- Author: Larry Godfrey
Large RWW flight at RES (Biggs, CA) night of April 30. We got over 2100 RWW which exceeds the total number captured the entire season in 2011 (a record low with only 415) and rivals the seasonal total for any year of the last 10 (except 2009 which was over 6000). The night of April 29 appears to have over 500 adults as well (have not counted them yet). The environmental conditions for flight did not appear ideal during those nights but I guess it was “good enough”. Am I predicting a heavy weevil year? It seems the infestation patterns are very localized now as opposed to coming from long-range flights so a prediction is hard to come up with. But this pest is certainly “out and about” and waiting for flooded conditions.
- Author: Luis Espino
I was looking for weevils today, so I visited a field with a history of weevil problems. The field was seeded 3 days ago, and there were no plants (rice or weeds) in the field yet. Levees were clean, the borders were weedy.
First, I looked at the grassy weeds around the edges of the field, and found some fresh feeding scars. Evidence that weevils were around.
Then I looked at some of the weeds that ended up under water after the flood.
After a few minutes searching, I found some weevils.
Rice water weevils come out of their overwintering sites in March-April and start feeding on grassy weeds. This allows them to regenerate their wing muscles and fly to flooded rice fields. Water seems to be the main attractant. Once there, they can feed on grassy weeds until rice seedlings start developing.
Looking for feeding scars and weevil adults will help you decide if you need a treatment. Remember that weevil infestations tend to be higher near weedy borders and levees.
While you are out there, also look for midge larvae and tadpole shrimp. Inspect the seed for midge injury and silken tubes. Tadpole shrimp eggs hatch after 3 days of flooding, but young tadpole shrimps are very small and hard to see. You will start seeing tadpole shrimp adults 8-12 days after flooding.
For more information and management options, consult the UC IPM Management Guidelines: Rice.