Scout Early for Below-Ground Insects that Damage Corn
During emergence and early growth stages, below-ground insects can damage your corn stand. As you scout fields and pests this growing season, share field notes with your Latham dealer. Those notes are key to building a crop plan that offers the best protection for 2023 and beyond.
Let’s focus on four pests, including where you will likely find them and management tips to prevent damage: White Grubs, Seedcorn Maggots, Black Cutworms and Corn Rootworms.
- White Grubs. Scout for grubs prior to planting. Larvae, or grubs, are white with brown heads and three pairs of legs. The end of the abdomen is smooth and shiny with dark body contents showing through the skin. Grubs may be more than one inch long when mature and curl into a C-shape. They have two parallel rows of small, stiff hairs on the underside of the abdomen. High-risk fields include those that have been in pasture for one or two years previously or where willow or cottonwood trees grow adjacent to the field. If you see grubs after planting, note this so you remember it when planting this field to corn next. Most of Latham Seeds’ seed treatments will control grubs unless infestations are high enough to overwhelm the seed treatment. In those instances, consider soil-applied insecticide.
- Seedcorn Maggots: When soils are cold and germination conditions are less than ideal, maggots can destroy seed. The best time to scout is from planting to VE. Dig up seed in areas with a poor stand and look for seed feeding. Fields with the highest risk are those where manure was applied in winter and spring; where green vegetation is incorporated in spring; and those with cool, wet soil. Potential for injury is minimal in no-till fields or where old crop residue is buried. Most infestations will be controlled by the seed treatment. Note problem areas, so they may be addressed the next time corn is planted there. In addition to using seed treatments, consider soil-applied insecticides in those areas.
- Black Cutworm. Damage is most common in low or poorly drained areas of fields. Young cutworms feed near the surface, but they soon burrow into the ground and cut plants below the soil surface. Plants cut above the growing point often recuperate, but plants cut below the growing point will die. Black cutworm larvae are up to 1.75 inches long. They’re light gray to black with granular-appearing skin. They have four pairs of fleshy prolegs on the abdomen. Black cutworms are best identified by the dark tubercles found along the middle of the back. On each body segment, the pair of tubercles closest to the head is about one third to one half the size of the pair nearest to the abdomen. Latham brand hybrids with SmartStax® and Duracade will control most cutworm infestations. Our new TreceptaTM-traited hybrid for 2022 planting contains the Vip3A Bt protein that also offers great control.
- Corn Rootworm. We generally see evidence of two species of corn rootworm in Latham territory. Northern corn rootworm beetles are tan or light to dark green without markings on their wings. Adults are about ¼-inch long. Western corn rootworm beetles are yellow to light green and have three dark stripes on the forewings. It looks like they have a single black stripe on the wings; the stripe does not extend to the tip of the forewings. Adults are about ¼-inch long and can be confused with other rootworm adults or striped cucumber beetles.Striped cucumber beetles have very distinct stripes along the wings that extend to the tip of the abdomen. Their underside is completely black. Corn rootworm larvae are slender and white with a dark brown head and a dark plate on the top side of the tail section. The maximum size is about one-half inch. Larvae have three pairs of legs on the thorax. Young larvae, shortly after egg hatch in May and June, begin feeding on root hairs and tunnel inside roots. As they develop, larvae begin feeding on larger root tips. Extensive feeding can eliminate entire nodes of roots. In fields with a history of corn rootworm, plant a Latham brand hybrid with SmartStax or Duracade technology. In fields with heavy pressure, a soil-applied insecticide in addition to a traited hybrid will help control this pest.
We are excited to have a new option to control rootworm going into the 2023 season! You can see Latham’s NEW SmartStax Pro hybrids in plots this summer. Contact your Latham Dealer to see how this technology can protect roots from feeding. If your local dealer doesn’t have a plot containing a SmartStax PRO hybrid, his Regional Sales Manager (RSM) can help him find one for you to visit. We look forward to seeing you soon… in a field near you!