The California Cotton Pest Control Board, overseer of one of the most successful biological pest control programs in American agriculture, has adopted a major change in its almost four-decade old efforts to keep the pink bollworm out of the San Joaquin Valley.
For the first time ever, SJV producers will be allowed to forego burial of shredded, uprooted cotton stalks in response to growers wanting to lower costs through reduced or minimum tillage.
“For a number of reasons, minimum tillage is going to become more prevalent in Western agriculture,” said Wally Shropshire of Blythe, Calif., chairman of the pest control board.
“If we can preserve the integrity of the pink bollworm program and help farmers reduce costs by reducing tillage, it is something we have to look at,” said Shropshire.
Shropshire said minimum tillage has proved successful on Hull Farms where he manages part of the operation.
“For four years we have been taking out third year hay stands after two spring cuttings; stubble disking it followed by a ripper/lister and planting stacked gene cotton and it has worked fine,” said Shropshire.
Hull Farms gets two cuttings of high quality spring hay from an older stand of alfalfa and still can get cotton in by mid to late April.
The cotton is stacked-gene Roundup Ready/Bollgard cotton which allows farm owner Bob Hull to control weeds with an over the top herbicide and stave off pink bollworm with the Bt gene.
Jim Rudig, director of the grower-funded pink bollworm program within the California Department of Food and Agriculture, said the pest control board and program managers considered changes in the crop destruction scenario at the request of producers who are looking at ways to reduce costs.
Relaxing crop burial rules could save up to three passes across a field.
Must still shred
Growers must still shred and uproot cotton stalks after harvest, but with a permit from their local county commissioner, they can bypass burying shredded residue.
One of the cornerstones of the 36-year-old pink bollworm program to exclude one of the world's most destructive pests from the San Joaquin Valley is creation of a host free period each year, normally about 60 days, when there is no plant material upon which the pinkie can overwinter. Pink bollworm can survive only on cotton.
Reducing tillage cost was not the only consideration in the board's decision to relax plowdown rules. “There are obvious concerns about air pollution restrictions on agriculture and by allowing growers to make fewer passes, hopefully it will have an impact on PM10 emissions,” said Rudig.
Plus, he said widespread use of Bt cotton in Southern California has lowered the threat of pink bollworms moving into the San Joaquin Valley, added Rudig.
The new regulations are not carte blanche. The rules will be relaxed on a yearly, permitted basis and any native pink bollworm finds in the reduced-tillage area will result in revocation of the permit for not only that field and section, but adjoining sections as well.
The program, funded by growers annually at $2 per bale, monitors the valley for native pink bollworm and also aerially releases million of sterile pink bollworm each year to overwhelm any native populations.
Even with 96 percent of the cotton planted in Riverside and Imperial counties is Bt cotton, the threat of pinkie establishment in the San Joaquin has not disappeared, Rudig said.
Desert trap line
“I have no doubt that if we did nothing to keep the pinkie out, a pink bollworm infestation would start in the valley,” said Rudig. Each year CDFA trappers catch native moths in SJV pheromone traps in cotton fields.
The program also continues to run a desert trap line between Southern California and the San Joaquin Valley each year, and non-sterile moths are caught there almost every year.
“Pinkies are unbelievable fliers,” said Shropshire. “They have been found as high up as 4,000 feet. Several years ago in Texas they put pinkie moths and other moths in a wind tunnel. The pinkies folded up their wings and rode the wind while other moths were obliterated.”
These native moths trapped in the desert are likely coming from “refuge” cotton required of Southern California growers who plant Bt cotton. Bt cotton growers must plant 5 percent of their acreage to non-Bt cotton as a refuge and safeguard against resistance buildup in the pink bollworm population to the Bt toxin in genetically modified cotton.
“The pinkies also are undoubtedly coming from Mexico,” said Rudig. “There are 100,000 acres of non-Bt cotton in the Mexicali Valley just across the border. Pink bollworm does not recognize the international border.”
There are no Bt, pink bollworm-resistant Acala and Pima cotton varieties in the San Joaquin because pinkies have never been an economic threat to valley cotton, thanks to the grower-funded exclusion program.
However, SJV growers are benefiting from the technology because of the buffer Southern California Bt cotton provides.
That does not mean SJV growers are not interested in the worm pest-fighting biotechnology. Over the past few years, other worm pests like armyworms have become a problem in areas of the valley. Biotechnology firms are promising soon to make available to cotton breeders genes to ward off pests other than pink bollworm. This would be of considerable interest to valley growers.
The Bt technology has dramatically reduced pest control costs in Arizona and Southern California.
“We spray very little, maybe a little thrips and lygus and that is it,” said Shropshire. Occasionally, refuge cotton is also treated for pinkies.