Corn rootworm beetles started emerging in southeast and south central Nebraska and scouting is recommended. An average of 5-10 beetles per ear usually can seriously affect pollination.
Figure 1. Japanese beetles will first feed on the leaves of soybean (left) and corn. In corn they'll move to the silks (right) when they become available. (Photos by Justin McMechan)
Japanese beetles are emerging in eastern Nebraska and will continue to emerge for the next couple of weeks. As numbers will be highest in field margins, growers are advised to scout across the whole field before determining the need for treatment.
While European corn borer numbers have greatly decreased regionally since the introduction of the first Bt corns, local populations may still cause damage on untraited corn such as popcorn or white corn or in field planted to non-BT corn to take advantage of lower seed costs. These fields should be scouted now.
White-margined Burrower Bug nymphs have been identified in high numbers in a soybean field near Beatrice. This pest is seen periodically in Nebraska in a variety of crops.
Figure 1. The differential grasshopper, one of four grasshopper species in Nebraska that feed on crops. The others are the twostriped, redlegged, and migratory grasshoppers.
Heavy populations of immature grasshoppers were found in field borders in south central Nebraska corn fields this week. Scout and if numbers warrant, treat now when they're small and concentrated in borders. See story for identification tips, treatment thresholds, and control recommendations.
UNL Extension Entomology is monitoring crop insect pests (primarily moths) using black light traps at the Haskell Ag Laboratory near Concord, the South Central Ag Laboratory near Clay Center, and the West Central Research and Extension Center near North Platte.
Figure 1. Alfalfa weevil larvae and adults collected in a single 12-sweep sample in Goshen County, Wyoming by Dan Keener on May 11, 2018. Note that both large larvae and adults are present.
High populations of alfalfa weevils have been found in alfalfa throughout the Nebraska Panhandle; lower populations were reported this week in central and eastern Nebraska. The economics would warrant continued scouting through June to provide for timely treatment, if necessary, and yield protection.
As corn begins to emerge, be alert to the potential for damage from early season insects such as cutworms, wireworms, white grubs or wheat stem maggot. Seed treatments provide some protection, but can be overwhelmed in some circumstances, allowing losses.
