If you’ve ever planted anything you understand the havoc that invasive insects can unleash on your garden. There’s nothing more deflating than tending a beautiful, green path of lovely edibles only to discover one day that some uninvited guest has moved in and ruined all your hard work. It’s heartbreaking.
The best thing we can do in the fight against garden pests is educate ourselves. If we can become familiar with who were dealing with, how to identify them, what they can do to our plants and how to prevent or remove them we can stay ahead of potential catastrophe. So let’s look at some of the most common garden pests and what we can do to control them.
Common Garden Pests and How to Control Them
These guys are the worst! Aphids are tiny, pear shaped insects with long antennae which cluster on particular plants in large masses. They can range in color depending on the host plant and can spread quickly. Aphids feed on plant sap and cause wilting of leaves and deformation of the host plant. They also excrete honeydew on the leaves which promotes sooty mold growth. Aphids can be found on most plants but they especially like Brassicas like kale, cabbage and broccoli.
The best way to control this invasive best is through vigilant observation and quick action. If you begin to see them, remove or wash them off the plant immediately and continue this process. Organic pest sprays, especially garlic spray, work well to control aphids. Ants are known to bring in aphids so controlling ants can help prevent aphids. Aphids to have some natural predators like lady bugs, mantids and lacewings. We’ve had really good results planting onion or garlic near our greens and brassicas to reduce aphids.
Caterpillars and Worms
Caterpillars are soft-bodied, segmented larvae with a distinct, harder head capsule with six legs in the front and fleshy false legs on rear segments. Some are very showy with bright colors and fine hairs that serve as a defense mechanism. Common caterpillars you may find in the garden are cabbage worms and loopers which love to eat holes in brassicas (cabbage, broccoli, kale), tomatoes, and cucumbers. They can be found on many fruits and vegetables, ornamentals, and shade trees. Caterpillars chew on leaves or along margins; some tunnel into fruits.
Moths and butterflies lay their eggs under the leaves of plants for protection, sometimes as single eggs or in clusters. It’s easy to catch these guys before they hatch and get rid of them by simply brushing them off the leaves or trimming the leaves with eggs off the plant. They are voracious eaters, but luckily are usually easy to spot with close inspection and easily plucked from the plant when found. Some organic sprays can deter them.
These beasties are incredibly destructive. Tomato Horn Worms are technically another type of caterpillar and can devastate a plant or group of plants in a very short amount of time. I’ve had nearly and entire basil plant or small pepper plant consumed in little more than a day by one of these revenous monsters. Their color can vary depending on diet, but they are usually a light or dark green with yellowish markings and are easily identified by the stinger-like “horn” on their tail which gives them their name. They can grow up to 4 inches long and get very fat with an insatiable appetite.
These guys will usually start to show up in late spring. Check the plants often, inspecting under leaves and along stems where they can grab on with their powerful grip. The best way to get rid of Horn Worms is simply to remove them by hand when you see them. Again, some sprays work and they can be taken out when young if there are predators around. A full grown, fat and angry Horn Worm can be intimidating but you gotta just get in there and remove them as soon as possible.
White flies are often found clustered under broad leaves. We most commonly find them in our garden among the aphids under older kale or cabbage leaves. Like aphids they consume sap and literally suck the life out of the plant through the leaves which can expose the overall plant to other issues by weakening it’s health.
They can be convinced to move on (though not far) with a strong spray of water from the hose. Light detergent (or soapy) water can damage their wings and keep them from flying around, eventually killing them. Other organic sprays can work as well. Once found infesting a plant, it’s best to remove the affected leaves. White flies are attracted to yellow. Sticky, yellow fly traps can attract them and capture them. You can also paint the inside of a bright yellow bucket with some sticky stuff (Vaseline or resin) and place near your garden.
More of an annoyance than anything else, Leaf Miners are larvae that feed between the upper and lower surfaces of leaves. Identified by the tell-tale random patterns left on the affected leaves, the damage is mostly cosmetic. Heavy infestations can hinder plant health but this would be rare. Various types of leafminers attack various kinds of plants. They’re found on broadleaf trees as well as shrubs and bushes. Leafminers are a major cause of poor harvest numbers in home gardens as they weaken individual vegetable plants. They’re especially fond of spinach leaves and their tunneling severely decreases the attractiveness and value of the crop.
Keeping your plants as healthy as possible will limit the opportunity for leafminers to infest your garden. Since leafminers are the larval stage of small flies, using sticky yellow fly traps can help by reducing the egg-laying population of adult flies. At the first sign of leafminer damage, you can also squeeze the leaf with your fingers at the leading edge of the channel killing the offender before they do much more damage.
Squash Bugs, Stink Bugs and Green Bugs
This general group of vegetable bugs represents a large set of garden invaders. They go through various stages, starting with eggs laid on the underside of leaves. They love beans, tomatoes, corn and many other green-leafy plants. The eggs hatch into colored nymphs in about 3 weeks, and the nymph’s stage is about 80 days as they change to black. The adult stage lasts for about 100 days. They can do a lot of damage as adults, piercing fruit, suck plants’ sap and damaging leaves.
The best control once the adult bugs are spotted is simply to pluck them off and crush them. Ideally, the introduction of natural predators and the eradication of eggs or larvae before the develop into adults is the best way to control them. Using a natural organic spray or neem oil early on can reduce the chance of a full blown outbreak.
There are unknown millions of mite species, many similar to thrips (another common garden pest). In the garden the two-spotted mite is commonly called red spider mite because in the cold weather it changes from pale green with two red spots to reddish rust color, looking like a miniature red spider. Like thrips, spider mites suck the chlorophyll from the leaves of plants. Spider mites leave white translucent spots of damage and no dark droppings. In heavier infestations, a silky web is secreted by the mites to protect themselves from enemies.
Natural predatory mites are the best control, so having compost and mulch to encourage beneficial mites will keep the right balance. Spiders, parasitic wasps, lady bugs and lacewings also feed on red spider mites. Use a soap spray to eradicate these critters.
THE TOP 7 GARDEN PESTS: WHAT WORKED AND WHAT DIDN’T
Mother Earth News did a survey to learn more about what works, and doesn’t, when it comes to limiting insect damage in organic vegetable gardens. They surveyed 1300 gardeners from across the United States. This includes 7 of the top garden pests and info:
1) SLUGS– took top honors as the most bothersome pest in home gardens, with 55 percent of respondents saying the slimy critters give them trouble year after year. Handpicking was highly rated as a control measure (87 percent success rate), followed by iron phosphate baits (86 percent) and diatomaceous earth (84 percent). Opinion was divided on eggshell barriers (crushed eggshells sprinkled around plants), with a 33 percent failure rate among gardeners who had tried that slug control method. An easy home remedy that received widespread support was beer traps (80 percent success rate).
2) SQUASH BUGS– had sabotaged summer and winter squash for 51 percent of respondents, and even ducks couldn’t solve a serious squash bug problem. Most gardeners reported using handpicking as their primary defense, along with cleaning up infested plants at season’s end to interrupt the squash bug life cycle. The value of companion planting for squash bug management was a point of disagreement for respondents, with 21 percent saying it’s the best control method and 34 percent saying it doesn’t help. Of the gardeners who had tried it, 79 percent said spraying neem on egg clusters and juvenile squash bugs is helpful. About 74 percent of row cover users found them useful in managing squash bugs.
3) APHIDS– were on the watch list of 50 percent of respondents, but the success rates of various control techniques were quite high. Active interventions, including pruning off the affected plant parts and applying insecticidal soap, were reported effective, but so were more passive methods, such as attracting beneficial insects by planting flowers and herbs. Several readers noted the ability of sweet alyssum and other flowers to attract hoverflies, which eat aphids. “We attract a lot of beneficials by planting carefree flowers in the vegetable garden, including calendula, borage, zinnias, cosmos and nasturtiums” (Midwest, more than 20 years of experience).
4) SQUASH VINE BORERS– had caused problems for 47 percent of the survey respondents. The best reported control methods were crop rotation and growing resistant varieties ofCucurbita moschata, which includes butternut squash and a few varieties of pumpkin. TheC. moschata varieties are borer-resistant because they have solid stems. Interestingly, if you’re attempting to fend off squash vine borers, lanky, long-vined, open-pollinated varieties of summer squash (zucchini and yellow crookneck, for example) may fare better than hybrids, because OP varieties are more likely to develop supplemental roots where the vines touch the ground. Many gardeners dump soil over these places, so if squash vine borers attack a plant’s main stem, the plant can keep on growing from its backup root system.
5) JAPANESE BEETLES– Forty-six percent of respondents reported working in the unwelcome company of Japanese beetles, with handpicking being the most popular control method. Some gardeners grow trap crops of raspberries or other fruits to keep Japanese beetles away from plants. Several commonly used interventions — garlic-pepper spray, milky spore disease, pheromone traps and row covers — had high failure rates.
6) TOMATO HORNWORMS– were of concern to 42 percent of our survey respondents. Bt and handpicking were the preferred control methods, and several folks commented that tomato hornworms are among the easiest garden pests to handpick (probably because they’re large, easy to spot and produce a telltale, pebbly trail). Many gardeners reported seeing tomato hornworms often covered with rice-like cocoons of parasitic braconid wasps. “I had a lot of tomato hornworms this year, but the wasps took them out! Just like in the photos online and in bug books!” (Mid-Atlantic, more than 20 years of experience). Gardeners named zinnias and borage as good companion plants for reducing hornworm problems.
7) CUTWORMS– were a concern for 41 percent of respondents, and effectiveness ratings for using rigid collars (made from plastic drinking cups or cardboard tissue rolls) to protect young seedlings from damage were amazingly high (93 percent effectiveness rating).
A common practice to reduce cutworm damage is to cultivate the soil’s surface once or twice before planting and hope robins and other bug-eating birds will swoop in to gather the juicy cutworms. Big, sturdy seedlings are naturally resistant to cutworms, so many gardeners said they set out seedlings a bit late to avoid cutworm damage.