Andy Kleinschmidt, Extension Agriculture and Natural Resources Agent
Gary Prill, Farm Focus/Research Coordinator
To evaluate corn-yield benefit from using ProShield seed-coating technology in comparison to conventional granular insecticides in continuous corn.
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Two granular insecticides, one untreated check, and a ProShield seed-coating treatment were replicated five times in a randomized complete block design. Each plot contained six rows and was 450 feet long. The study was planted using a John Deere 7000 Max Emerge six-row planter. The granular insecticides were applied in a T-Band at the full labeled rate. One treatment contained corn with a Force ST seed-coating treatment (ProShield) and was planted without the use of any additional granular insecticide. Root ratings were taken on July 18 by digging and washing five root systems from each plot and rating those root systems using the Iowa Root Rating Scale.
Harvest populations were evaluated by counting the number of plants on each side of a 17.5-feet tape at three different locations in each plot. The average of the number of plants counted per 17.5 feet was converted to plants per acre. Each plot was harvested and then weighed by a calibrated weigh wagon, and grain yield was adjusted to 15% moisture.
Root rating, harvest population, and yield means for each treatment are given in the following table:
| Treatment | Rate per 1,000 row feet |
Root Rating | Harvest Population |
Yield |
| – plants/A – | – bushels/A – | |||
| Lorsban 15G | 8.0 oz | 2.36 a | 26,100 | 112.2 |
| Force 3G | 4.0 oz | 2.40 ab | 26,300 | 114.2 |
| ProShield | NA | 2.64 bc | 26,900 | 114.7 |
| Check | NA | 2.88 c | 25,700 | 120.2 |
| LSD (P = 0.05) | 0.27 | NS | NS | |
| CV (<15% is credible) | 7.6% | 2.7% | 7.2% | |
| Means in a column followed by the same letter are not significantly different at P = 0.05.
NA = Not Applicable, NS = not significant. |
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Rootworm pressure in this study did not reach a level of damage that is considered economic. A root rating of 3.0 or higher frequently indicates the beginning of economic loss. To prevent yield loss, an insecticide should protect the corn roots so that no more than approximately one-third of a node of roots is destroyed by western corn rootworm larva. In this study, the check strips had an average root rating of 2.88. The results of this one-year study indicate that ProShield root ratings were not significantly different from that of the untreated check. The root ratings for the Lorsban and Force treatments were significantly lower than the untreated check; however, there was not a corresponding significant difference in corn yield. Harvest population and yields were not significantly different among the four treatments, as indicated in the table above. Although the check treatment yield appears greater than the other treatment yields, it was not statistically different due to variation within the replications.
The seed-coating approach is convenient, environmentally sound, and user-friendly as compared to conventional granular insecticides. However, emphasis must remain on selecting products based on performance. Two insecticide performance indicators that producers can use are root ratings and yields. When evaluating insecticide performance, it is important to evaluate check strips with moderate to heavy rootworm pressure established in the same fields with a given insecticide. Those products that deliver the best rootworm control should be considered for those areas where rootworm damage is common or anticipated.
The authors wish to express their appreciation to Novartis for donating material used in this study.
For additional information, contact:
| Andy Kleinschmidt | Gary Prill |
| Agriculture and Natural Resources Agent | Farm Focus/Research Coordinator |
| OSU Extension, Van Wert County | OSU Extension, Van Wert County |
| 1055 South Washington Street | 1055 South Washington Street |
| Van Wert, OH 45891 | Van Wert, OH 45891 |
| 419-238-1214 | 419-238-1214 |
| kleinschmidt.5@osu.edu | prill.1@osu.edu |