Pest concerns switch to multiple crops in state
Although a virtual "all clear" was issued by the latest weekly Wisconsin Pest Bulletin (WPB) regarding insects in alfalfa, concerns were listed for a variety of other crops entering new growth or reproductive stages.
Vined plants, vegetables, and flowers are targets of a number of pests as egg laying has begun and larvae begin to emerge, the WPB noted.
That is the case with the squash vine borer, which is an annual threat to pumpkins, gourds, squash, and other vined plants
Once adult moth egg layers are noticed, several insecticide treatments on the stems of plants are likely to be needed over a three-week period, the WPB advised.
Earwig populations are relatively high this year as reports of damage to vegetables and flowers have been received from La Crosse, Dane, and Sauk counties, the WPB indicated. Striped cucumber beetles also have begun to appear on vined plants.
The WPB predicted that the first Japanese beetles of the season are likely to emerge within the next 10 days. They feed on fruits, perennials, nursery stock, and field crops for several weeks.
Discoveries of rose chafer beetles on garden plants in Waupaca and La Crosse counties and in soybeans in Juneau and Monroe counties prompted the WPB to also include a caution for vineyards, especially on sandy soils.
It considers two beetles per vine to be the economic threshold for losses and suggested spray treatments, not trapping, in those cases because the commercial traps attract more of the beetles to the area.
Soybean aphid populations were found to be widespread but quite low during the reporting period. Two exceptions were per plant populations of up to 142 aphids in a field near Brooklyn in Green County and of 168 at Dodgeville in Iowa County.
The WPB pointed out that an economic threshold for yield losses is likely with an average per plant population of at least 250 aphids on 80 percent of the plants.
With the continuation of well above normal rainfall through the end of June, defoliation by slugs has been common, the WPB observed.
Damage from the pest was detected on 25-70 percent of the corn plants in some fields in Fond du Lac, Dodge, Columbia, Richland, and Sauk counties.
Corn earworm moths - a total of 33 - were caught during the reporting week in pheromone traps at Janesville, Ripon, and Green Lake.
Low numbers of larvae traced to egg laying by earlier arriving moths were found in 4 of 45 corn fields surveyed during the week.Those were in the V3-V7 stage corn in Dodge, Green, and Iowa counties.
The year's spring flight of European corn borer moths is complete, the WPB indicated. It noted that fresh whorl feeding injury is evident from early instar larvae on non-Bt and Bt refuge corn.
No Western bean cutworm moths were caught at the 95 pheromone trap sites from which reports were received by June 26.
The WPB noted the possibility of catches of the somewhat smaller granulate cutworm moth in those blacklight traps before this year's flight of the WBC moths begins.
In alfalfa fields, the overall populations of potato leafhoppers, plant bugs, and alfalfa weevils were quite low in late June and the year's accumulation of spittle masses created by the meadow spittlebugs was over, the WPB reported.
It added, however, that some yellow striped armyworm larvae were found in alfalfa in Dane and Green counties, leading to concerns that they could move onto corn and cause damage in combination with variegated cutworms and earworms.
True armyworms continued to pose a threat to lodged winter wheat and in corn and pea fields with grassy weeds and were likely to do so until about mid-July, the WPB stated. Field surveys in nine counties in the western half of Wisconsin found minor damage from true armyworms.
Stalk borer damage was detected on up to 8 percent of corn plants in some spots in Green County but at less than 3 percent in Richland, Rock, and Sauk counties.
Apple orchard owners were reminded that the season's second flight of the spotted tentiform leafminer was well underway, leading to the catch of 891 moths in a pheromone trap near Montello and of at least 300 in traps near Rio, Oneida, and New Berlin.
The WPB advised a spray treatment if the miner infestations exceed one per leaf.
Codling moth activity was reported at 12 of 31 monitoring sites, representing an increase from updates in previous weeks. The WPB called for reapplication of larvicide treatments following any heavy rain.
Using sticky traps was urged to identify the presence of apple maggot flies. If necessary, spraying should follow and continue as long as flies are being caught on the traps, the WPB stated.