Palo Verde Valley cotton acreage is expected to be down a bit this season, but not significantly, predicts Michael Rethwisch, University of California Cooperative Extension farm advisor in the Southern California desert valley.
Producers have done relatively well the past two seasons, especially in 2000 when yields of more than five bales were common. Last year yields for long-season cotton were 4.0 to 4.5 bales and for those who cut the crop off in August yielded 2.5 to 3.0 bales, according to Rethwisch. Producers exited early likely went into fall-seeded alfalfa or melons.
“You never expect a 2000 to happen again. The weather was more like the San Joaquin Valley and was extremely mild in the summer,” he explained. “Last season was more typical, but growers here did fairly well with yields and quality.”
Long-season cotton has returned to the desert, thanks to the introduction of genetically modified cotton containing the Bt gene to ward off pink bollworm. Before Bt cotton came in, it had become economically impossible to grow long-season cotton because of insect control costs.
However, one of the top yielding cottons not only in the Palo Verde Valley, but Imperial Valley as well as Central Arizona has been a non-transgenic.
Deltapine 565, a full-season variety topped Rethwisch's yield trials in 2001, outyielding eight other varieties in the trial, all transgenic either Bt or herbicide resistant. The conventional variety yielded 2,167 pounds per acre (harvested Jan. 11) and the micronaire was within the premium range.
“We had a good micronaire year last season overall,” added Rethwisch said.
Among top five
The non-transgenic variety ranked in the top five in yields in all but one of the trials in Central Arizona. It also had the highest quality. It was the longest cotton in all the trials with fiber strength of no less than 27.17 grams per text. Most of the readings were 29 or higher. It had no micronaire readings above 5.0 in all its trials.
“The variety has been very consistent in the desert and has allowed growers to make money with full season cotton without spending a lot of money on pest control,” said Rethwisch.
It is benefiting from the Bt cotton, which has reduced overall numbers of pink bollworm not only in the desert, but in Mexico as well. “More Bt cotton is being grown in Mexico now and that has reduced the pink bollworm fly-ins from the Mexicali Valley we normally see in July and August,” said Rethwisch.
Controlling pink bollworm using Bt technology has also reduced lygus pressure, even with an abundance of alfalfa in the area.
“They have lygus problems in Central Arizona, but that has been associated with alfalfa seed production,” explained Rethwisch.
“Here in the Palo Verde Valley it is all for hay. Without pink bollworm pressure and less spraying, we are preserving the beneficials in the cotton to control lygus,” Rethwisch said.
Plus, alfalfa cutting schedules are relatively short early in the year to gain dairy quality hay and that does not allow lygus to mature and move beyond the alfalfa, he explained.
“We obviously still monitor for lygus in cotton and try to use soft materials when treatment is warranted,” he said. Silverleaf whitefly continues to pose a threat, but the whitefly growth regulators continue to work well. “They have been wonderfully effective here in cotton and melons,” he said.
California's desert cotton growers use University of Arizona lygus monitoring guidelines rather than those for the San Joaquin Valley, said Rethwisch. “When we sample, we separate the nymphs and adults and make decisions on treating based on utilizing both counts,” he said.
“Bt cotton has made a big difference in how we grow cotton — both conventional and transgenic,” said Rethwisch. “We can grow long-season conventional cotton again. If we see pinkies, we can treat with non-Bt materials and still be OK.”
With cotton prices at historical lows, the economical viability of full-season cotton could not be more important.