Pesticide purity establishes foothold

Agricultural pesticides that are only toxic to targeted pests, weeds and diseases have gained a strong foothold and their use is rapidly expanding.

A leading supplier of the magic compounds that are created when certain plant materials rot or are encouraged to decompose says they amount to 38 percent of the pesticides that farmers apply. And she predicts continued rapid growth and acceptance.

Organic growers were the first to embrace these relatively new biopesticides, but conventional farmers are jumping on the non-toxic bandwagon like codling moths to an apple orchard. They haven't enjoyed using the much-criticized synthetic chemicals for pest control, but most felt they had no choice — until recently.

The leading supplier is a company in Davis called Marrone Bio Innovations. Its CEO is Pam Marrone, a veteran of 20 years with Monsanto Chemical Co., a major agricultural chemical supplier. Monsanto's Roundup weed killer has led to significant, but often controversial, improvements and changes in farming practices.

Not surprisingly, one of Marrone's first products controls many of the same weed species as glyphosate (Roundup's generic name).

One of the first biopesticides to gain wide acceptance is called Serenade, a compound to control mildew on grapes and some other fungi. Soon after it was established, Marrone began searching for non-toxics to control nematodes, insects and invasive species. An early find was a material that controls two types of mussels that are clogging the Colorado River and other important waterways.

Some of the materials she supplies are tonics for plants that help them develop induced systems resistance (ISR). Others help the plants increase their immunity to a range of illnesses and deficiencies.

When Marrone spoke to an organic production seminar in Modesto recently, Western Farm Press was there. The magazine said she told the group that biopesticides can be developed and brought to market for far less than the $200 million it takes to develop and gain registration for a typical synthetic pesticide.

The magazine reported her comment that 80 percent of the biopesticides now available are used in conventional agriculture, rotated and tank-mixed just like any other product.

The definition for biopesticides given by the Environmental Protection Agency excludes chemicals that have direct modes of action against an insect's nervous system, even if the material is natural. Such a narrow interpretation caters to growers who specify their products to be organically grown.

While that definition is somewhat limiting, Western Farm Press reported that most biopesticides have complex modes of action, which makes it hard for pests or pathogens to develop resistance to them. These safe compounds also allow early re-entry into treated fields and present no air or water pollution issues.

Marrone says that biopesticides are most often used because of environmental safety. And they are avoided because of a perception that they might not be as effective as synthetic chemicals.

However, Marrone points to surveys about biopesticides taken in 2003 and 2008. The latest showed that the number of California growers and pest control advisers with positive perceptions grew significantly between the dates of the two surveys.

So environmentalist detractors of farmers are losing a primary target. You can bet they will find at least one substitute.

Don Curlee is an agricultural writer based in Clovis. His column appears biweekly. E-mail him at agwriter1@sbcglobal.net.