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Whole-System Management Lets Beneficial Insects Control Pests
Looking across Dustin Williams’ fields near Souris, Manitoba, it’s hard to see his farming partners working in the fields. Look more closely at soil and plants, and you’ll see workers everywhere: ladybug beetles, lacewings, earthworms, and the scavenger insects that break down crop residues.
“As a result of no-till and rotation, my beneficial bugs have increased, and my problem insects have decreased,” says Williams. “When I look down at the ground in my fields, I always see a lot of insects. My populations of beneficial insects are healthy and stable, and they keep most pest outbreaks in check. Because of that, I rarely have to control problem insects by using insecticides.”
To ensure that insects and other soil life have the healthiest possible working environment, Williams takes a whole-system approach to managing soil and crops. He evaluates prospective management practices for their potential impact on insect populations and other outcomes.
“I weigh the cost of remediation and try to decide how bad the problem is and what would be the economic and whole-system cost if I don’t spray, for instance. I try to use low-cost options first and to have patience.”
Following are the whole-system practices Williams uses to maintain strong populations of beneficial insects.
- Leave plenty of crop residue.
Soil-residing insects depend on residue for food and for the residue-recycling process for habitat. Cereal crops provide lots of residue for the rotation.
“Because of healthy populations of earthworms and other decomposers, even the aftermath from my heaviest-residue crops like oats is broken down and decomposed by the middle of next growing season,” he says.
Williams’ crop sequence begins with rye or winter wheat.
“I grow canola after that, followed by an alternative spring cereal like oats or spring wheat,” he says. “Then I grow flax or soybeans, depending on what processes I see going on in the fields. When I grow soybeans, I grow two years of soybeans back to back. Then I’ll revert to a spring cereal and follow that with an alternative oilseed. My rotation is a cereal/oilseed rotation, with oilseeds switching between flax, canola, and soybeans.”
- Weigh impact of using herbicides and tillage.
“I choose herbicides based on their safety for the bugs,” says Williams.
By designing his diverse rotation with the intent of accomplishing “weed confusion,” he is able to minimize herbicide use and to stagger the timing of application as well as the type of chemical action. This gives insects a time frame in which to recover from any treatment they may find harmful.
“I never use soil-applied herbicide that needs to be incorporated with tillage,” he adds. “Tillage damages habitat for the bugs.”
Williams considers insect habitat when deciding which fields will receive a fall working with a Smart-Till implement. “I have started to incorporate some tillage back into my system,” he says. “I use a Smart-Till implement to break up compaction. The implement’s rotary action loosens compaction to a depth of 8 inches.”
Williams uses the implement on fields only every fourth year in the fall after a spring cereal. “The tool leaves 70% of the residue on the surface,” he says. “As a result of the soil disturbance, a volunteer crop grows, and I have a healthy cover crop going back on the land in fall.”
- Scout fields for insects.
If Williams suspects conditions are leading to an unhealthy population of problem insects, he scouts fields to see how overall insect populations are trending.
“While scouting, I watch for the beneficial insects as well as for the problem bugs,” he says. “I often find that I simply need to let the population of beneficial insects bloom and control a potential problem on their own. I certainly don’t want to destroy healthy populations of beneficial insects by applying an insecticide.”
Scouting for ladybug beetles in early summer, for instance, typically shows that their population in canola fields is strong enough to control flea beetles and aphids. “Ladybugs are hungry carnivores who eat flea beetles when weather permits populations of the ladybugs to thrive when the flea beetles become active,” says Williams.
- Provide natural habitat for diverse insects.
“I maintain natural areas in my farming system,” says Williams. “I make room for tree bluffs, for instance. So if I do have to spray with an insecticide, the recovery time for the beneficial insects is shorter because they have a place to hide.”
- Have patience.
“Sometimes a bad bug will show up, but rather than spraying, I often let the system work itself out. The situation is usually resolved by the next year,” says Williams. “I try to keep moving forward and let the system stabilize itself.”
Eye on the Future
Williams’ father, Wayne, was an early adapter of conservation tillage, starting the transition to no-till as early as the 1960s. “Because of my dad, I’ve been graced with healthy soils,” says Williams. “In the early years of transition, it took a while for my system to stabilize and for my soils to trend toward greater health. Even now, anytime I transition new land into my no-till system, I usually have an ugly year while things work themselves out.”
Increased organic matter (OM) in longtime no-till fields indicates the upward trend in soil health. The sandy loam and clay loam soils test 3.5% to 4% OM.
Improving soil quality and recycling of residue contribute to a reduced need for nitrogen (N). “While still maintaining yields, I’m able to apply about 20% less N than what my neighbors typically apply,” says Williams. “I attribute much of that to the rapid recovery of nutrients in the system.”
The soil’s moisture retention is also increased, and formerly acidic soils are shifting toward a more alkaline makeup, with pH testing in the high 6’s and low 7’s. Managing for soil quality requires a long-term view. “In my decision making, I try to think about the health of the ecosystem as a whole rather than simply focusing on a single year’s profits,” says Williams. “I’m trying to work toward securing a viable future for my family on this farm.”