Meet your secondary pests

Published on: 14:28PM Feb 18, 2011

Caydee Savinelli

Do you know what lives in your soil? A bit of scouting before planting to identify pests can save you bushels this fall.
Here are some yield-robbing “secondary pests” that are becoming more common in many fields: 
  • Cutworms in the larval stage are caterpillars that cut plants at or just below the soil line. Often plants will appear wilted or stunted with the whorl of the plant often dead or dying. Most of the plant will not be consumed, merely eaten enough near the soil surface to cause it to fall over.
  • Grape colaspis larvae are very small, grayish-white or tan, stout, curved, and grub-like, with three pairs of legs near its head. When large populations of larvae develop, lateral roots, root hairs, and soft parts of underground stems are consumed. This injury becomes evident above ground as areas of yellow and stunted plants develop; and sometimes purpling of the leaves indicating a phosphorus deficiency, along with browning of the leaf tips and edges. Injury is more severe when weather conditions retard the growth of the seedlings.
  • White grub eggs are pearly white and oval, and are laid from one to several inches deep in the soil. Larvae are white, C-shaped, with 3 pair of prominent thoracic legs, just behind a brown head. Larval root feeding can cause severe damage or death of young corn seedlings. Pruned roots cause rolled and/or discolored (yellow and purple) leaves. Plants are stunted and may die, even after the corn is 1-2 feet tall.
  • Wireworms can attack the crop as soon as seed is planted. The eggs are generally pearly white, round and difficult to see in the soil, and newly hatched wireworms are white with dark jaws. After feeding and molting several times, these larvae become hard, slender, jointed and shiny – generally orange, brown or yellow in color.  Most species tend to prefer heavy, moist soils, especially muck soils.

If you spot one or more of these insects in your field, check to see if you have reached critical populations of one, or some combination of, these pests, and consider using a soil-applied insecticide to protect your yield.

Caydee Savinelli is a technical brand manager for insecticides, responsible for several active ingredients developed and marketed by Syngenta Crop Protection.  She has focused on insect control throughout her career with Syngenta and legacy companies.  Caydee holds a doctorate in entomology from North Carolina StateUniversity.