Although the growing season or harvest has been completed for some crops and is winding down for others, the time has not yet arrived to let down the guard on pest threats, according to the Wisconsin Pest Bulletin (WPB) report for the third full week of August.
Based on heavy catches of moths, especially in Fond du Lac and Dane counties, sweet corn growers were again advised to be on the alert for corn earworm infestations in fields that are still silking.
Moth catch totals during the reporting week included 272 at Byron in southern Fond du Lac County and 227 at the north Sun Prairie site and 162 at McFarland in Dane County.
Corn rootworm beetles counts have been completed for the year in five of the state's nine agricultural statistical districts.
Of the 156 fields in the survey, 28 had infestations above the .75 per plant average that is the threshold for predicting economic loss from root damage in a corn crop the following year.
Some of those fields registered counts of three-eight beetles per plant. They are in Columbia, Dunn, Grant, Green Lake, Lafayette, Rock, and Walworth counties.
An average of .2 beetles per plant was detected in the surveyed fields in the central district while the west central district had an average of .4 beetles. The average for the five districts .5 per plant, including the high of .8 in the southeast district.
Western bean cutworm trapping was completed in the state by the end of the third week of August. This year's catch of 642 moths in 116 pheromone traps was only 20 percent of the total caught in 2012.
The WPB updated apple growers on a variety of pests. Stink bugs, whose adults and nymphs were found on the underside of leaves in southern Wisconsin orchards, were mentioned for the first time this year in the weekly reports.
Catches of codling moths in pheromone traps continued to be relatively high, including 32 at Spring Valley in Pierce County, as the reporting sites caught an average of 10 during the week.
Spotted tentiform leafminer moth catches hit a high of 993 as the central and north regions reached the period of major activity.
Apple maggot populations appeared to be leveling, the WPB indicated. It attributed this to a combination of a period of dry weather and insecticide applications.
Reports from home gardeners in Eau Claire and Grant counties indicated damage by Japanese beetles to such crops as snap beans, corn, eggplant, and peppers.
Cabbage looper moth catches were made near Chippewa Falls, prompting the WPB to urge growers of cabbage, broccoli, and cauliflower to scout for larvae until at least mid-September and apply a treatment if the infestation tops 10 percent of the plants.
With tomatoes beginning to ripen, reports of blossom end rot were received. The WPB attributed this perennial problem to a deficiency in soil calcium and to the inconsistent availability of moisture.
One new insect was mentioned for the first time this season in the latest WPB update.
Reports were received from homeowners in southern and western Wisconsin about strawberry root weevils (a black beetle) entering their homes in large numbers. The WPB noted that these insects do not damage structures and do not breed indoors.
With the normal end of the reproductive period approaching, soybean aphid populations had increased somewhat.
Five percent of the fields surveyed during the week had population averages of 250-587 per plant while another 16 percent had counts of 50-249.
As of Aug. 21, the soybean aphid average was running at 49 per plant. The WPB advised an insecticide treatment if populations exceed an average of 250 on at least 80 percent of the plants before they have reached the R5.5 growth stage.
Net sweeps in alfalfa fields, especially in western counties, continued to catch potato leafhoppers, pea aphids, and plant bugs but in all cases the numbers continued to be well below those that would create concerns about crop losses.