The chemical injury caused by 60% butachlor EC in Hunan Province

Recently in Nan County, Yiyang City, Hunan Province, many cases of chemical injury were caused by 60% butachlor EC, which is a pre-emergence herbicide, in single-season direct-sowing rice fields. According to the investigation, the area using 60% butachlor EC was 800 ha in total, of which 140 ha that was allocated to rice crops was so seriously damaged that the seedlings were dead and needed to be recultivated and reseeded. Another 120 ha of rice was damaged moderately, which meant that the spacing of the seedlings needed to be adjusted and management needed to be enhanced. This is the most severe chemical injury incident, with the largest scale and the most serious degree of damage, within the last decade.
60% butachlor EC is effective on weeds in rice fields and has low costs. However, it has strict requirements on application technique, because under the conditions of uneven field surface, inappropriate management or abnormal climate, chemical injury can easily occur.
According to the investigation, there was no obvious chemical injury in rice fields which used 60% butachlor EC before 18 May when the weather was fine. The rice fields that used 60% butachlor EC from 19 May to 24 May were exposed to cold and rainy weather, which led to slower growth rates for rice seedling, declining chemical tolerance ability and severe chemical injury. If it rains heavily two to three days after the application of 60% butachlor EC, the chemical injury will be more severe. This is especially obvious on extensively cultivated rice fields with uneven surfaces and no ditches and where drainage is poor.
Experts give three suggestions on how to prevent chemical injuries resulting from the use of 60% butachlor. Firstly, carry out intensive cultivation. It should be ensured that field compartments are separated and ditches are dug, field surfaces are even with no plashes in three to five days after pesticide application. Secondly, soak seeds to hasten germination. Thirdly, apply 60% butachlor EC according to the weather conditions. The pesticide should be applied if the forecast for the three following days is for fine weather. Fourthly, utilize the pesticide according to tested methodology.