|
|
Above-normal temperatures accelerated summer crop maturation across Wisconsin during the last week of August, although the searing afternoon heat caused some disruptions to harvesting and other fieldwork. Weekly average temperatures broadly ranged from 1 to 5°F above normal, with highest daytime temperatures reaching the middle 90s (degrees F). The most intense heat of the season occurred August 26 and 27 and was followed by beneficial rain that moderated the effects of the stressful temperatures on crops. Weekly rainfall was highly variable across the state. Mainly dry conditions in far southeastern Wisconsin contrasted with locally heavy rain (up to 3.0 inches) in the northwest.
According to the USDA NASS, 90% of the state’s soybeans were setting pods as of August 25, four days ahead of last year and the five-year average of 86%. Meanwhile, corn in the dough (R4) stage reached 73%, equal to last year and two days ahead of the five-year average. The fourth crop of alfalfa was 20% harvested, compared with 21% on average.
DATCP’s field staff continued late-season survey work despite the heat. Activities for the week ending August 29 included sampling corn for rootworm beetles, checking various insect survey traps, completing seed field inspections for export certification, and removing spongy moth traps.
__________________________________
|
|
DATCP’s annual corn rootworm beetle survey was finalized this week. The survey assesses current-year beetle populations and can be used to forecast larval root damage potential in next season’s corn crop. Corn rootworm is considered the most damaging and expensive pest to corn production in the U.S., causing well over $1 billion in yield losses and control costs each year.
Results of sampling throughout August indicate beetle pressure in corn fields has been moderate this season and similar to levels recorded in 2023. The survey found a state average count of 0.5 beetle per plant, the same average documented last season.
As shown in the map and table below, average beetle counts decreased in five of the state’s nine crop reporting districts and increased in four districts. The highest averages were recorded in the southwest (0.8 beetle per plant), east-central (0.7 beetle per plant) and northwest (0.6 beetle per plant) regions, though only the southwest district had an average beetle count exceeding the 0.75 beetle per plant economic threshold. Corn fields with high or above-threshold beetle populations comprised 15% of this year’s 229 sites, a decrease from last year’s 18%. |
|
In addition, the 2024 total count of 1,151 rootworm beetles on 2,290 corn plants sampled statewide was very comparable to the 1,174 beetles tallied in 2023. While the overall corn rootworm count was not surprising, the season’s most unexpected outcome was the shift in beetle composition in favor of the western species. Fifty-two percent (600 out of 1,151) of this season's beetles were the western corn rootworm, 45% were the northern species (523 out of 1,151), and 3% were the southern species (28 out of 1,151). The western corn rootworm has not been the predominant species in the state since 2013.
Although the survey documented the continuation of mostly low and moderate beetle populations in Wisconsin corn fields this season, areas of high rootworm pressure were found in the southern, east-central, and northwestern districts (see orange circles in the survey map below). Effective corn rootworm management in these higher-pressure regions will continue to require a multiyear plan emphasizing crop rotation (out of a continuous corn cropping system), selection of a dual or stacked mode of action Bt-rootworm (RW) and RNAi corn seed product and, in some situations, the use of a soil-applied insecticide at planting—usually for corn products without Bt-RW protection. Crop rotation remains the most effective regulator of corn rootworm populations by breaking the lifecycle and should be the foundation of integrated rootworm management. |
|
__________________________________ |
|
Another season of orchard insect reporting has ended, with significant apple maggot and codling moth activity still occurring at some cooperating sites. Although it is not necessary to send in insect counts after August 29, apple growers can expect lingering pest pressure throughout harvest and are advised to maintain traps until late September.
Despite surplus rain earlier this season, apple maggot pressure has not been particularly high, as is usually the case during wet summers. Trap counts peaked July 19-August 1 and have been variable this month, with a few orchards reporting large weekly captures of 15 flies per red sphere trap, while other sites have not trapped a single apple maggot fly. The external depressions and brown, internal larval tunnels resulting from this pest are now appearing on infested fruits. Continued monitoring of traps for at least two more weeks is suggested since the flies are still active and could cause problems in late-ripening apple varieties.
As for codling moth activity in orchards, the second-generation flight has declined markedly, but a few orchard locations continued to register above-threshold counts (five or more flies per trap per week) in the past week. The cooperators in Columbia, Fond du Lac, and Oneida counties reported captures of five, six, and eight moths per trap, respectively. The codling moths now flying will produce more larvae into September, which could pose a threat to Honeycrisp and other late season varieties. Orchards that have recorded large summer-generation moth flights should continue trap checks since counts in September can be an indicator of spring moth pressure and damage potential by the first generation of larvae next June.
The Pest Survey Program wishes to thank our dedicated network of apple growers and all of our cooperators for their reliable weekly reporting again this season. Data supplied through their efforts is vital to integrated pest management programs and contributes to reduced damage and pesticide use. End-of-season summaries of the 2024 insect counts will be posted on DATCP’s various pest monitoring pages next month. |
|
 __________________________________
|
|
Large late-season migration flights of corn earworm moths were registered for the second week in a row. DATCP’s pheromone trapping network captured 3,357 moths August 23-29, for a cumulative total of 4,668 moths in 15 traps. The monitoring site near Beaver Dam in Dodge County reported a particularly high weekly count of 884 moths.
The recent surge in corn earworm moth activity in the last two weeks signals that the threat to fresh market and processing sweet corn has increased and egg laying is intensifying in fields where green silks are available. Sweet corn growers are encouraged to continue monitoring fields and following DATCP’s corn earworm migration reports through mid-September. Treatment schedules based on nightly corn earworm moth trap catches are available at: Commercial Vegetable Production in Wisconsin (A3422 pg. 278). |
|
 __________________________________
|
|
Western bean cutworm moth flights have ended at all pheromone trap monitoring locations. The 2024 state total count is 15,681 moths in 69 traps (227 per trap average), an increase from last year’s previous record-setting catch of 9,309 moths in 42 traps (222 per trap average) and the new all-time highest state average count since western bean cutworm trapping surveys began in 2005. The highest individual trap count for the season was 1,834 moths near Crivitz in Marinette County, while one-third of the sites recorded cumulative counts above 250 moths per trap for the season.
This summer's large moth emergence has produced scattered heavy larval populations in the central, northern, and western areas of the state. Surveys in field corn this month found western bean cutworm caterpillars in ear tips at 10% of the sites sampled—indicating infestations are common. Most larvae resulting from this summer’s flight should cease feeding and transition to the pre-pupal overwintering stage by early September.
For final regional western bean flight data extending across the northeastern U.S. and adjacent Canadian provinces, please see the Great Lakes and Maritimes Pest Monitoring Network (select WBC tab). |
|
|
__________________________________
|
|
|
|
|
