Personnel from Ohio State University Extension sampled for first-year, western corn rootworm adults (FYWCR) in soybean fields for the eighth year. The final data from the 2004 rootworm trapping program have been assembled. This is an overview of the results from that survey. Sampling was done using Pherocon? AM yellow sticky traps placed in 78 fields in 19 counties ( see map). Six traps were placed in the soybean on metal posts at canopy height and located at least 100 feet from the field edge and evenly spaced in the field. The traps were initially placed in fields as early as July 20 and removed as late as mid September. Traps were serviced once a week throughout the 6 to 7 week survey. A new, clean trap was installed to replace the insect and debris covered, week old trap at the end of each week of trapping. After each trapping week, the number of beetles collected were summed and divided by the number of traps (6) and the number of days the traps were in the field resulting in the average number of beetles collected per trap per day.
A summary of the weekly catches of WCR adults per trap per day from the 2004 growing season is presented in Table 1. Research indicates that catches in soybean of 5 or more beetles/trap/day during any trapping week indicates a potential problem with rootworm in the field the following year.
The trapping data from 2004 had the following results:
Three fields had an average > 5 beetles/trap/day
Seven fields had an average between 4 and < 5 beetles/trap/day
Six fields had an average between 3 and < 4 beetles/trap/day
Eight fields had an average between 2 and < 3 beetles/trap/day
Twenty fields had an average between 1 and < 2 beetle/trap/day
Thirty-four fields had an average < 1 beetle/trap/day.
Last year, none of the fields surveyed ever had > 4 beetles/trap/day. In addition to sampling with the sticky traps, this was our second year to sweep soybean fields in 9 counties along the Ohio-Indiana border for FYWCR adults during the 2nd week of August. Twenty sweeps in 5 places in 2-3 fields per county were taken. The contents of the nets were bagged and then counted in the lab. Sweep net samples do not tell us if a field has a high enough FYWCR adult population to warrant treatment the next year, but they do tell us the relative abundance of the beetle population. The number of WCRA per 100 sweeps ranged from 0 to 51 (see map). Although populations were not as high as fields in states to our west, they were higher in 2004 than last year in Ohio.
Based on the potential treatment level of 5 beetles/trap/day during any trapping week, if any of the three fields with over 5 beetles/trap/day are planted to corn in 2005, a treatment of either a soil insecticide, Poncho 1250 or Cruiser CRW seed treatments (the highest rate of each), or a YieldGard Rootworm transgenic corn should be considered for control of rootworm. These data from both sampling procedures do not mean that other fields in a county that were not sampled do or do not need treatment but it does give good information about the fields that were sampled and about the abundance of the beetles this year. Overall, rootworm populations continue to be relatively low. However, some soybean fields did have populations sufficient to warrant treatment next spring, and suggest that perhaps first year western corn rootworm is increasing in population size and distribution in Ohio. Because of this possibility, the need to continue sampling for western corn rootworm adults in soybeans in 2005 is great.
Counties and personnel involved with the first year corn rootworm trapping in 2004.
| County | Agent | County | Agent |
| Allen | C. Young | Morrow | S. Ruhl |
| Auglaize | J. Smith | Paulding | J. Lopshire |
| Crawford | S. Prochaska | Putnam | G. Arnold |
| Darke | S. Foster | Sandusky | M. Koenig |
| Defiance | B. Clevenger | Seneca | E. Lentz |
| Fulton | G. Lebarge | Shelby | R. Bender |
| Henry | D. Sonnenberg | Van Wert | A. Kleinschmidt |
| Hancock | G. Wilson | Williams | F. Chirra |
| Mercer | T. Mangen | Wood | A. Sundermeier |
| Miami | H. Watters | ||
Funds for traps were provided by Pioneer Hi-Bred International and the OSU Extension Agronomic Crops Team.
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