Grow-How: Pests--Prevent, Protect, and Respect

by Isabel Vinton

It's hard enough to get plants to grow without other things trying to eat them. Every gardener knows the disappointment of seeing their precious plants munched by invading critters, and at times it can feel futile to protect your garden from the hungry insects that turn to them for food. But though natural pest control is nuanced, imperfect, and ever-changing, generations of garden guardians have trialed and tweaked their tactics to keep the joy of gardening alive. This week, learn about some common garden pests and how to protect against them.

1. Aphids: These tiny pear-shaped bugs live in large groups on the underside of leaves. They can be white, grey, red, brown, yellow, or black, and may or may not have wings. They suck the sap out of vegetable, fruit, and tree leaves, causing grave injury to the whole plant. Most gardens have some amount of aphids. Some even overwinter in the egg stage and greet spring alongside gardeners. If the population gets out of control, however, it can mean trouble for your garden.

Solution: Lacewings feed on aphids, so planting flowers that attract them is a great natural way to keep their numbers at bay. If the aphid population does get away from you,  there are organic, households mixtures (such as soapy water or a stinging nettle solution) that can be applied to kill and deter them.

2. Flea Beetles: The oversized back legs on this impressive jumper earn it its name. Flea beetles are pinhead sized and oval shaped with colors ranging from blue to green to black, sometimes with striped wings. Their favorite pastime is hopping around the garden and eating cabbages, cucumbers, eggplants, grapes, potatoes, and tomatoes. Flea beetles munch on foliage and leave it riddled with tiny holes. Their larvae, meanwhile, feed on plant roots and tubers. Flea Beetles overwinter as adults, awakening in May or June.

Solution: Putting up physical barriers like row cover in the spring makes it tough for the beetles to access young, vulnerable plants. Later in the season, brushing them off into a bucket with soapy water will help keep the population under control. Keeping weeds in check (particularly horsenettle and wild mustard) also reduces their habitat.

3. Snails and Slugs: Snails, and their shell-less counterpart the slug, might seem slow, but they waste no time wreaking havoc in the garden. Ranging in color from pale yellow to black, they feed mainly after the sun goes down, and although they prefer lettuce, they won't hesitate to taste other greens, vegetables, and flowers.

Solution: Their slimy bodies need moisture and shade to function, so reducing their habit around your plants is the first step: remove piles of old lumber or debris and keep the area weed-free and well-mowed. Picking them off individually is one of the most effective ways to reduce their garden population. Hand-harvest the slugs an hour or two after sunset, and (unless you are relocating them to a far-off slug sanctuary) throw them in a bucket of soapy water. For a hands-off alternative, set out shallow pans of beer or an empty citrus rind or large cabbage leaf, cut in half and placed upside down on the ground. These methods will attract snails and slugs. The third option is to create barriers between them and the plants. Anything sharp that may damage their soft bodies, such as crushed eggshells, gravel, or wood ash, will make slugs think twice before crossing treacherous terrain.

4. Cucumber Beetles: Infamous across North America for their damage done to cucurbits, cucumber beetles are small oval-shaped insects, yellow and black in color, striped or polka-dotted in pattern. The beetles love to feed on melons, watermelons, winter and summer squash, and, of course, cucumbers. They will also, on occasion, attack other crops such as beans, corn, and potatoes.

Solution: Control measures for cucumber beetles are the same as for flea beetles (physical barriers, removal by hand, soapy water solution, keeping weeds down), as they are for the majority of pests encountered in an organic garden. You can get to know cucumber beetles even better by reading our Bug Profile on them.

5. Tomato Hornworms: A true terror to tomato growers. Armed with a sharp horn on their  rear to use in tandem with a head thrash and clicking sound when disturbed, these giant worms have an appetite to match--although in actual fact they're not worms at all, but rather the caterpillar stage of the Five-Spotted Hawkmoth. If you're not certain about your identification of the large green caterpillars, the pattern of thin white Vs on their backs should inform you. Although they prefer tomatoes, they will eat any plants in the Solanaceous family, including potatoes, peppers, eggplants, and tobacco, and moonflower as well. Damage from hornworms can look similar to deer: branches will be completely defoliated and stems chopped off.

Solution: Picking them off by hand is effective, although they can have such a strong grip on the stem that it’s sometimes easier to just snip the branch right above where the pest is sitting. Then either remove them to a remote location, put them in a bucket of soapy water, or squish them. To learn more about hornworms and how to encourage their natural predators, read our Tomato Hornworm Bug Profile.

6. Japanese Beetles: These iridescent copper and green beetles are generally active in the Northeast in July. In the larval stage, they are gray or white grubs with brown heads, often crescent shaped, and commonly found living in (and feeding on) plant roots, particularly grasses. Although corn, tomatoes, and beans are among their favorite foods, they have been found to have an appetite for over 200 cultivated ornamentals and edibles. The effect they have on plants is often called "skeletonizing," since they eat foliage and leave only stems and veins. They also munch on flowers and fruit. And not only do they physically damage the plant, they can also cause open wounds that are vulnerable to infection.

Solution: Tansies, Rue, Garlic, chives, and catnip are said to deter the beetles. Border your garden with these plants to cut down on beetle traffic. Row cover with edges thoroughly sealed to the ground can keep plants at a safe distance from beetles. Although pheromone-filled traps do exist, we do not recommend them. Studies have show they actually attract more beetles than they can catch. If you do get an infestation, the best solution is to pick them off by hand and either squish them or drown them in soapy water, either as larvae or adults. This is best done early in the morning, when they are wet with dew and unable to fly quickly. You can also spread a cloth under the plant that the beetles have occupied, then shake onto the cloth, gather up, and dispose of them. Get the full scoop on Japanese Beetles here.

7. Small Mammals: Squirrels, mice, and chipmunks can make a snack out of a whole seedling. They also like to dig newly planted seeds out of the soil and eat them. Woodchucks and rabbits can be even more destructive, nibbling down whole crops before you know it. Some gardeners may opt for traps (either lethal or otherwise), but many people prefer cruelty-free methods.

Solution:  Planting strong-smelling herbs like mint, or alliums like garlic, leeks, and onions, around your garden has been shown to deter rodents, as have sprays of cayenne pepper and water. As with insects, make sure to keep anything they might interpret as good real estate far away from your garden, including wood piles, pet food, sheds, bird feeders, tall grass, garbage, and compost. Even mulch can make them feel right at home. Another option is to physically block them from your garden. Row cover won't be as effective here since rodents can chew straight through it, but wire tunnels, raised beds with mesh or wire at the bottom, or enclosed gardens (though beware of gaps around gates) can all provide a safe haven for your plants. There are also many testimonials of scattering chunks of Irish Spring Soap around the garden as an effective deterrent.

8. Deer: Perhaps the most infamous garden eaters of all, there is practically nothing a deer won't chow down on. Although gardeners are always asking for deer-resistant varieties to plant, the sad truth is that there are very few things that are guaranteed to be safe. Thought deer didn't like tomato plants? See the photo to the right and think again! So if we accept that your plants are probably at risk for deer, what can we do to protect them?

Solution: Some people find that pungent-smelling plants like lavender, catmint, or alliums; fuzzy or hair ones like lamb's ears, yarrow, or nicotiana; or thorny ones like roses can deter deer. However, like people, deer have different tastes, and some may find these perfectly acceptable meals. Some plants, like daffodils and poppies, can also be toxic to them.  Again, reducing habitat is key. Deer prefer areas that offer quick cover in the case of predators, so eliminating that cover will discourage deer from hanging out in your yard. The best option, of course, is a fence at least eight feet tall. However, since this isn't an option for everyone, other forms of barriers exist, like hedges or taut strings of fishing line. Barriers with two layers of wire or fencing can befuddle their sense of depth perception. For some added fun, install a motion-activated sprinkler to scare them off. You can also always put cages or netting around specific plants you want to protect--this method can also work against birds. Chances are you'll have to experiment with a combination of methods to keep deer away.

There are a lot of overlaps in natural pest control: reducing habitat like weeds or compost, creating physical barriers like fences or row cover, and using deterrents like soap are common themes. Always be sure to harvest produce as soon as it's ripe or a little before, since pests will be watching for that perfect ripeness too. Additionally, if you're thinking of getting chickens, cats, or dogs, now might be the time, as they'll help with insects, rodents, and deer respectively.

Although our short-term approach to pest control for insects is simple and unpleasant (squish them by hand, ideally while they are still in their egg phase), the long-term goal is to help the garden become a balanced ecosystem where good bugs eat bad bugs, for example. The alternative, most often, is either a lost harvest or a garden full of chemicals. It's also important to remember that everything we call a pest has a role to play in the ecosystem, even though they can be invasive or overpopulated. The tomato hornworm, for instance, metamorphoses into a sphinx moth which pollinates flowers. Every gardener has a different comfort level with eradicating pests through methods like squishing and trapping. Striking that balance between your garden and the greater natural world is the honored task of every grower.