Effect of Insecticide Seed Treatment on Safening Rice from Reduced Rates of Glyphosate and Imazethapyr

M R Miller,R C Scott,G Lorenz,J Hardke,J K Norsworthy

doi:10.1155/2016/7623743

M R Miller, R C Scott + Show 3 more

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https://doi.org/10.1155/2016/7623743

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Abstract

Field experiments were conducted in 2013 and 2014 to evaluate the effect of insecticide seed treatments on exposure of young conventional rice to reduced rates of glyphosate and imazethapyr. During the two-year study, “Roy J” rice seed was treated with CruiserMaxx® Rice, thiamethoxam plus fungicide, or a fungicide-only treatment. Subsequently, glyphosate (Roundup PowerMax®) at 39.42, 78.76, or 157.54 g ae/ha or imazethapyr (Newpath®) at 4.39, 8.74, or 17.49 g ai/ha was applied at the 2- to 3-leaf growth stage of rice. Results in 2013 indicated that rice plants from seed treated with CruiserMaxx Rice exhibited significantly less injury 1, 3, and 6 weeks after either imazethapyr or glyphosate was applied in comparison to the plants having fungicide-only treated seed. The addition of an insecticide seed treatment also resulted in higher yields when both herbicides were applied compared to the fungicide-only seed treatment receiving the same herbicide treatments. In 2014, an overall decrease in injury from both herbicides was observed when rice seed was treated with CruiserMaxx Rice compared to receiving a fungicide-only seed treatment. Significant yield loss from low rates of glyphosate or imazethapyr was not observed in 2014, with or without a seed treatment. Based on the positive effects observed from the CruiserMaxx Rice seed treatment in reducing injury and maintaining rice yields, the insecticide seed treatment appears to provide some safening to rice against low rates of glyphosate and imazethapyr.

Highlights

In 2014, Arkansas led the nation in rice production with approximately 50% of the rice acreage planted [1]
In 2013, 1 weeks after the herbicide treatment (WAT), both glyphosate and imazethapyr caused visible injury to the rice plants from the fungicide-only treatment exhibiting 24% injury and significantly less injury (14% injury observed) when the rice was treated with the thiamethoxam-containing insecticide seed treatment (Table 1)
As reported by previous insecticide/herbicide interactions [9], an overall safening effect was observed with less visible injury occurring 1 WAT in 2013 in plots containing the insecticide seed treatment compared to those without an insecticide seed treatment

Summary

Introduction

In 2014, Arkansas led the nation in rice production with approximately 50% of the rice acreage planted [1]. The rice acreage remaining is planted to rice cultivars which do not contain the imidazolinone resistance trait and cannot tolerate applications of imazethapyr or imazamox. Non-Clearfield rice acreage is susceptible to injury should imazethapyr or imazamox be applied to the field through tank-contamination, drift, or accidental application. Arkansas consistently produces around 1.4 million of hectares of soybean and corn with a majority of acreage planted to glyphosate-resistant varieties (Roundup Ready, Monsanto, St. Louis, MO) [1]. MO) for weed control in these production systems It is not uncommon for corn and soybean fields to be located nearby or adjacent to areas where rice is grown indicating that the potential for rice exposure to glyphosate through tank-contamination and/or drift exists

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