Rice Disease Research and Management, 2021

 

Luis Espino, UCCE Farm Advisor, Butte and Glenn counties

This project seeks to consider three things in the management of disease in California rice:

• Use of fungicides to manage • stem rot, aggregate sheath spot, and kernel smut.

• The susceptibility of California varieties to stem rot, aggregate sheath spot, and kernel smut, while exploring their effect on yield and quality.

• Monitor the response of the blast resistant variety, M-210, to blast epidemics in the field.

Evaluation of fungicides

Results from this year’s trial confirm that azoxystrobin (Quadris) applied at mid boot or early heading can reduce the severity of stem rot and aggregate sheath spot. Trifloxystrobin (Stratego) applied at the mid boot stage also reduced the severity of the diseases but was not as effective as azoxystrobin. The fungicide WE2052-1 also reduced the severity of the diseases when applied at propanil time; however, the reduction was not as high as with azoxystrobin applied at boot or heading.

Susceptibility of California Varieties

For stem rot, all varieties tested benefited from the application of azoxystrobin at the early heading stage, resulting in a reduction of disease severity and a yield increase. Disease severity varied across varieties, with long season varieties showing lower severity than short season varieties.

For aggregate sheath spot, disease levels were low. However, variety CM-101 responded to the application of azoxystrobin at early heading with a yield increase. Variety A-202 had the lowest disease incidence and varieties CM-101, S-102, M- 105, and M-206 the highest.

During crop year 2021 very little blast developed in the Sacramento Valley. Four M-210 fields were monitored during the season, but no blast symptoms were observed.