Preliminary Root Ratings Posted for Corn Rootworm Products in Urbana, Illinois Trial

Each year, the performance of corn rootworm products (Bt hybrids and planting-time soil insecticides) are evaluated in several trials at University of Illinois Education and Research Centers located near DeKalb, Monmouth, Perry, and Urbana. The experiments are conducted in plots that were planted to a trap crop (late-planted corn, interplanted with pumpkins) the previous year. A trap crop system is used to help ensure greater levels of rootworm pressure from year to year. In 2013, the level of root pruning in three of the locations, DeKalb, Monmouth, and Perry, was insufficient to adequately evaluate the efficacy of the products. Consequently, only the root ratings for Urbana are provided in this Bulletin article. Later in the year, for those interested, root ratings for all the trials will be published in the on-line onTarget Report that has been referenced in previous Bulletin articles.

Root injury in the untreated checks for the Urbana location ranged from 0.91 (nearly 1 node of roots destroyed) to 1.8 (nearly 2 nodes of roots destroyed). The DeKalb (DKC62-98) check had significantly less root pruning than the other two checks; however, the seed had been treated with a greater rate of an insecticidal seed treatment (Poncho 500). This difference in insecticidal seed treatment rates may have been responsible for these root injury differences among the untreated checks. In general, the insecticides and Bt hybrids provided high levels of protection against rootworm larval injury in the Urbana study. The application of Aztec 2.1G or Force CS to a Bt hybrid did not significantly improve root protection over that of the soil insecticides alone. Root injury was significantly less when Capture LFR was used in combination with certain Bt hybrids (Agrisure 3122 E-Z Refuge and Genuity SmartStax RIB Complete) as compared with its use as a stand-alone rootworm product.

Producers are encouraged to consult the 2013 onTarget report that will be published later this year for a full description of the insecticide efficacy trials that were conducted across the state this past year. This on-line report also provides results from our corn rootworm trials from previous seasons. I offer my thanks to Ron Estes, Principal Research Specialist, and Nick Tinsley, Research Specialist, Department of Crop Sciences, for their leadership in the establishment of the corn rootworm trials this past season.

Mike Gray

Table 1. Preliminary Node-Injury Ratings^1,2 for Corn Rootworm Control Products in a Research Trial near Urbana, University of Illinois, 2013.

¹Node-injury ratings are based on the 0-to-3 root-rating scale developed by Oleson et al. (2005): 0.00 – no feeding damage; 1.0 – one node (circle of roots), or the equivalent of an entire node, pruned back to within approximately 1.5 inches of the stalk (or soil line if roots originate above ground nodes); 2.0 – two complete nodes pruned; 3.0 – three or more complete nodes pruned (greatest rating that can be given).

²Means followed by the same letter within a column do not differ significantly (P = 0.05, Duncan’s New Multiple Range Test.)

³Placement: T-band: insecticide applied in a 5-inch band over the planted row; SB furrow: insecticide applied through a SmartBox insecticide delivery system and directed into the seed furrow.

⁴Urbana – Planted on May 16, 2013 into an area planted to a trap crop in 2012 (late-planted corn interplanted with pumpkins). Roots were dug on July 18, 2013.

⁵Seed treated with Poncho 500, 0.5 mg a.i. per seed.

⁶Seed treated with Cruiser 250, 0.25 mg a.i. per seed.

⁷Seed treated with Poncho 250, 0.25 mg a.i. per seed.