Combined with diverse cultural practices, this can mean very different levels of threat and ways of countering it. The rice water weevil is native to U.S. wetlands and found as far north as Minnesota, but it crossed the Rockies to California only with human help. In the last few years, rice farmers have had to make big changes in how they keep rice water weevils from gnawing the roots off young rice. Just last year, California producers had the last Furadan for direct control of the damaging larval stage. Now you have to decide whether to treat seed with Icon long before weevils even emerge or plan another defense.
Timing is crucial.
Entomologists are still experimenting with how to predict populations of larvae in a field before the adults begin to lay eggs. You can choose Karate to kill adults before they reproduce, or choose Dimilin, a growth regulator that prevents eggs from hatching. Karate can go on from seven days before to seven days after permanent flood, says Steve Harrison, Syngenta technical crop manager, with any herbicide application. Miss the application window, and you miss control, although draining can reduce populations. Here s what state specialists are saying.