Pest concerns vary in state's crops

Ray Mueller
A maggot of a spotted wing drosophilia is seen in this raspberry.

MADISON – Although raspberries had not yet begun to turn color, the presence of spotted wing drosophila egg-laying flies was reported in Dane, Door, and La Crosse counties in June, according to the latest weekly issue of the Wisconsin Pest Bulletin (WPB) compiled by the Department of Agriculture, Trade, and Consumer Protection.

The concern with the spotted wing drosophila is that the eggs hatch and appear as white larvae just as the raspberries are ripe for picking. Various detection and control practices described by Extension Service specialists in several states are available online by searching for information on spotted wing drosophila.

The weekly WPB also called attention to the emergence of apple maggot flies by the third week of June and to the accumulation of enough growing degree days to prompt the appearance of the first generation of codling moths in apple orchards.

Corn pest list

Growers of conventional field corn hybrids and sweet corn were advised to check for the presence of European corn borer larvae in the whorls of corn plants. Concerns about stalk borers was confined to several western counties where 1 to 11 percent of corn plants in field edge rows were damaged, the WPB reported.

Some populations of true armyworms were found in corn, particularly in weedy fields. Growers were also advised to check for black cutworms until corn reaches its V5 growth stage.

Pheromone traps are being set for a 10-week tracking of the flight of western bean cutworm moths. The hatching of corn rootworm beetles was set to begin by the last week of June, the WPB noted.

Soybean pests

With the many cases of excess field moisture, the presence of slugs has emerged as a concern in soybeans. However, the WPB pointed out that no economic threshold has been set for potential losses due to slug feeding.

The early season populations of soybean aphids are quite low but that could change once soybeans reach their reproductive stage, the WPB observed. A bit of soybean plant defoliation by the rose chafer was reported in western counties.

In alfalfa fields, the populations of pea aphids, alfalfa weevils, and meadow spittlebugs are on a typical seasonal decline, the WPB indicated. The only remaining concern is with a possible buildup of potato leaf hoppers.

Vegetable crops

The WPB also pointed out that potato leaf hoppers are a potential threat to snap beans and potatoes as the second cutting of alfalfa is taken.

Other concerns for vegetable growers are the upcoming hatch of squash vine borer eggs on pumpkins, squash, gourds, and other vine plants, the egg-laying by imported cabbageworm butterflies, and the development of conditions sufficient for causing late blight on tomatoes and potatoes.

Full WPB reports, which are coordinated by DATCP entomologist Krista Hamilton, are available online at Weekly updates are posted on Thursday afternoons