Pests & Diseases
Pests and disease are inevitable parts of gardening.
There--I said it.
There are two ways you can fight the good fight:
1) Try and eradicate it all
2) Let nature do it's thing.
Here at Kraus Farm, we choose option B. Keep reading to find out why it's worked well in our favor over the past decade, and what you can do to minimize the amount of work and effort you put into having a healthy garden.
The key to pest management
Nature provides the things we need to be successful gardeners. Ten years ago, I was the first one picking apart every plant in the garden, searching what bugs needed which sprays. It was exhausting, and it never did the trick anyway. In fact, they often came back full force.
Then I learned about balance. Everything has a predator. Some have fewer than others, but they have them. The nice thing about gardening is that usually it's an insect pest--and lucky for us, they have lots of predators. However, when we kill every bug that hits our plants, there are no prey to keep the predators around. And without predators, those pests just keep returning.
When we learn to sit back and let nature take its course, we invite the predators into a food-rich environment. They'll choose that space to lay their young and continue the cycle. Leave the bugs alone, and you'll find that within a year, they'll hardly be a problem anymore.
Every insect has a predator. Ladybugs eat aphids. Parasitoid wasps attack hornworms. Dragonflies eat mosquitoes. The key to a successful garden environment is to create a home that welcomes those predators so you can maintain balance. So here are some basic ways you can make your yard a comfortable place for them:
Stop spraying. Pesticides are not target-specific (with the exception of Bt), and so it will harm all insects that come in contact with it, even if the label only mentions specific ones. Spraying kills the predators too.
Plant for insects too. If you know you have a specific pest, research its predators and what they like to live in. This may mean native plants that host them, or a grassy area where they like to nest. In order to have the garden you want, you have to plant for insects too. Otherwise, you're attracting only the things that eat your plants. Not cool!
Leave the pests. Unless your plant is all but decimated by the bug, seeing an insect munching on your vegetables is not the end of the world. By leaving them, you invite the predators that use that pest for food. Leave them! It doesn't take long to balance out.
Stop killing bugs. Our gardens are outside, and that happens to be where bugs live. Your garden won't function well in a bubble. We can't keep killing them "just in case," even if they look scary. They carry out special and specific functions in our ecosystem and they need to stay alive in order to maintain the balance we seek. (Obvious exceptions are clear and obvious danger, like a yellow jacket nest being in front of your front door. Yikes)
Keep them happy!
If you've grown tomatoes (or eggplant or any kind of nightshade vegetable), you've probably come across one of these suckers. They can absolutely eat an entire tomato plant down to the stems, and so I am giving them their own section. Pest VIPS, these ones are.
What they are: tomato hornworms are the caterpillar larvae of a family of moths called sphinx moths (Sphingidae). They're big, about 4" long, and are distinguishable by the big horn-like spike at the end of their tail. After winter, pupae emerge and mate. The females lay the eggs on the underside of leaves. Their caterpillars are the hornworms we love to hate. Once they've eaten enough, they drop off and bury into the ground to pupate and begin the cycle again mid-summer, where the cycle continues until they stay for the winter underground.
What to do: it's instinct to want to kill these caterpillars, but they are an important part of our balanced ecosystem. Killing them disrupts the cycle only enough to detract predators and, consequently, invite more of them. Instead, remove a small branch from your plant. They like the top leaves, and those are usually the youngest anyway. The plant can survive it, and will probably be happy for a little pruning anyway. Move that branch far from your garden. We drop ours in a grassy area toward the back of our yard.
How to detect them: There are two tell-tale signs. If you wake up one morning to find a leafless area of your tomato, pepper, eggplant, or potato plant--start looking. You should notice round dark green or black droppings on the leaves that fall from above.
Prevention: there's not much you can do to prevent them since you're planting the things it likes to eat. Instead, make it a nightly habit to go out after dark with a small blacklight. They glow under the blacklight and are very easy to spot this way at night. Just remove them with a small branch and relocate them far away from where your plants are. Remove weeds to reduce the number of sites where worms can lay eggs.
Predators: birds and reptiles love hornworms. General predatory insects such as lady beetles and green lacewings often prey upon the egg stage and on young caterpillars. Another important predator is the paper wasp, Polistes spp. This common wasp feeds on many types of caterpillars including those found in gardens. But the coolest predator is Cotesia congregatus, a small braconid wasp. They are parasitoids, meaning they lay their eggs ON the hornworm and then the wasps eat the hornworm after they hatch. If you see a hornworm with rice-like eggs on its back, just carefully move it. You'll be helping the pest-predator balance!
What they are: They are small, soft-bodied insects that feed by sucking the nutrient-rich liquids out of plants. Ranging in colors all over the spectrum, you'll usually find them in large groups. They reproduce live young, but are usually slow and wingless.
What to do: nothing! Most of the time, the ladybugs and lacewings will swoop in before they have time to do any real damage. If you see visible signs of heavy damage, do not spray your plants with insecticide! Instead, use a heavy stream of water. They'll be knocked off and rarely find the same plant again. If you leave them where they are, you'll invite the predators in no time!
How to detect them: They like young growth, so you will typically find them on the underside of newer leaves in a clump like the picture to the right. If you see leaves curling under and changing color, or if they're sticky, that's a sign of visible damage. Even still, you only really need to do something if those are the only (or majority of) the leaves on the plant. Otherwise, let predator balance do the work! I've never had any kill a plant before, and I leave them.
Prevention: Aphids are especially attracted to nasturtium. Plant these near more valuable plants as traps for the aphids. The aphids will likely go for these plants before your tomatoes, but don't plant them too close so they don't eventually move on to your veggies.
Predators: Beneficial insects, such as ladybugs, lacewings, and parasitic wasps, will feed on aphids. Attract these insect to your garden by providing an environment that features a range of flowers and foliage plants, as well as access to water.
What they are: It can be so disappointing when your squash is thriving and suddenly starts to wilt. This may be the result of a squash vine borer (SVB), which is a type of moth that lays its eggs at the base of squash plants. When the eggs hatch, the larvae burrow (or “bore”) into the lower stems, weakening or killing the plant outright. They typically attack squash, zucchini, pumpkins, and various types of gourds. They overwinter in the soil, and when they emerge they lay their eggs at the base of those vines. Then the larvae bore into the stems and feed for 2-4 weeks. Lucky for us, there is typically only one generation per summer!
What to do: If you catch them VERY early, you can manually remove the squash vine borer. Locate the entry point of the larvae, then slit the stem lengthwise with a fine, sharp knife to remove the larva by hand. One plant can house several larvae. Carefully remove the larvae without doing more damage to the plant. After removal, cover the slit stem section with moist soil above the point of injury to promote formation of secondary roots. Also, extra rich soil near the vines helps rerooting. The bacteria Bacillus thuringiensis (“Bt”) is a natural insecticide that can be injected into and applied to the squash stems. It is target specific and will only harm the larvae inside.
How to detect them: You might notice that your plant's leaves are starting to wilt unexpectedly. Look for holes at the base of the plant and green or orange-yellow sawdust-like “frass,” which is the chewed up stem that the larvae produces as it burrows into the plant. The stem will start to rot at the site of the feeding first.
Prevention: Don't plant your squash in the same area two years in a row since they overwinter in the soil. Remove ALL plant debris at the end of the season. Physical barriers are your best bet once the season starts. Cover the bottom few inches of the stem with aluminum foil to prevent them from being egg-laying targets. Avoid varieties that are particularly susceptible, like Black Beauty Zucchini. Butternut squash and Cucuzzi (Lagenaria siceraria)—also known as the snake gourd—tend to be resistant to squash vine borer attacks. Or, plant "trap crops"--extra plants a bit away from your crops that are inviting to the borers. Let them eat those so they avoid trying to attack the ones you're protecting. This pest is around for only 6 to 8 weeks and can only eat so much. Finally--plant squash in late June when most are already gone. It's tempting to get an early start, and with enough preventative measures you can, but planting after they've passed through really avoids them best.
Predators: Parasitoid wasps love SVBs! They're pollinating wasps, so keep plenty of flowering plants in your yard--especially native ones. If you supply nectar sources, the beneficial wasps will find them. Water, especially during hot summer weather, is vital to all beneficial insects. You can use a shallow bowl or a birdbath with some large stones for resting places.
What they are: The adult squash bug is a flat-backed insect that’s fairly large (over 1/2-inch long). They are usually dark gray to dark brown. They are able to fly, but they often simply walk around on plants. Young squash bugs, or squash bug nymphs, are gray and have black legs. They move quickly and often congregate in groups on the undersides of leaves. Squash bugs overwinter in dead leaves, vines, under boards, and even in buildings. In early June, they'll lay eggs in clusters on the underside of leaves, but the adults usually hang out under damaged leaves or near the plant crown. These bugs inject a toxin into the plant and suck the sap right out of it with their sharp, sucking mouthparts.
What to do: Pick egg masses off the plants in the morning and later in the day. You can also simply scrape the eggs off the leaves with a butter knife and let them fall onto the ground, where beetles will eat them. Eggs hatch in about ten days, so be sure to check for them on at least a weekly basis. Or, place a board or shingle in the garden at night (or pieces of newspaper). During the night, both adults and nymphs will congregate underneath the board. Insecticides are not effective to manage squash bugs once they are adults, so don’t bother trying.
How to detect them: if you don't see them or their eggs, you'll see leaves with yellow spots that eventually turn brown where they've sucked the sap out. Eventually, those leaves will wilt and prevent the flow of nutrients to the rest. The plant will dry up and darken, turning brittle.
Prevention: Remove plant debris during the growing season to reduce sites where squash bugs can hide. Keep checking your plants, at least daily. In the fall, be sure to compost old squash vines to rid your garden of any possible shelters for breeding and over-wintering. Cover plants until flower starts using row covers.
Predators: Predatory insects including the bigeyed bug (Geocoris punctipes), Pagasa fusca and the damsel bug (Nabis sp) directly munch on the all the stages of squash bugs whereas the feather-legged fly (Trichopoda pennipes) adults parasitizes both the nymphal and adult squash bugs but adults of the scelionid wasp (Gyron pennsylvanicum) parasitizes eggs of squash bugs. The predatory bigeyed bugs are attracted to sunflowers whereas damsel bugs are attracted alfalfa, clover and radish flowers.