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Williamson
County
Result Demonstration Report 
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Evaluation of Selected Insecticides/Seed Treatments For Control Of Mexican Corn Rootworm
Cooperator:
Bob Avant
Dale A. Mott
EA-IPM
Ron Leps
Extension Agent-Agriculture
Hutto, Williamson County, Prencinct #4
SUMMARY: Four different corn soil insecticide/seed treatments were evaluated in a field of 5th year corn farmed by Robert Avant. Corn treated with Aztec® 2.1 G, Force® 3G or Prescribe® had the least amount of corn rootworm damage. Root damage in corn treated with Counter® 15G was not significantly different from damage in untreated corn. Only corn treated with Prescribe® yielded significantly more than corn treated with Counter® 15G or left untreated.
OBJECTIVE: The Mexican Corn Rootworm (MCRW) is a serious pest of corn in the Central Texas area. As more continuous corn and sorghum are being grown in Williamson county, the potential for this pest to cause severe economic damage will increase as its population increases. MCRWs are especially a problem in fields that have had continuous corn for three or more years, although there is a potential for fields of second year corn to be completely destroyed even with the use of full label rates of soil insecticides.
Therefore, the objective of this trial was to evaluate selected soil insecticides for control of Mexican corn rootworm (MCRW) in a field where corn has been grown without rotation for five years.
MATERIALS & METHODS:
On February 25, 2001, a corn soil insecticide evaluation was established in a field just south of Hutto in Williamson County, TX. The field had been in corn for the four previous years. The field is farmed by Mr. Robert Avant. Plots were 8 rows wide (38" rows) and 200 ft in length. Each treatment was replicated 3 times. A White 6700 8-row planter was used to plant the plots. Soil temperature was about 60 F. The variety of corn was DK 668.
The root ratings were performed on May 24. Roots from 8 plants per plot were dug up and rated using the Iowa Root Rating Scale. The scale ranges from 1 (no noticeable feeding damage) to 6 (three or more full nodes of roots pruned). The plots were hand harvested on August 1 by taking 2 , 1000th ac (13'8") samples from each plot corn was shelled on a small corn sheller and the samples were weighed to determine yield.
RESULTS AND DISCUSSION:
The Force® 3G, Prescribe®, and Aztec® 2.1G treatments provided a significantly lower root damage rating than did the Counter® 15G and untreated check (Table 1). In addition, the Prescribe® treatment (99 bushels/ac) significantly out yielded the Counter® 15G and untreated check with yields of 77.8 and 72.3 bushels/ac, respectively.
Table 1. MCRW Root Ratings and Yield. Hutto, TX, 2001
| Treatment | Rate | Mean Root Rating | Yield (Bushels/Ac) |
| Force® 3G | 4.3 lbs/Ac | 2.83 b | 78.6 ab |
| Prescribe® | 1.34 mg/kernel | 2.83 b | 99.0 a |
| Aztec® 2.1G | 5.8 lbs/Ac | 3.39 b | 86.4 ab |
| Counter® 15G | 6.8 lbs/Ac | 4.69 a | 77.8 b |
| Untreated | - - | 5.03 a | 72.3 b |
| LSD | 1.04 | 20.4 | |
| P>F | 0.026 | .038 |
Harvested plots on August 1
Means within a column followed by the same letter do not significantly differ
This trial demonstrates that Prescribe® appears to be a viable alternative in reducing MCRW damage in fields of continuous corn. However, because of the lack of chinch bugs and southern corn rootworm data, additional studies need to be established to determine the level of controlthat Prescribe® provides on these pests. Also, this study again demonstrated that the Force® 3G and Aztec® 2.1 treatments provide good protection from the MCRW.
ACKNOWLEDGMENTS:
Appreciation is expressed to Robert Avant for the use of his land and for the time and effort put into planting and keeping up this study. Also appreciation is also expressed to American Cyanimid, Bayer Corporation, Syngenta, and Gustafson for their financial and product support.
