Field surveys in Dane, Iowa, Monroe, and Richland counties during the second week of June found soybean aphids in 10 of 17 fields. Aphid densities were up to 30 per plant on 1-18 percent of the plants.
According to the report by weekly Wisconsin Pest Bulletin (WPB), very few soybean aphids were found in 20 fields that were checked in other counties.
It observed, however, that the colonizations by the aphids were relatively early this year and advised crop consultants and soybean growers to check closely for infestations within the next two weeks.
Populations of bean leaf beetles were also detected in soybean fields in Rock, Sauk, Jefferson, Richland, and Dane counties. Defoliations were minor - 5-25 percent in most cases - but the WPB suggested that more damage could occur in the coming weeks.
Another significant event during the reporting week of June 6-12 was the catch of 154 corn earworm moths in traps near Janesville.
The WPB noted that because the primary flight of those moths usually does not occur until August and because the development of corn is slow this year it is likely that eggs might be laid and larvae would hatch on pea, pepper, and cabbage plants instead by later this month.
There's a similar lack of synchronization between the flights of European corn borer moths and corn maturity, the WPB observed.
As a result, it warned that first generation larvae infestations could strike snap beans, potatoes, peas, peppers, and weed plants.
The combination of wet weather and slow crop development has also been favorable for slug populations, both in some vegetable crops and in corn fields that are no-till and have lots of surface residue or weeds, the WPB indicated.
However, the wet soils and occasional flooding have been fatal to many corn rootworm larvae or have deterred their ability to attach to corn roots, according to the findings in Green, Dane, Monroe, Walworth, and Rock counties, the WPB pointed out.
Until corn reaches the V-4 growth stage, damage by black cutworm larvae is possible, the WPB noted.
It cited reports of light rates of injury in Columbia, Marquette, Waushara, Green, Waupaca, Green Lake, Sauk, and Rock counties during the first half of June.
Stalk borer infestations are also possible in corn as larvae migrate from grasses and broadleaf plants, the WPB stated.
It recommends treatments if there's feeding on 5-10 percent of the plants by late June.
True armyworm larvae were found in 5-of-60 corn fields inspected during the reporting week.
The WPB mentioned the possibility of infestations in winter wheat and corn fields, suggesting treatment on the latter if there are at least two larvae on 25 percent of the plants or one larva on 75 percent of the plants.
Defoliation by alfalfa weevils was severe in the alfalfa fields that were not harvested by mid-June, the WPB reported.
It noted that populations of other alfalfa pests - potato leafhoppers, meadow spittlebugs, and pea aphids - were quite low.
Colorado potato beetle eggs were laid and about to hatch, the WPB noted. It recommends a Bt insecticide treatment if there's 20-30 percent defoliation on pre-flowering plants at six to eight inch heights.
Among orchard pests, the major concern during the reporting week was catches of codling moths at an economic damage threshold - more than five per trap - at 9-of-27 monitoring sites.
The top total was 81 male moths at Beldenville in Pierce County. A larvicide treatment is suggested once larvae begin to hatch.