The continuing high migration volume of black cutworm moths is generating concerns among entomologists and agronomists about the potential for significant damage to young corn plants in at least southern Wisconsin within the next 10 days into early June.
According to the weekly Wisconsin Pest Bulletin, another 494 moths, including 54 near Middleton in Dane County, were caught in 43 pheromone traps from April 28 through May 4 at locations in the state's southern tiers of counties. This put the year's total at 1,170 moth catches, triggering a prediction that cutting of young corn stalks by cutworm larvae could begin by May 20 in fields near Platteville, Lancaster and Janesville.
Concerns are minimal this year about any large infestations by the European corn borer, whose relatively few moths emerging from pupae are expected to be in flight within the next week. But a continuation of cold and wet soils in east central and northeastern parts of the state could result in damage to seeds of the earliest planted crops from the seed corn maggot, the WPB warned.
New stink bug territory
Monitoring of the brown marmorated stink bug, which has the potential of causing major damage to many agricultural crops, has been stepped up in Wisconsin following the discovery of reproducing populations in Dane County.
The latest summary reported the discovery of the stink bugs at 16 locations in Dane County, 2 in Jefferson County, and 1 each in Iowa, Dodge, Waukesha, and Winnebago counties. Most of those have been in buildings and urban settings rather than in agricultural locations, the WPB noted.
In the longer term, the concern about the brown marmorated stink bug is what has happened elsewhere, the WPB reported. As it has spread to 42 states and two provinces in Canada, it has become 'a nuisance' in 19 states and a creator of severe problems with one or more agricultural crops in six states.
Alfalfa pests limited
Except for the imminent appearance of alfalfa weevil larvae in southern and western counties, pest pressure is quite low so far in alfalfa stands. In field surveys, WPB cooperators were catching only 1 to 3 adult weevils per 100 sweeps and no larvae were detected by the early days of May.
Pea aphid counts in alfalfa were running from seven to 80 per 100 sweeps. The WPB indicated that the average of 33 per 100 sweeps was more than double the number for the previous reporting week.
Net sweep catches of the tarnished plant bug continue to be low in alfalfa fields with 12 per 100 sweeps being the highest number. The WPB is concerned about the potential for the bug to infest strawberry plants and apple trees in the coming weeks.
The first bean leaf beetles of the season were found in Richland County on May 3. The WPB observed that they can present a threat to the earliest emerging soybeans.
Activities by cabbage maggot flies, the imported cabbage worm butterfly, and flea beetles that can lead to infestations of vegetables were noted by the WPB. It added that potato growers can expect egg-laying Colorado potato beetles to be active by the end of May.
Common asparagus beetles were depositing eggs on asparagus spears in areas where 150 growing degree days (on a base of 50 degrees) had been accumulated, the WPB stated. It suggests an insecticide treatment if at least 5 percent of the plants are infested.
Codling moth emergence was expected to begin in apple orchards as far north as central Wisconsin this week. Before that began, reports from Ozaukee and Richland counties cited the catches of maple tip borers in pheromone traps set out to catch codling moths.
In what is apparently an isolated incident, lily leaf beetles were found to have survived the winter in lily foliage at a residence at Weston in Marathon County. This was the first documented appearance in Wisconsin since June in 2014 of the pest which is destructive to cultivated lilies. The WPB asks gardeners and homeowners in that area to watch for that beetle this summer and to report any sightings to email@example.com.
The weekly WPB update is usually released at about 3 pm on Thursdays. Interested persons can find the full report, which often includes photos of the pests that are being tracked, at datcpservices.wisconsin.gov/pb/pests. A request can also be filed to be put on the email list for the weekly report.