Two developments growers and pest control advisors always look forward to are new pest control tools and new uses for existing pesticides. New chemicals for weed and insect control are in the registration pipeline and a commonly used herbicide is awaiting a supplemental label for one of alfalfa's more persistent weed pests.
If the registration process goes as anticipated, growers should have a new “reduced risk” herbicide this fall that has performed well in University of California trials. Raptor (imazamox) is related to a commonly used herbicide, Pursuit, but with significant differences in the spectrum of weeds that it controls. According to information prepared by two UC farm advisors for the 2000 California Weed Science Society meeting, Raptor's “primary advantage is that it controls a broader spectrum of weeds. This is a major advantage as the common, currently registered postemergence herbicides control grassy weeds or broadleaf weeds but not both,” they pointed out.
Other advantages cited for the BASF product were a shorter residual than Pursuit and a much lower use rate. The farm advisors reported that Raptor is more effective than Pursuit against fiddleneck, but less effective for red maids control. If prickly lettuce, sowthistle, common groundsel and lambsquarter are present, the herbicide will “likely have to be tank mixed.”
Earlier in the year a grower member of CAFA asked for information on dodder control. Relief is on the way in the form of a pending supplemental label that BASF has requested for Pursuit. Postemergence trials conducted by San Joaquin County Farm Advisor Mick Canevari showed a high degree of suppression at a use rate of 0.094 pounds of active ingredient per acre.
The herbicide suppressed dodder by 94 percent when an evaluation was made 30 days after treatment and by 79 percent at 60 days after application. Hasten and UN 32 were tank mixed with the herbicide at rates of one and two quarts per acre, respectively. Pursuit had enough effect on dodder to prevent seed production, the key to long-term management.
Another promising development for alfalfa pest control programs is a selective, broad-spectrum insecticide that will help combat a growing armyworm problem. In April, DuPont submitted a petition for tolerance to the U.S. EPA for Steward (indoxacarb).
Many California cotton growers are familiar with the insecticide from last year's Section 18 registration for armyworm control. It received EPA registration for cotton earlier this year and will hopefully get regulatory approval for alfalfa in time the 2002 use season. Steward has a unique mode of action and low impact on beneficial insects, making it a good fit for resistance management and IPM programs. A review of data from last year's Section 18 for cotton showed top-notch armyworm control and an effective residual, a welcome development for alfalfa growers who are reporting multiple applications of currently registered insecticides to get effective control of the destructive insect.
Besides worms, Steward also controls alfalfa weevils and suppresses lygus bugs. The manufacturer only has limited data on control of the granulate cutworm, a major problem for growers in the low desert who are using pyrethroids. More trials will be conducted and if initial results are repeated in future research growers will have a selective material to combat a serious pest.