Planting green proves pragmatic for IPM

Pest management is one of the most pernicious problems faced by farmers, thanks to the fact that we are not alone in what we consider to be delicious and nutritious. Bugs, slugs and mice think our fields have been grown as an all-you-can-eat buffets just for them, and defending crops against their bottomless appetites can be a never- ending battle.

As in battle, many farmers look for the most powerful weapons to come out on top – namely toxic pest control chemicals.

But according to Penn State researcher John Tooker, escalation is not necessarily an effective strategy. Many farmers may be surprised to find out that their most productive tool for pest control might be to stick to what they know best: cultivation.

“My goal is to convince some of you that cover crops have a broader utility than perhaps some people recognize,” said Tooker, “and I’ll do that in relation to insects and crop pests.”

According to his research, a no-till approach that puts cover crops in the rotation improves pest control by building biodiversity. By creating habitat for natural predators, the farmer puts in the work up front to get the crops in the ground, but after that, they can let the resulting ecosystem take the wheel, with pronounced benefits for their yields.

“No-till is the first step in conservation agriculture,” Tooker said, noting that Pennsylvanians take pride in farming a largely no-till state. He underscored his point with a picture of a flooded field whose topsoil is rushing away in the water – inconvenient for anyone on the road but devastating for soil health.

The key to reversing this trend is building a diverse habitat in the fields, which requires a “less is more” approach. When you refrain from tilling, you allow natural predators to contribute to pest control, and as predators increase, the amount of feeding damage goes down.

This is the foundational principle of integrated pest management (IPM), a combination of biological, cultural and chemical tactics to control pest populations, which Tooker referred to as a “Goldilocks approach” to getting pest management just right.

Its key principles include avoiding preventative pesticides, which implies there’s a problem all the time. From there it follows that you have to make sure you know what’s actually in the fields, as far as predators go, and compare pest populations to economic thresholds. Then, you control pest populations only if they exceed the economic threshold. It’s important to be intentional with pesticide use.

Since 2008, slugs have shown to be the biggest problem predator, and the most common frustration for growers. “You gotta respect slugs,” Tooker said ruefully, noting how seemingly indestructible these oozing appetites are once they’ve infiltrated your fields, regardless of whatever quantities of insecticides you torpedo them with.

As he stated, “You have to remember that they are not insects, they are mollusks, and they don’t do things the same way.”

There are other aspects to the question of insecticides’ strategic deficiencies, though you wouldn’t know it based on the staggering volume of insecticides being used. According to the data, every year since 1959, when IPM was first developed, insecticide use has gone up – there’s not a single year without a rise in use. Though insecticides are more toxic than ever before, and therefore, presumably, more effective, studies on neonicotinoid seed treatments indicate that the productivity of crops with or without neonics is more or less the same.

Killing other pests with insecticides can increase slug populations, which aren’t affected by the treatments and are only too happy to fill whatever vacuum was left by insects.

Here’s where cover crops come in. Ongoing research has been showing that if you have a diverse rotation with cover crops, it increases the natural predators that will target pests and leave your crops to their growing. In studies comparing a simple twoyear corn-soybean rotation with six-year rotations with cover crops, alfalfa, corn and small grains, pests are demonstrably worse in the first category.

Cover crops help build predator populations in part because they’re providing habitat that extends the growing season. Planting green – the practice of sowing cash crops into living cover crops – is beginning to yield positive results in the research for pest prevention as well as soil erosion. As a natural suppression of weed growth, it also saves money on herbicide.

In a three-year study on planting green, an experiment with three different planting approaches – bare, brown and green – showed that the bare patch had the most slugs and the green patch the fewest. Tooker’s conclusion from the body of research undertaken by his institute is that pairing cover crops with IPM is the most effective approach to pest control.

Beyond the question of yield, Tooker demonstrated that IPM ultimately benefits farmers’ bottom line. The labor going into cover crops will be offset by the free labor that natural predators will contribute on behalf of the crops, to say nothing of the decreased cost of insecticides and the labor of their application.

If there’s a downside to using cover crops as part of an IPM approach, there exists no data to prove it.

by Holly Devon