þ Two new herbicides on the immediate horizon for weed control in rice are benthiocarb (Bolero®) and Hydrothol® 191. Bolero® is primarily a grass herbicide and will control both barnyardgrass and sprangletop when used properly. Best results have occurred when applied postflood 10 to 12 days after seeding (when rice is in the two- to three-leaf stage and the weeds are in the one- to two-leaf stage). Significant rice injury has been noted when postseeding applications are made before rice is well rooted. Applications made 18 days after flooding were generally too late for good grass control.

þ Hydrothol® 191 has provided outstanding control of American pondweed and provides significant economic yield increases where infestations are heavy. Because American pondweed regrows each year almost entirely from winter buds, applications made in time to prevent their formation have reduced regrowth the next year.

Research has shown that rice varieties exhibit varying degrees of susceptibility to existing herbicides. As new varieties are developed they are screened against all registered herbicides before they are released. Also as new herbicides are developed they are screened against all the rice varieties being grown in California.

Main thrust of this research has been in the development of new herbicides. Several promising herbicides are under further study. An example of this group is bentazon, a herbicide showing promise for the control of broadleaved weeds including cattails. In addition, there are two herbicides that show excellent promise for controlling weeds in drilled rice, as well as four showing promise for use in water-seeded rice.

Wider use of propanil possible? Our 1974 research indicates the ground rig use of propanil might be possible as long as a distance of at least ½ mile is maintained between treated rice and sensitive prunes or almonds. We hope that this distance can be reduced by improved equipment to be used in 1975 field test work. Researchers had good drift control beyond 600 feet, with very little evidence of prune and almond tree effects beyond this. However, the distribution pattern and drop size produced by the SS Company low pressure nozzles is not as good as it should be. We hope that tests in 1975 with a deflector type nozzle with limiting orifices will improve on the drift results as well as maintain good weed control. Weed control was some 85% in the plots run this year. There appears to be no advantage to use of viscous additives on the types of atomizers that produce large drops when operated at low pressure. Tests in 1975 will feature helicopter propanil application.

þ A new chemical, bentazon, showed remarkable ability to control broadleaved weeds and cattails in a UCD experiment.