No. 1 Article 3/March 16, 2005

IPM and IRM Perceptions and Considerations Regarding Corn Rootworms: Preliminary Results from a Distance Education Workshop

On February 4 and 11, 2005, a two-part, multistate distance education workshop on corn rootworm management was conducted by the following land-grant university instructors: Jon Tollefson (Iowa State University), Ken Ostlie (University of Minnesota), Lance Meinke and Bob Wright (University of Nebraska), Larry Bledsoe (Purdue University), and Mike Gray and Kevin Steffey (University of Illinois). Kevin Steffey and David Feltes (IPM Extension educator, University of Illinois) were the primary organizers for this workshop. Sue Ratcliffe, North Central Region IPM facilitator, also played an important logistical role in making the program a reality.

As part of this long-distance education program, we conducted a preworkshop survey of participants to assess their current corn rootworm management knowledge and their overall perceptions regarding IPM (integrated pest management) and IRM (insect resistance management) with respect to this insect pest. As of late February, we had received a total of 195 completed surveys from six states: Illinois (97), Iowa (21), Minnesota (34), Nebraska (5), South Dakota (17), and Wisconsin (21). Participants of the workshop varied in their occupations, according to the following categories: producer (28.7%), crop consultant (16.4%), Extension employee (5.1%), agribusiness (43.6%), and other (6.2%). Producers varied considerably in the size of their farming operations: <100 acres (8.1%); 101 to 250 acres (14%); 251 to 500 acres (12.7%); 501 to 1,000 acres (24.4%); 1,001 to 1,500 acres (17.4%); and more than 1,500 acres (23.2%).

More surveys will likely be sent to us, so please consider the following results as preliminary. In addition, we will present only a subsample of questions and responses in this article. At a later date, we intend to present the full set of results in a different format. Finally, these results represent the opinions of participants (n = 195, as of February 2005) who took part in our workshop and, thus, do not represent a random sample of survey respondents. Nonetheless, in light of what may be a very challenging growing season (with re-spect to pest management), we thought our readers would find the preliminary responses to many of our survey questions of interest.

Subset of Corn Rootworm Distance Education Workshop Survey Questions

Do you believe that without management of corn rootworms each season, on your farm, significant yield losses would occur due to larval injury?


Do you scout your fields and use economic thresholds before making a decision to use a control product for corn rootworms each season?


Do you leave a check within your field to evaluate the performance of corn rootworm-control products?


Do you consider the prevention of insecticide resistance to be an important issue in designing management programs?


Are you concerned that because of widespread use of seed treatments that resistance may develop in insect populations?


Do you believe that IRM protocols should be developed and implemented for seed treatments?


Do you believe that treating soybean fields with a broadcast insecticide in the eastern Corn Belt to prevent egg laying by variant western corn rootworms is a good management approach?


In the eastern Corn Belt, would you consider applying a tank mix of an insecticide and fungicide to soybeans to suppress egg laying by western corn rootworms and also prevent yield losses if soybean rust develops?


Participants in this workshop reflected real concern that western corn rootworms present a significant management challenge (91.5%) each growing season. Yet only a narrow majority (51.2%) of producers scout fields and use an economic threshold in helping them select the most appropriate corn rootworm management option. A majority of respondents (60.3%) indicated they do not utilize a check to assess the value of a corn rootworm-control product. In our on-farm research studies conducted in the early 1990s (continuous corn production systems), we determined that approximately 50% of fields did not support economic infestations of corn rootworm larvae. As we all know, insecticide products tend to work very well when corn rootworm larvae are not present. Because so many producers fail to leave checks, many operate with an inaccurate assumption that a product has performed well, when in reality, densities of corn rootworms may have been very low in the field.

Respondents indicated concern (64.8%) that insecticide resistance may develop within insect populations be-cause of the widespread use of seed treatments. A significant majority of participants (74.7%) believe that resistance management protocols should be developed and implemented for seed treatments. This response was a bit surprising. However, why should the transgenic technology be singled out as an IPM tactic where the development and implementation of resistance management protocols are required prior to registration of a product?

Although we have spoken extensively about our concerns related to treatment of soybean fields to suppress egg laying by western corn rootworm adults, many respondents (30.2%) indicated they believe this practice is a good management approach. In addition, many (58.3%) of the workshop participants indicated they would consider using a tank mix of an insecticide and a fungicide to treat soybean fields if soybean rust develops this season. The indiscriminate treatment of soybean fields with insecticides may trigger significant problems with soybean aphids in 2005 because of the reduction of natural enemy densities.

As we work through the upcoming growing season, we believe an adherence to the principles of IPM may be more important than in any year we can remember. We look forward to your e-mails and telephone calls throughout the year.--Mike Gray and Kevin Steffey

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