Rice Water Weevils densities in Furrow Irrigated Rice

Read Kelly, graduate student under the direction of Dr. Jeff Gore, has been investigating the relationship and densities of rice water weevils in furrow irrigated or row rice.  During 2017 and 2018, Read conducted rice water weevil studies on eleven “on farm” sites across the Delta.  Each location had a furrow irrigated field compared to an adjacent conventional flooded field utilizing the alternate wetting and drying irrigation method.  As stated in previous articles ( https://www.mississippi-crops.com/2019/03/29/furrow-irrigation-rice-yield-variations/ ), furrow irrigated rice fields are actually three sub fields.  The top one third is the driest, the middle is similar to the optimized AWD treatments (soupy wet but never dry), and the bottom one third resembles a continuous irrigated field. Read collected core samples for water weevil larvae in each of the furrow irrigated zones as well as the conventional AWD comparison field.  Presented are Read’s results.

1. Rice water weevil densities were moderate and increased each week in the flooded portion of the fields.
2. Rice water weevil densities were similar in the conventional field and the flooded lower one third of the furrow irrigated field.
3. Rice water weevil densities were the lowest the the top two thirds of the furrow irrigated fields.
4. Overall rice water weevil densities were lower in the furrow irrigated fields compared to the conventional AWD comparison

This study suggests that growers could adjust their management style for rice water weevils in furrow irrigated fields.  In general, insecticide seed treatments such as Cruiser or Nipsit are still recommended across the whole field, especially in fields that have had a history of other pests such as chinch bugs. Foliar applications targeting rice water weevil adults can usually be confined to the lower third of row rice fields where rice water weevil densities will be greatest.

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