Scout for Diamondback Moth in Canola (08/05/21)
Diamondback moth adults and larvae have been observed at economic population levels in northeastern ND canola. The severity of diamondback moth infestations depends on the overwintering population in the southern states and how many moths migrate into North Dakota. The level of feeding injury varies greatly and depends on larval densities and plant growth stage. Larvae feed on the leaves, buds, flowers, seed pods, the green outer layer of the stems and, occasionally, on the developing seeds.
The adult diamondback moth is a small, gray or brown moth about ½ inch long. When the wings are folded, three cream diamond-shaped markings are present, hence the name diamondback moth. Mature larvae are green and about ½ inch long and spin a strand of silk when disturbed.
Diamondback moth larvae can be monitored in the field by pulling all plants from a 1-square-foot area and then beating the collected plants onto a clean surface or into a white bucket and subsequently counting the number of larvae dislodged from plants. Larvae often will dangle from canola plants on a silk thread. Repeat this procedure in at least five locations in the field to obtain an average number of larvae per square foot. The best pest management practices for profitable yields while preventing losses from diamondback moth on canola include early monitoring of adults and larvae, and insecticide treatment only if necessary.