Rats in rice

We have had some interesting calls lately concerning issues we do not usually see in the fields. We have received calls about small circular areas with “snipped” rice in fields west of I-5. 

Picture1
 
Picture2

The small circles looked VERY similar to those created by blast; however, we saw no lesions or symptoms of blast, and the yellowed plants had been chewed near the base of the plant.

As we stood at the edge of the field, a quiet rustle alerted us. We spotted a small, brown rodent slipping into the field, likely a Norway rat based on the length of the hairless tail, which was shorter than the length of the rodent's body.

Picture3

 

 

 

 

 

 

 

 

Picture4

The Norway rat is probably the most serious vertebrate pest of rice and it can feed throughout the season, from seedling stage to ripening grain. However, we have not seen a large amount of damage from these rodents, indicating that the level of infestation is not high enough to warrant treatment.

Bait boxes, zinc phosphide, and aluminum phosphine tablets are options for control (2024); however, there are additional requirements for these besides an applicator license or certificate. Zinc phosphide and aluminum phosphine are CA Restricted Materials and an additional Burrowing Vertebrate Fumigation qualification is required for aluminum phosphine use. If conditions suggest that rodenticide is the best option, the rodenticide and application method should be chosen with regard for potential non-target hazards. Consult your Agricultural Commissioner for specific information.


By Sarah Marsh
Author
By Taiyu Guan
Editor - Assistant Specialist
By Consuelo B Baez Vega
Editor - Rice Junior Specialist

Attached Images: