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New weed in rice: Stinkgrass
Author: Bob Scott, Professor & Extension Weed Scientist

By Bob Scott, Extension Weed Scientist

A potential new weed in Arkansas rice has surfaced in Poinsett County.  Stinkgrass, Eragrostis cilianensis, is common throughout the lower 48 states but generally not known as a major agricultural weed in Arkansas.  In addition, it does not normally survive in flooded conditions; however, it is normally found in wetter areas along roadsides, ditches and other non-cultivated areas.

Stinkgrass, Eragrostis cilianensis.

For at least one farmer in NE Arkansas it has been observed creeping into the flooded environment of his rice fields from field edges and levees.  First brought to my attention in 2016, an initial on-farm evaluation of high rates of both Clincher and RiceStar failed to provided adequate control as did Newpath and Beyond.

Further evaluation of this weed has shown it to be extremely difficult to control with rice herbicides.  An extensive greenhouse screen revealed that only Command applied PRE, Prowl delayed PRE and RiceBeaux applied very early POST at 4-5 quarts/A were effective.

With the exception of Proviso herbicide, new chemical options soon to be released in rice were also not able to provide commercial control when applied POST, although further evaluation in the field with these newer technologies is needed.

In addition, once established it was determined that this population of stinkgrass can survive a shallow flood but not a flood that can get over the top of the pest.

Stinkgrass control with Prowl H2O PRE in greenhouse test

This work was conducted under a grant from the Arkansas Rice Promotion Board, their support is greatly appreciated.

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