Vegetable pests a leading concern

Ray Mueller
Now Media Group


For the most part, pest pressure in Wisconsin's major crops was not much of a concern during the first week of July, according to the latest weekly Wisconsin Pest Bulletin published by the Wisconsin Department of Agriculture, Trade and Consumer Protection.

But that's not the case with the pests which feed on a variety of vegetable plants, the WPB indicated. Those which tend to be affected the most are vined plants such as squash, pumpkins and gourds.

The WPB reported that squash bugs were abundant as June turned into July. It also noted that growers of vined plants should be vigilant for at least another week on infestations by squash vine borers.

Battling the beetles

Large numbers of Japanese beetles were feeding on raspberries, apples and grapes in southern and west central counties, the WPB stated. It pointed out that even small blemishes or surface injuries on those fruits can attract large numbers of beetles. Grapeberry moths were indicating the start of the season's second generation of that pest.

Apple maggot flies were detected at orchards in Fond du Lac and Sheboygan counties. While the year's second flight of spotted tentiform leafminer moths was expected to peak soon, codling moth infestations were dropping as the season's 1st flight was completed, the WPB observed.

Colorado potato beetle pressure was likely at its peak for the season. Cabbage caterpillar populations were reported to be high in western and southern counties. Tomato growers were advised to watch egg laying by hornworm moths.

The season's first official detection of spotted wing drosophila flies occurred in Trempealeau County on June 22. Other specimens of the pest were collected in Dane and Door counties.

SWD flies lay their eggs in raspberries and other fruits with a timing that leads to hatching of the larvae at the proper harvest time of the fruit. Owners of crops that could be infested are being advised to confirm the presence of the flies and then apply an insecticide or check for online protocols on how to cope with the SWD.

Insects on corn

Trapping of western bean cutworm moths has begun, resulting in the catch of 28 moths in the 62 monitoring traps. Those catches occurred in Columbia, Dodge, Green Lake, La Crosse, Marathon, Marquette, Monroe, Portage and Rock counties by July 7.

The WPB indicates an action level for treatment when infestation reaches 8 percent of the plants in field corn and 4 percent in sweet corn. It notes that 20 to 200 eggs can be in a single WBC mass.

Inspections for the European corn borer have found that the larvae infestation in most of the 11 percent of the fields which have a population is in less than 10 percent of the corn stalks. A few fields had infestation rates of 15 to 30 percent in the whorls. For stalk borers, the WPB suggested monitoring any corn which has not yet reached the V7 growth stage.

Corn rootworm beetles have begun to emerge in Richland, Sauk and La Crosse counties, the WPB reported. With the peak emergence likely to occur in the first half of August, it advised corn growers in the southwest, south central and east central districts where populations reached 0.8 or more beetles per plant in 2015 to be extra vigilant in the coming weeks.

Insects in soybeans

Surveys of 44 soybean fields during the first week of July found that that 22 of them did not have any presence of soybean aphids. Of those that had a population, the counts continued to be well below what is considered to be the economic threshold for yield losses, the WPB stated.

Some soybean plant defoliation has been observed but in all cases it was below the 20 percent at which an insecticide application should be considered. Among the pests cited for the existing defoliation were Japanese beetles, bean leaf beetles, rose and sand chafers, slugs and caterpillars.