Cotton plants compensate for early season losses to insect pests, but how well the plant compensates may depend on the season and the management system.
A panel of cotton researchers addressed cotton's potential to rebound after early-season stress at the recent World Cotton Research Conference in Lubbock, Texas.
Tom Kerby, Delta and Pine Land Company, Scott, Mississippi, said that agronomists and entomologists sitting in the same room and discussing the subject is in itself a relevant issue.
“Back 25 or 30 years ago we would not have had this type discussion between entomologists and agronomists,” Kerby said. “(The two disciplines) had different views until about 10 or 15 years ago.”
Then both decided the best course was “to look at the plant.”
Kerby said anyone who would guess at how much a cotton plant could recover following stress would “always underestimate how much it would compensate.”
He said integrated pest management (IPM) may have initiated some of the changes. “IPM is plant based, but early in the 1960s the practice was different. Farmers used mostly relatively indeterminate varieties; they had boll weevils and bollworms; and they did not have plant growth regulators. IPM followed something of a scorched earth policy.”
With those aggressive techniques, he said, “no one knew that cotton could compensate a great deal. Today we know the cotton plant has significant potential to compensate and to maintain both yield and quality.”
He said the quest for early boll retention sometimes can be misleading. “Often these early bolls are not picked,” he said. “In some areas, boll rot takes those lower bolls. But there is no one-size-fits-all program. Cotton farmers in the High Plains, for instance, will have less worry from boll rot than will farmers in South Georgia. Cotton has a tremendous ability to compensate, but a lot depends on environment and management.”
M.N. Parajulee, Texas A&M researcher, said in some cases when manually removing 100 percent of the cotton plant's squares until first bloom the plant may overcompensate for the loss.
He said tests with released Lygus bugs showed cotton's ability to compensate for early loss varied with the season and management system. “The cotton plant has significant potential to compensate with the right conditions.”
Lewis Wilson, with Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO), said a cotton plant's ability to compensate for early fruit loss from pests “may provide an opportunity to reduce spraying.” In some cases bolls fall off following damage and “immediately are replaced, making up for potential yield loss.”
Lewis used both caged mirids and injections (of a chemical that mimics mirid injury). “Injection injury was more severe,” he said. Compensation for injury inflicted later in the season was less.
Tina Teague, Arkansas State University, compared compensation of low and high vigor cotton.
“With precision agriculture capabilities, growers want to make decisions everywhere possible,” Teague said.
The potential may exist to eliminate or reduce insecticide applications in poor yielding areas. “Farmers may save money by changing management in low vigor zones.”
The season plays a crucial role. In dry years, low vigor, non-irrigated zones showed little difference in compensation. The bugs were not as crucial a factor as the weather.
“In 2006, we had good conditions for plant bug survival but low vigor areas did not compensate.”
Jane Pierce, New Mexico State University, said determining crop value and evaluating economic loss to bollworms is difficult.
“The value of a lost square is not equal to the boll it may have produced,” she said. Removing bolls resulted in yield loss. But she recorded a high rate of compensation for lost squares. “It may be difficult to justify late-season square protection. Late season protection of bolls is more important.”
Kerby said understanding the plant has become a critical factor in managing a cotton crop. “Plant monitoring has brought disciplines together,” he said. “First, look at the plant.”