The economic incentive for producing weed-free alfalfa hay is growing right along with the burgeoning California dairy industry.

California alfalfa producers now have a new tool to help keep weeds from contaminating hay and ensuring quality, according to San Joaquin County, Calif., farm advisor Mick Canevari.

Canevari detailed research he and other farm advisors have done on the new broadleaf weed control herbicide Raptor from BASF Corp. at the recent California Weed Science Society meeting and the Western Alfalfa and Forage Conference.

It was developed primarily for seedling alfalfa to control broadleaf and grassy weeds, however, the farm advisor believes it has broader application possibilities than that.

“Raptor is in the same chemical family as Pursuit and will become the primary herbicide choice for alfalfa growers in years to come,” said Canevari.

“Raptor controls a similar spectrum of broadleaf weeds as Pursuit but many more grass weeds. Controlling a broader spectrum of weeds can eliminate the need for combining two herbicides together,” he added.

Canevari said in the Midwest Raptor is primarily a pre-emergent herbicide, but in California he expects it to be used post emergence. “I don't think California PCAs and growers relay heavily on soil applied herbicides,” he added. Most use post-emergent materials.

Weed-free pays

“Developing a new alfalfa field without weeds pays dividends from the beginning and continues throughout the life of the stand,” he said.

Herbicides are applied to 75 percent of newly planted alfalfa in California. Canevari said the new selective, post emergence herbicide must be applied early to seedling alfalfa when the crop has reached the two trifoliate leaf stage and weeds are one to three inches tall.

“Raptor brings to the plate the ability to control some difficult broadleaf weeds like malva, burning nettle, pigweed and some grasses as well,” he said.

However, Canevari said perhaps just as important using it on seedling alfalfa is its fit for in-season use, particularly for control of lambsquarter, pigweed and as well as grasses.

What makes it fit well in-season is its 20-day pre-harvest interval. Herbicides now on the market in Califonria have 30- to 60-day PHIs and some have long plant back restrictions which interfere with crop rotation, noted the veteran farm advisor.

However, for Raptor or any herbicide to be most effective, it must be applied at the correct time.

“Most people talk about applying herbicides when the plants are actively growing and small. However, green weeds do not mean plants are not stressed,” he said.

Ample moisture

That is why he recommends making sure there is good soil moisture before applying the herbicide. “That is one of the real keys to getting good control. Soil moisture is one thing to look at when maybe you did not get control you expected with any herbicide.”

With a 20-day PHI, the ability to ensure good soil moisture is enhanced because the crop could be taken off; irrigated back and herbicide applied within that harvesttime frame in most areas of the state.

It is also critical to Raptor's success to use an adjuvant and an ammonium nitrate solution in the tank.

“Ammonium nitrogen solution can be a real benefit with this product. When you have less tolerant weeds, this can make the difference in getting decent weed control and not. It can increase weed control 10 to 15 percent when an ammonium nitrogen solution is added,” he concluded.

e-mail: hcline@primediabusiness.com