The past few years of increased rainfall and persistent wet conditions have resulted in some rice fields that haven’t dried out for multiple years. As a result, we’ve received some calls on problematic water-dependent weeds, specifically common cattail.
Common cattail is a perennial, aquatic weed. Although it appears grass-like, it really is more like a bulrush. Common cattail is also characterized by large, creeping rhizomes which make this weed extremely troublesome to achieve long-term control.
Unfortunately, there are no great, simple options to control common cattail in rice. There are limited herbicides to suppress cattail throughout the growing season, and it will require several sequential applications throughout the season; however, this most likely will still not completely kill the weed, especially the underground rhizomes.
In severe infestations and for complete, long-term control, the best option may be to fallow the field for a year, dry it out, and dig out/remove all rhizomes from the soil.
As far as herbicide options for controlling common cattail, first and foremost it is recommended to grow a FullPage hybrid. Some previous research conducted by Dr. Bob Scott illustrated the most effective herbicide for cattail control was imazamox (Postscript). With recent changes in Postscript’s labeling, the FullPage system allows for 3 sequential applications at 5 fl oz/A.
Other herbicide options that have provided some effective control of common cattail in order of their effectiveness were: Grasp (2 oz/A) + Regiment (0.4 oz/A), Propanil (4 qt/A) + Facet (43 fl oz/A), 2,4-D (3 pt/A), and Aim (1.25 oz/A). However, these options come with their own challenges.
Grasp + Regiment and Propanil + Facet both may lead to potential rice injury through either an overload of ALS-inhibiting chemistry or delayed phytotoxicity syndrome (DPS), respectively. 2,4-D is limited to a very tight application window within our rice crop.
Aim may help burn back cattail vegetation, but as a contact herbicide, it will probably have very minimal influence at controlling cattail from a long-term standpoint.
Overall, the FullPage system with multiple, sequential applications of Postscript is the best option for controlling cattail throughout the rice growing season and may help with some long-term control.
There are a few other herbicide options that can be used to assist with control; however, they have the potential to cause rice injury. Effective long-term control will require the removal of the extensive rhizomes of common cattail.