillars can be difficult to catch in the act, dropping to the ground at the first sign of a threat. You can often find their droppings or frass as evidence. There are two important things I’d like you to remember about caterpillars. Firstly, caterpillars eventually have an adult form. All the butterflies and moths once started as hungry caterpillars. If you value native butterflies and moths, go easy on the control methods you choose. You may accept some damage as a small price to pay now for a little winged beauty later. Secondly, there is often a biological option for caterpillar control. Limit the risk of unintended injury to other insects and beneficial bugs by choosing a targeted biological control like Bacillus thuringiensis (Bt). Bt is a microbial insecticide that affects the gut of caterpillars when they consume it. For more information on using Bt, see HGIC 2770, Less Toxic Insecticides.
Beetles are another chomping pest. They generally make irregular-shaped holes or gauges in various plant parts. Their feeding patterns vary by species and crop (like the skeletonized leaves left behind by Japanese beetles). It’s always best to identify which beetle is causing the damage before applying control measures. Our online factsheets are a great place to start when looking for pests of various plants. Keep in mind, if you see almost perfect circles cut out of leaves, you may have a leaf-cutter bee gathering nesting material.
Slugs and snails love to hang out under potted plants or in moist mulch during the day and do their chomping at night. You’ll find irregular holes and sometimes see a telltale slime trail. They are relatively easy to manage by drying out their habitat or using an iron phosphate bait. For further information, including beer bait trap instructions, see HGIC 2357, Snails and Slugs in the Garden.
Sometimes circular holes in a leaf have nothing to do with a munching critter and are caused by a disease. Various leaf spot diseases can cause leaf tissue to die and fall away, leaving a shot-hole appearance. You may notice the symptom of discolored spots on the leaves before the holes develop.
Whatever the scenario, make sure you properly identify the plant and the pest BEFORE attempting any control measures. Happy garden sleuthing!