Pest tracking coincides with start of growing season

Ray Mueller
The brown marmorated stink bug is an invasive species of agricultural and urban importance, so it is essential to keep track of its occurrence and expansion in Wisconsin, and to provide an early warning system to help protect crops and prevent home invasions.

MADISON – A few brief periods of warm weather during the early weeks of spring stimulated the migration or emergence of a number of pests that could soon be a threat to crops, according to the first weekly Wisconsin Pest Bulletin (WPB) of the season.

During the second week of April, the WPB noted a significant migration of black cutworm moths, as indicated by the catch of 201 moths in Department of Agriculture, Trade, and Consumer Protection (DATCP) traps in the south central part of the state. This was followed by the catch of another 200 moths during the following week and of 635 moths during the week of April 20 to 26.

The catch of 1,036 black cutworm moths (137 of them in Dodge County) in 45 traps during three weeks in April suggests “an elevated risk of larval infestations in emerging corn in May,” according to the WPF. It added that delays in spring tillage, wet fields, and growth of winter annual weeds would accommodate infestations of black cutworm larvae in newly emerged corn.

In the Janesville area, 29 true armyworm moths were caught during the April 13 to 19 period. Based on that, the WPB advised its cooperators to have blacklight traps in place by May 4.

Pupation of European corn borers (ECB) had begun in southwest localities before the end of April, the WPB reported. It cited a slight increase to 11 larvae per 100 corn plants in that area during 2016 and warned corn growers to expect a somewhat greater pressure from the ECB this year.

Stink Bug Concern

An emerging concern in Wisconsin is the establishment and spread of the brown marmorated stink bug (BMSB), which has been causing major losses in mid-Atlantic and other states in recent years, the WPB pointed out. In addition to fruit crops, soybeans and corn could be vulnerable to the pest, it noted.

During this spring, the University of Wisconsin insect diagnostic laboratory has confirmed 34 reports of the BMSB in the state, the WPB stated. Most of the specimens have come from the Madison area in Dane County but others have been found in Jefferson and Walworth counties and few other locations. Minnesota's first identification of the BMSB occurred in August of 2016 in Dakota County, which borders Wisconsin.

Gypsy moth egg hatches were detected by April 21 in Dane County. The WPB suggested treatment of egg masses with horticultural oils in the central and northern areas before hatching begins.

Alfalfa Insect List 

By April 24, alfalfa weevil adults and egg deposition were verified in field surveys in Columbia, La Crosse, and Monroe counties. The favorable weather in February set the stage for the possible emergence of alfalfa weevil larvae by May 2 in Rock and Grant counties, the WPB observed.

Although tarnished bugs were plentiful during the early alfalfa field surveys, they are not a threat to that crop but rather to strawberries, apples, and flower buds in the coming weeks, the WPB explained. The hatching of pea aphids began by April 17 but populations were low, the WPB noted.

Common asparagus beetle activity was documented near Beloit, Platteville, and La Crosse in late April. The WPB suggested control if beetles were found on five to 10 of 100 spears or if eggs were laid on at least two of 100 spears. Cabbage maggots flies and imported cabbage worm adults were also active.

Fruit Crop Pests

Larvae of the eastern tent caterpillar have been active since late March, the WPB reported. When found on apple, ornamental apple, wild cherry, or other host tests, the tents full of larvae should be removed manually within the next week or two, it advised.

Among other apple orchard pests, the WPB noted that spotted tentiform leafminer flights began in early April, red banded leafrollers were being caught in traps, and oblique banded leafrollers were active under the bark of orchard trees. For the latter, it advised scouting with a 10x hand lens once leaves open and flowering begins.