While all the new products hold promise for improving weed management in rice, they add to the puzzle of information needed to use them safely and efficiently. Thus, it will be important to know the behavior of each herbicide in the plant and the environment. Most of the newly introduced herbicides are somewhat limited in the spectrum of weeds controlled, requiring the proper selection either alone or in combination to give adequate weed control. The weed spectrum for the herbicides available for the 1999 season is shown in Table 2 and those expected by 2002 in Table 3. Potential weed control given in the tables is based on both company and UC Davis research and represent the control that could be consistently expected of a particular product, assuming that the weed species are not resistant.
Light is required because propanil blocks photosynthesis.
For best control, carefully read and follow the label which will state the rates, adjuvants, combinations and other requirements of the product. By mixing and matching the herbicides in Table 2, a complete spectrum of weed control may be possible. However, in addition to the weed spectrum, it is important to know how the herbicide is taken up by the weed, if it is translocated in the plant, the range of application timings for weed control and crop safety, if the herbicide has residual activity and whether or not the weeds are resistant. Tables 4 and 5 provide additional information on the behavior of current and future herbicides respectively. However, Ordram, Bolero, Abolish, Londax and Shark have soil activity.