Eco-Friendly Garden Pest Control: 6 Ways to Reduce Pest Damage Without Spraying
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If you’re in the business of growing food at home without using dangerous chemicals, you’re probably familiar with natural pesticides like Neem oil, Spinosad, and diatomaceous earth. It’s tempting to go straight for the sprayer and the Neem, when you find pests eating unsightly holes in your vegetable plants.
Here’s the issue, though: many natural pesticides are fairly broad-spectrum (including Neem and Spinosad). They pose risks to beneficial insects like pollinators and natural pest predators as well as the pests themselves. Another issue with those go-to natural pesticides is that they’re often not too effective, when used on their own. Many won’t keep working for very long after spraying, and a single afternoon shower will render them useless.
If you want to keep the upper hand on garden pests while growing naturally, you really need an integrated pest management approach. Having some proactive pest control strategies in place instead of just spraying or dusting is more effective, causes less collateral damage, and often means less busy work (and less expense) for the gardener.
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1. Focus on Plant Health
Many insect pests are naturally attracted to stressed plants. A sick or weak plant will actually give off pheromones (scent) that allow them to easily find it. Why? It’s just part of nature’s efficient system. Unhealthy plants serve as food for leaf-eating insects so healthy ones can continue to produce and contribute.
Some common stressors that make plants more vulnerable to pests include:
Nutrient Deficiency
Annual vegetables need a lot of nutrients to support their fast growth rate. Unless your soil is very rich in nutrients, most annuals will do best with a dose or two of a natural, slow-release fertilizer throughout the season. Having a basic soil test done is the best way to see which nutrients are plentiful in your soil already and which ones you’ll need to add.
Organic granular fertilizers take a while to release nutrients, so young plants can benefit from a boost with a nutrient-rich liquid option like fish emulsion early on. Watch for signs of deficiency, like poor growth and yellow lower leaves, and feed if necessary.
See this post for more tips on using organic fertilizers: Fertilizing Your Garden Organically: The Basics + Some Natural Fertilizer Options.
Water Stress
Soaking plants every day (overwatering) suffocates roots and prevents nutrient uptake. Not watering enough leads to drought stress, putting them in survival mode. Both will make your plants sad and more attractive to pest insects.
Once they’re established, most veggie plants do best with a deep and thorough watering once per week. You may need to water twice per week during hot, dry weather, especially if you’re growing in raised beds. Using mulch in your veggie beds does wonders to keep that soil consistently moist and reduce water stress. Mulched plants will also need watered less frequently, in dry conditions.
Environmental Stress
Things like temperature, wind, and sudden weather shifts can cause stress in annual vegetable plants. For example, warm weather crops like tomatoes may languish if it’s too chilly out, while cool-season crops such as beets or lettuce struggle with heat.
To prevent environmental stress, try to plant when the temperatures are right for what you’re growing. For example, low to mid-40s is too cold for tomatoes and peppers. Planting brassicas, root crops, and cold-hardy greens too late leads to heat stress in late spring.
These posts have some guidelines for planting your spring garden crops at the right time:
When to Transplant Spring Seedlings + Transplanting Tips to Help Them Thrive
When to Direct Sow Vegetable Seeds for Spring (and Some Sowing Tips)
Weather tends to be unpredictable, even when you plan everything carefully. If you have plants that are struggling and under pest attack due to some unseasonable weather, the situation will most likely improve when the weather does.
It’s usually little nuisance pests such as aphids and thrips that target stressed and struggling plants. In a lot of cases, treating with natural pesticides isn’t necessary for these little bugs. They’ll clear out when you make adjustments to improve the plants’ health, like fertilizing or correcting your watering routine.
Some pests, like slugs and caterpillars, will attack the healthiest plants in the world just as quickly as they’ll attack struggling ones. Plant health is still important, though, since vigorous plants can more easily outgrow the damage they take.
2. Diversify Your Garden with Companion Planting
Some plants are said to keep pests away with a strong scent that masks the smell of their target plants. Examples include herbs like thyme, lemon balm, sage, and rosemary, flowers such as marigolds, and alliums like chives and garlic.
Folks report mixed results on how well companion planting really works to directly repel pests. For me, it’s been hit or miss in that regard. Marigolds next to my tomatoes won’t prevent hornworms, but I did have far less trouble with squash vine borers when I surrounded my squash with a fortress of dill and spring onions. I’m still not sure if it was the companion planting or the oddly cool spring that threw the borers off, last year.
In any case, planting vegetables in neat, solitary rows with nothing else around is basically setting up an easy access buffet for pest insects. Whether or not their scent can thwart pests, herbs and flowers near your veggies help to diversify your little garden ecosystem.
Blooms and variety will draw in more pollinators and beneficial insects such as lightening bugs, lacewings, soldier beetles, parasitic wasps, and ladybugs. That healthy, diverse insect population will then attract more predators like spiders and birds. Having plenty of natural predators around means pests can’t just munch on your cash crops at their leisure, which can greatly reduce damages.
3. Plant Trap Crops
Another form of companion planting, trap cropping is the practice of using “sacrificial” plants that pests tend to prefer over your cash crops. Trap crops need to be planted a little ahead of the main crop to be protected. That way, they’ll be big, lush, and appetizing to pest insects as your main crop is getting started.
Some examples of useful trap crops:
-Sunflowers can attract stinkbugs and leaf-footed bugs away from your tomatoes and peppers.
-Blue Hubbard Squash, a winter squash variety in the Cucurbita maxima family, is often preferred over other types of squash by squash bugs and squash vine borers. It may also help attract cucumber beetles away from your cucumber patch.
-Marigolds are irresistible to slugs. Plant them near vulnerable crops like brassicas and pepper seedlings, and slugs will target the marigolds instead. When planting marigolds for this purpose, make sure your transplants are a pretty good size; lots of slugs can finish off tiny seedlings in one night. Larger seedlings can often survive slug attacks and go on to produce a ton of blooms.
-Nasturtiums are much-loved by aphids, flea beetles, and whiteflies. If you plant them near susceptible crops like peppers and eggplant, those pests will hit the nasturtiums harder than your food crops. Since nasturtiums have an abundance of large leaves, they tolerate pest feeding well. The leaves might get pretty hole-y, but you’ll still get lots of blooms for you and the bees to enjoy.
4. Make Your Garden Predator-Friendly
While diverse plantings attract plenty of bugs, you can take it a step further by adding other features that pest predators enjoy. For example, create a few rock or wood piles to provide hiding spots for garden snakes, toads, and lizards. These guys will patrol your garden and eat slugs, caterpillars, and more.
Bird baths and feeders will convince birds to come around more often. Mischievous songbirds will sometimes rob newly planted seed beds, but the major benefits of having them in the garden make them worth the trouble. It’s pretty easy to cover seed beds with netting, screen, or hardware cloth until the seedlings sprout.
5. Hand Pick Pests
Many larger, easy-to-spot pests can be controlled pretty efficiently by hand-picking. In fact, it often works better than any pesticide spray or dust to keep the populations down, when it comes to larger, tougher pests like slugs and beetles.
My grandpa grew lots of muscadines when I was a kid, and he dealt with the Japanese beetles by picking them off the leaves and dropping them in a can of turpentine once a day. No spraying. I use this method for aphids, too, minus the turpentine. Aphids are easy to find, since they tend to congregate on one or two leaves at a time, and it only takes a few seconds to wipe them off and squish them.
Hand picking is most effective (and much easier) if you catch the shenanigans early on, before the pest population and/or damage gets out of control. That means scouting the garden often, preferably every day. Do a walk-through and look your plants over for unwelcome insects or evidence of pest feeding.
The more you familiarize yourself with where and when pests like to hang out, the better you’ll get at hand-picking. For example, slugs feed after dark, when the sun won’t dry out their slime coating. You’ll often find stink bugs hanging out on the underside of leaves or on the shaded side of fruits, where birds are less likely to spot them.
Fun fact: Tomato hornworms will glow under black light at night, so that’s a good way to catch them eating your tomato plants. Their near-perfect camouflage makes them tough to see during the day.
6. Use Barriers Like Netting and Plant Collars
One of the most effective and low-effort pest management strategies is to block the pests’ access to your plants from the get-go. Insect netting isn’t super expensive, and it’s pretty simple to DIY a support system for it. For sturdier plants like squash, you can drape the netting right over top of them in a pinch.
Which pests will netting keep at bay? If you use fine mesh netting like this stuff, no flying insect larger than a thrips or a gnat will be able to get through. Netting works like a charm for cabbage worms and cabbage loopers, potato beetles, leafhoppers, cabbage and carrot root flies, squash bugs, squash vine borers, cucumber beetles, and more.
Tip: Make sure your netting is well-secured to the ground with boards, rocks, bricks, etc. Cabbage butterflies and other flying pests are smarter than you’d think, and they’ll find their way in if there’s an opening.
Insect netting isn’t so effective for creeping and crawling pests like slugs, earwigs, and cutworms. They always manage to slither on under, no matter how secure the netting is. If you have cutworms, they’re likely widespread throughout the garden, and those larvae are already in the soil before you cover the area.
Another maddening caterpillar who isn’t deterred by fine netting is the armyworm, the main villain in my fall vegetable garden. Like cutworms, armyworms don’t have a single host plant. They’ll eat anything, and they’ll crawl long distances looking for food. Since they’re smaller than a grain of rice right after hatching, they can easily fit through fine mesh.
I always end up having to pick armyworms off my fall cabbage and broccoli, even with netting in place. In fact, almost every year, at least one armyworm moth has the nerve to lay an egg sac directly ON my netting! This is why a multi-faceted approach is necessary when it comes to natural pest control. No single method is 100%, on its own.
The Caveat with Insect Netting
The downside to using netting is that it also blocks pollinators from doing their important work. That’s a big drawback for plants that either benefit from or require insect pollination. That’s pretty much any plant you want to get fruit from: i.e., tomatoes, peppers, beans, squash, cucumbers, and berries.
One strategy many gardeners use is to cover fruiting crops only when they’re young and most vulnerable. Then, you can remove the netting when they’re bigger, sturdier, and starting to bloom. Greens like kale and collards, heading brassicas like cabbage, and all your root crops don’t need pollination to produce. You can keep those covered year-round with no problems.
Don’t Forget to Rotate
If you’re using netting to keep pests away from your plants, you’ll need to practice some crop rotation for max effectiveness. It’s especially important for crops that don’t stay covered for the whole season.
Lots of garden pests, such as squash vine borers, cucumber beetles, potato beetles, and cabbage worms, pupate and/or overwinter in the soil right beside their host plants. The next generation of bugs will then emerge in spring to start the cycle over.
Here’s what happens: if you cover your squash while it’s small and then remove the netting to allow pollinator access, chances are a few borers will get into your mature plants later in the season. If you then plant and cover more squash (or other cucurbits) there again the next year, those borers that overwintered will hatch out underneath the netting. There, they’ll be nice and safe from predators as they go to work ruining your new plants.
Most destructive pests of annual vegetables complete their life cycle within a year or less. That means a two-year crop rotation schedule is usually enough to prevent issues when using netting. To simplify, don’t plant the same crop in the same place two years in a row. Every other year is fine. I rotate even for crops that stay covered all season, since it only takes a few bugs that slipped in unnoticed to start an infestation under the netting.
Using Collars for Ground-Dwelling Pests
Plant collars are a quick, easy, and surprisingly effective way to stop those slithery pests that can beat insect netting. You can make them from things you’ve probably already got in your house.
Collars made from cut paper towel or toilet paper rolls or the tops of plastic cups have proven about 90% effective at preventing damage from cutworms, in our garden. Cutworms are highly destructive and can cause serious seedling damage in the spring. Using collars also deters pill bugs (a.k.a. rollie polies) from gnawing on transplants during wet weather.
If you’ve had issues with cabbage root flies in your brassicas, you can also fashion flat collars out of cardboard of cheap paper plates to prevent the flies from laying eggs around your plants.
Natural pesticides definitely have a time and a place. Though they do have ripple effects, the risks are a lot lower. Sometimes, a few treatments might be necessary to avoid losing your harvest. For example, I have to use some diatomaceous earth in addition to collars and netting to keep our spring cabbage seedlings from being eaten down to nubs.
Regardless of how you deal with pests, produce grown naturally in your backyard is going to have a much smaller footprint than that from large commercial farms. Still, having a multi-faceted pest control strategy helps to keep balance in your garden’s little ecosystem, and it makes your job easier, in the process.
