Cutworm pressure may have eased in some areas over the past two seasons, but farmers should not be caught off guard when conditions favour another outbreak. Recent experience has shown that the pest can cause costly damage to maize and, to a lesser extent, soybeans and sunflowers.
For farmers, the message is clear: cutworm control should start before planting, rather than after damage appears.
According to Syngenta insecticide specialist Gustav Venter, some serious outbreaks in recent years have occurred in areas where farmers have adopted no-till or minimum-tillage systems. While these practices offer important soil-health benefits, crop residues, weeds and soil clods can create shelter and food sources for cutworm larvae.
“The most effective non-chemical preventative measure is to keep the field free of weeds and other potential food sources for 35 to 40 days before planting,” says Venter. This helps starve larger larvae that are already active in the soil and reduce populations before the crop is established.
Where conventional tillage is used, working the soil during roughly September and October can also help disrupt cutworm pupae and reduce population pressure.
Farmers should inspect fields for cutworm before planting, particularly where weeds, green organic material or crop residues are present.
“Larvae can sometimes be found by digging into the soil to a depth of around 5 to 10cm, although they can be difficult to spot,” says Venter. “Pupae are particularly hard to see because of their brown colour.”
Early detection is important because once seedlings are being damaged, the window for preventative action has narrowed.
“The most obvious sign of cutworm is a young maize plant that has been cut off at soil level,” Venter explains. “Smaller larvae may instead cause small holes in leaves, which can easily be confused with damage from other pests.”
Where chemical control is necessary, timing and placement are important. A ground spray applied to relatively clean soil gives the insecticide a better opportunity to contact larvae. Heavy layers of maize husks, soil clods or other material can shield them from the spray.
“Don’t wait for severe damage,” Venter advises. Once significant stand losses have occurred, control becomes more difficult and replanting may be necessary. Baits applied to moist soil can provide another option in some situations, while additional insecticide applications may help reduce populations, depending on the circumstances.
Farmers should also keep records of where infestations occurred and use this information when planning the following season. Neighbouring fields should be considered too, as adult moths can fly between farms and lay eggs in nearby fields.
Cutworm cannot always be avoided, but early preparation can reduce the risk. Keeping fields weed-free ahead of planting, scouting for larvae, understanding where previous infestations occurred and applying control measures strategically can help farmers protect plant stands and avoid costly losses.
