Volume 64 Number 9 Date 06/27/2019
JAPANESE BEETLE - Adults are likely to begin appearing in the week ahead. Damage to fruit trees, ornamentals, nursery stock and field crops can be expected for the next two months across most of the state, with peak beetle emergence occurring by early August. Soil-applied systemic insecticide treatments must be made 3-4 weeks in advance of beetle emergence and are no longer advised.
EUROPEAN CORN BORER - The tallest corn is now susceptible to infestation by first-generation corn borers. Leaf feeding and small larvae were observed on June 26 in Dane County. Early signs of damage, including leaf pinholes and shot holes, should be noticeable in southern and central Wisconsin fields next week.
SPOTTED WING DROSOPHILA - Emergence of flies was documented in La Crosse County on June 17. The first capture of SWD adults in survey traps should be viewed as an early warning to fruit growers to increase monitoring efforts and make preparations for SWD management.
SOYBEAN APHID - Early colonies were observed for the first time this season on June 19 in Columbia County. Surveys this week detected aphids in three of 24 soybean fields sampled. Densities were low and ranged from 1-6 per infested plant on 1-4% of plants. The aphids were found in Eau Claire, Pepin and Trempealeau counties.
POTATO LEAFHOPPER - Nymphs are appearing in alfalfa. Counts of this stage and the adults are currently below the economic threshold of one per sweep in 8- to 11-inch fields and two per sweep for alfalfa 12 inches or taller, but populations could increase abruptly with the hot weather ahead. Routine sampling of second-crop alfalfa is recommended.
TRUE ARMWORM - Larvae are migrating into the perimeter rows of corn, and reports indicate localized problems have developed in a few Fond du Lac County fields. Increased monitoring for first-generation armyworm larvae is particularly important at this time.
CORN ROOTWORM - Peak or 50% egg hatch should occur by July 1 near Madison. The first beetles usually appear around Independence Day, but will be 1-2 weeks late this year.
LILY LEAF BEETLE - UW Entomologist PJ Liesch has confirmed the distribution of this pest in Taylor County, noting that the recognizable bright red beetle may have been established in the area for a year or two. Taylor is the eighth Wisconsin county in which the lily leaf beetle has been detected since 2014, in addition to Langlade, Lincoln, Marathon, Oneida, Portage, Shawano, and Wood.
APPLE MAGGOT - Apple growers concerned about this pest are advised to set a minimum of three traps per 10 acres before the end of the month, increasing the density in July to one trap every 200-300 feet along the orchard perimeter. The traps should be hung at eye-level adjacent to wild hosts and near early-ripening cultivars. Last season, the first flies were captured during the week of June 21-27.
-- Krista Hamilton, DATCP Entomologist