By Erin Marissa Russell
How many times have you stepped outside in the morning to admire your garden only to discover a favorite plant has been chomped and gobbled by caterpillars? More often than not, you can find the guilty party napping in the shade of the remaining foliage, stuffed and drowsy after its feast. Although gardeners often accept caterpillars damaging their plants as an unavoidable nuisance that comes with the territory, in reality there’s lots you can do to put a stop to these tiny yet ravenous garden pests.
If you’re not sure how to identify caterpillar damage, you should know it’s time to search your plants for these wiggly villains whenever you see irregularly shaped holes with ragged edges in a plant’s foliage. Caterpillars that aren’t napping on the surface of the soil can often be found on the top or undersides of leaves or creeping along the plant’s stem, unless they’ve already fled the scene of the crime.
While established plants can usually survive a substantial amount of caterpillar consumption, their greedy feeding is most dangerous for seedlings and young plants, which they can finish off completely. Caterpillars are also particularly troublesome in the vegetable garden, where the holes they leave behind after ravaging a lettuce bed, head of cabbage, or any type of leafy greens can render the harvested plant practically worthless.
Each one of the tips below is a proven method for stopping caterpillars in their tracks so you never have to mourn the obliteration of a favorite plant again. Don’t simply accept these garden vandals as inevitable—try a few of the techniques we describe here that appeal most to you, and your garden will be caterpillar-proof in no time.
Option #1: Manually remove and execute the offending caterpillars.
When you’re able to find the caterpillars that have been doing damage to your plants, take the opportunity to make sure they won’t be back. Simply throwing the caterpillar as far as your arm can send it may seem less cruel, but it doesn’t do much to stop these greedy gluttons from returning to do it all over again tomorrow. The no-fuss method for exterminating caterpillars is to simply squash them. However, you can also bring a bucket or bowl of soapy water with you to the garden and drop in all the caterpillars you’re able to apprehend.
You should pull off and discard any rolled or webbed leaves from your plants while you’re at it, as these leaves often hide caterpillars. While this method definitively puts an end to the threat associated with the individual caterpillars you’re able to catch, it doesn’t work against their friends and family, and the task can be quite time consuming. Additionally, more squeamish individuals are often averse to taking an approach that’s quite so up close and personal with the offending bugs.
Option #2: Go on the defensive against caterpillars with insect barrier fabrics.
Caterpillars can’t munch holes in your plants if they aren’t able to reach them, and insect barrier fabrics are designed to keep these pests at arm’s length from your plants. These fabrics not only keep caterpillars at bay in their larval form—they get the job done by preventing moths from ever gaining access to your plants, so they are unable to lay their eggs in your garden in the first place. While insect barrier fabrics should be avoided if you’re growing a crop that requires pollination, they can be used during the fall growing season for vegetables, when the edible portion of the most common crops tends to be their leaves or roots.
Option #3: Break out the Botanical Bt (Bacillus Thuringiensis) to keep caterpillars at bay.
Bacillus thuringiensis (or botanical Bt for short) is actually a type of bacteria that occurs naturally in the soil, used in the garden as organic pest control—and it’s especially effective on caterpillars when it’s applied properly. You can find botanical Bt sold under the brand names Bonide Thuricide, Crymax, DiPel Pro, Ferti-Lome DiPel Dust, Garden Safe, grubHALT!, Microbe-lift, Monterey, Natural Guard, PyGanic, Safer Caterpillar Killer, Safer Garden Dust, Southern Ag DiPel Dust, Southern Ag Thuricide, Tiger Brand, Thuricide, XenTari DF, and more.
Botanical Bt fights off caterpillars most effectively when the treatment is used while the caterpillars are young and immature. It should be applied during the evening hours, when caterpillars are out and about in the garden making meals of your plants. Make sure to coat the foliage of your plants thoroughly, so invading caterpillars will be sure to consume it. Botanical Bt is such a good option because, unlike many insecticides, it’s safe for use in areas where pets will roam, and it won’t harm the local birds, fish, pollinators and other beneficial insects, or other wildlife (with the exception of butterfly larva).
Option #4: Lure in beneficial insects to dispatch caterpillars for you.
Lots of the insects that are beneficial in the garden are predators of caterpillar, so you should do all you can to entice these bugs to stop by for repeated visits. Many insects that prey on caterpillars are pollinators as well, so one way to make sure they frequent your garden is to grow lots of the blossoming plants that attract pollinators, especially varieties that are native to your area. (Find out more about this in the U.S. Forest Service booklet “Attracting Pollinators to Your Garden Using Native Plants.”)
Cultivate a wide spectrum of flowering plants, and keep them bunched in a group together so they’re easy for pollinators to spot and provide them with a lot of the nectar and pollen they’re seeking in a one stop shop. For the best results, use flowers with lots of different colors and bloom shapes to make your garden especially attractive to beneficial insects.
Other ways to bring in crowds of bugs that will put a stop to caterpillar infestations include avoiding pesticides that would harm these insects (like many broad spectrum chemical treatments), making water available to them with a feature like a bird bath or fountain, leaving a portion of south-facing land unplanted and bare, and providing nesting spots such as a pile of tree limbs or a standing dead tree.
Option #5: Use companion planting to stave off caterpillars.
If you know the type of caterpillar you’re likely to have trouble with in your garden, you can plant species that repel that type of caterpillar. For example, gardens with lots of brassica plants may have trouble with the cabbage white caterpillar. However, growing thyme, oregano, or hyssop plants near your brassicas will keep cabbage white caterpillars away.
Option #6: Keep chickens to keep caterpillar numbers down.
Much like the parasitic insects we’ve already discussed, a flock of chickens in your yard will help curtail the caterpillar population. Chickens love to hunt and eat caterpillars, but if yours are used to being given their nutrition in the form of grain, you can chop up caterpillars and add them to the chicken feed to get them used to the new food source and entice them to start hunting. You could also choose to keep ducks or even get a hedgehog, as all these creatures will hunt and eat caterpillars.
Option #7: Erect barricades to keep your property caterpillar free.
You have lots of options when it comes to barricades that will discourage caterpillars from entering your garden. Hedges around the outside perimeter of your garden will reduce the likelihood of the moths and butterflies that lay caterpillar eggs being blown into your garden. Other barrier options include fences, garden walls, or sections of trellis.
Option #8: Use a homemade or commercial neem oil spray to deter caterpillars.
A homemade spray made with neem oil is a simple way to chase off caterpillars. However, you should know that this concoction will also kill bees, so use it only at twilight when the bees will have returned to their homes for the day. Mix two ounces of neem oil with four liters of room temperature water. Spraying this mixture on the areas of your garden where you’ve seen caterpillars will kill them by suffocation. Make sure to test the neem oil spray in a small area to make sure your plants won’t have a negative reaction before you spray it all over your garden.
Only you know for sure which of these techniques will work best in your garden. Give a few of these methods a try, and see which is your favorite way to keep caterpillars at bay.