Tuesday, June 15, 2010

Herbicide Injury Appears Again

I have looked at a couple of fields that have experienced Permit injury similar to what we have seen in the past.  The common symptoms include bright, distinctive yellowing about 7 days after flooding similar to what would be expected with sulfur deficiency, some stunted growth but not always severe, typically occurs on silt loam soils with high soil pH, and normally recovers within about 2 weeks. The yellowing is similar to what is observed with clorimuron (Classic, Canopy XL) carry-over into rice. The yellow color also resembles Newpath injury. All of the compounds are similar and have similar modes of action. Plant tissue analysis normally suggests that the plant nutrient status is normal (i.e. nothing is deficient). A few years ago, we were able to observe the injury in sprayed and unsprayed areas of a field. This allowed us to verify our suspicions.

The green rice in the above photo is an area that was not sprayed and obviously resulted in no rice injury but also no nutsedge control. While the rice seems to be severely affected, little or no yield loss has been observed in the fields where this has occurred.

While this may explain the yellowing in some fields, there are other problems that may be occurring. I am aware of a couple of fields in the past that have similar symptoms and Permit was not applied to the fields.

Draining the fields has been a common practice to get the field to recover. Various fertilizers have also been used with ammonium sulfate being most common. While the fertilizer is only going to correct nutrient deficiencies that may result from the rice being stressed, the nitrogen may help encourage the crop to recover more quickly.

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