Insecticides have historically been among the first tools we’ve reached for to save crops from insect damage. But integrated pest management experts stress that these should be considered only as a last line of defense. Fortunately, now more effective ways exist to wrangle insect pests and minimize the damage they can do.
To see how these big-picture pest management practices all fit together, it helps to first understand why it’s time to step away from the spray. Turns out, when pesticides are used routinely over long periods of time, they actually give problem pests an advantage over the beneficial insects that prey upon them.
That’s because insecticides kill indiscriminately, and it takes longer for some insect populations to bounce back.
“Herbivores typically grow much faster than predator insects,” says Jermaine Hinds, a technical review specialist with Sustainable Agriculture Research and Education Outreach. (SARE is a USDA-funded organization hosted by the College of Agriculture and Natural Resources at the University of Maryland.)
“Predator insects are larger and they require protein, so, it’s harder to find food for them,” he says. “Meanwhile, the populations of plant-eating insects can rebound from a toxic spray event much more quickly.
“Doing that over and over again, it’s like you’re pushing the beneficial insects further back and giving the pest species a humongous head start. The pesticides inadvertently help [insect pests] to develop faster, and they often develop mutations to resist pesticides.”
But there is at least one thing crop-eating insects can’t easily get around. “Insects can’t really develop resistance to avoiding all of the predators out there,” Hinds says. That’s why attracting more of those natural predators is key. By developing a more robust ecosystem on your farm or in the garden, you can draw a wider variety of beneficial insects in greater numbers and put them to work for you.
Out & About
To get started, plan to add regular field scouting to your routine. “At least once a week, you want to get out of the truck and into the field. Take a look at your plants to see how they’re developing and see what pests or pest residues or evidence of pests may be developing,” Hinds says. “You want to do that so you can develop a relationship and a timeline of what’s happening in nature.”
In part, that means understanding when specific crops are coming in as well as which insects seem to be drawn to them and when. “You want to know what’s in your field,” Hinds says. “A lot of beneficial insects look like pests and vice versa. One of the examples I give a lot because we’re on the East Coast is the brown marmorated stink bug. It looks a lot like the spiny soldier bug, which is an important predator.”
The Mexican bean beetle, likewise, is sometimes confused with beneficial lady beetles.
(If you’re not sure just what kind of insects you have, snap some photos and send them to officials at your county or state extension office. They can help you to identify insect types as well as recommend effective pest-fighting strategies.)
As you make note of the various insects (friends and foes) you find, you should also examine their relationship to your crops and any other plants nearby.
Problems with specific insect pests are often a symptom of a greater ecological imbalance. “You want to think about why a pest is a pest and work to undermine [the pest], if you want long-term prevention,” Hinds says. “Is it because it’s a specialist on cucurbits? If your pests only go for cucurbits and there’s a huge density of cucurbits planted in one area undisturbed by any other plants, then that is screaming, ‘Hey, this is a buffet for others of my species!’ That will recruit more pests.”
By adding more plant diversity to the mix, you can help to camouflage your crops from pest insects. For instance, eggplant interplanted with crimson clover can slow the movement of pests such as flea beetles. “If that clover vegetation is there, it’s much harder to find those eggplants in between the clover,” Hinds says. “So, you’re diluting the signal of your eggplant or your cash crop.”
During past field experiments, Hinds recalls, “The early season clover vegetation gave the eggplants space to get this later-season boom. The flea beetles, by the end of May or early June, weren’t really a concern anymore, and then the plants were big enough and could kind of take off from there.”
Including a more diverse grouping of plants also helps to attract predator insects that will eat the very pests plaguing your cash crops. “If I add clover, and clover attracts three bee species and two predator species, and then I add buckwheat and that adds another four species, you can see how multiple plant species can cover for the gaps in your system,” Hinds says.
Besides interplanting specific cover crops, you might also try planting some insectary borders—areas near your fields or individual garden plots intended to attract and support insects.
“Oftentimes those border areas are where the beneficial insects go to rest and recuperate, to spend the wintertime, to lay eggs and build up and then return to the field when pests are available,” Hinds says.
Of course, what plants you decide to add and where you’ll add them depends on which beneficial insects you hope to attract, which insects you already have in your habitat, and which cash crops you intend to protect. “This is a little bit experimental, because it requires knowledge of what plants grow in your area and what insects are attracted to those plants,” Hinds says.
For specifics, check out Cover Cropping for Pollinators and Beneficial Insects and Manage Insects on Your Farm, some of the free Sustainable Agriculture Research and Education resources available.
Let’s say you want to attract the insidious flower bug. An effective predator of mites, aphids, thrips, insect eggs and more, that bug likes to lay its eggs on cowpea plants among others. “So, if you put cowpea in the field, you can be providing a reproductive host, so that they can breed there and build up their numbers and then go over, if your field is nearby, to forage, to look for pollen and look for any other insects,” Hinds says.
When these different plants will flower and go to seed should factor into your decisions, too. “You want to plan it in a way that the flowering plants are senescing and dying off around the time when your cash crop is going to need pest management or pollination services,” Hinds says. “Some of the ways that people have done that is by using a cover crop and rolling it under or by mowing it. The vegetation you leave behind can be used as well to feed the soil. You can form a nice healthy mat that a lot of ground-dwelling insects, like ground spiders, will use to get around and search for prey.”
Aside from actively choosing insectary border plants and cover crops, you should also be willing to leave some naturally weedy spots undisturbed for insects. (That doesn’t mean allowing invasive weeds to take hold and flourish. If you see purple loosestrife, Canada thistle or other aggressive weeds, yank those, since they can choke out native weeds that may attract a wider range of beneficial insects.)
Areas with lots of different native weeds give beneficial insects shelter and afford them with opportunities for mating and population build-up.
Putting It All Together
Adding organic matter to the soil and refraining from disruptive tilling will also help your crops sustain a greater degree of insect injury, since healthier soil—teeming with microbial fungi, bacteria and other forms of soil-dwelling life—means healthier plants.
“You want to create a plant-positive and pest-negative environment,” Hinds says. “So, for example, if the soil is improperly maintained with improper nutrients and poor drainage, that stresses the plants. That stressed plant is less defended, and, so, when insects attack those plants, the plants are less able to defend themselves.”
On the other hand? “Healthy soils have microorganisms, earthworms and things like that to aerate the soil or to create an overall healthier environment,” he says. “There’s going to be some pests, but you can introduce balance into the system by adding crop diversity, feeding the soil and creating that optimal environment for your cash crop, so that [plants] can tolerate some feeding or so that, if there are pests, there are beneficial insects around to deal with a lot of it.”
Hinds has seen it work time after time.
“I visited an organic farm last year,” he says. “[The farmer] said, ‘We never use pesticides.’ They had acres and acres of soybeans, and they created an ecosystem that works for them. That’s the aim of any kind of pest management plan. It’s a lot of things working together for a whole-farm regimen.”
This article originally appeared in the Sept./Oct. 2023 issue of Hobby Farms magazine.