How much have seedling diseases cost cotton farmers over the years? With the help of the Internet, growers can find good, science-based estimates for losses for most of the last 50 years, thanks to the work of a group of dedicated Extension and university researchers.
“The Cotton Disease Council is the oldest of the Beltwide Councils,” says Don Blasingame, a consultant and retired Extension plant pathologist with Mississippi State University. “Our group has been working together since 1952.”
Speaking at a recent meeting, Blasingame talked about the Disease Council's nearly 50 years of seedling disease loss estimates, compiled by members of its Cotton Disease Loss Estimate Committee. Reports for the years 1952 to 1998 are available on the National Cotton Council's Web site at http://www.cotton.org/cf/seedlings/losses.cfm.
According to the report for 2001, U.S. growers lost an estimated 704,639 bales or 2.71 percent of the crop to seedling diseases. That's just below the Beltwide average annual yield loss for the 47 years of 2.85 percent.
“We estimate that 2.2 million bales — or 10.46 percent of the crop — were lost to all of the plant diseases and to nematodes in 2000,” said Blasingame, said. “In 2001, the losses totaled an estimated 3.4 million bales or 12.62 percent of the crop.
“So diseases and nematodes are doing their best to help us reduce the carryover of cotton,” said Blasingame, who chairs the Cotton Disease Council. (Blasingame and Mukund V. Patel, retired Extension plant pathologist at Mississippi State, compiled the latest reports.)
As in most years, the seedling disease losses varied widely from state to state, depending on weather conditions and planting practices. In 2001, Tennessee suffered the highest estimated loss of 8.5 percent, while Arizona, New Mexico and Virginia reported the lowest at 0.5 percent.
For the other Mid-South states, Arkansas and Louisiana reported losses of 4 percent; Mississippi, 2 percent; and Missouri, 1 percent. All together, the Mid-South states lost an estimated 318,501 bales of cotton to seedling diseases in 2001, up from an estimated 218,332 in 2000.
These are some observations from reports compiled from by the Cotton Disease Council over the years:
- The highest yield loss to cotton seedling diseases was 4.03 percent in 1966.
- The lowest yield loss to cotton seedling diseases was 1.48 percent in 1977.
- The Beltwide average annual yield loss for the 47-year-period is 2.85 percent.
- There were 21 years with Beltwide yield losses above the 47-year annual average.
- There were 26 years with Beltwide yield losses below the 47-year annual average.
- The largest three-year variation in Beltwide yield losses was from 3.64 percent in 1976 to 1.48 percent in 1977 to 3.3 percent in 1978.
- The most dramatic five-year increase in Beltwide yield losses was 2.07 percent in 1962 to 4.03 percent in 1966.
- In recent years, the four lower Mid-South states have consistently ranked among the top five for seedling disease losses.
- In 1992, Mississippi, Arkansas, Tennessee and Louisiana were second, third, fourth and fifth behind Texas in losses to the diseases. In 1993, Louisiana was second followed by Mississippi, Tennessee and Arkansas and so on. Rarely did the losses for those states drop below 50,000 bales per state and in some years they approached 100,000 bales.
In most years, Blasingame notes, the Cotton Disease Council estimates losses due to seedling diseases at 2.5 percent to 3.5 percent, costing the U.S. cotton industry more than $100 million.
Several fungi appear to contribute to seedling disease infections in cotton, according to plant pathologists. The four primary pathogens are Rhizoctonia solani, Pythium spp., Fusarium spp. and Thielaviopsis basicola. Pythium and Thielaviopsis are more common in cool (59 to 68 degrees F), wet weather, while Rhizoctonia and Fusarium are more common under warmer (65 to 90 degrees F) conditions.
The most obvious symptoms of these diseases are skips in the planting row caused by seed decay or seedling death. Growers may see withered seedlings that have collapsed and died, they say.
Diseased plants may exhibit dark, necrotic lesions with an “ulcer-like appearance” on the lower stem. This symptom is commonly referred to “soreshin.” Stems with lesions that completely girdle a steam exhibit a symptom known as wirestem, which causes plants to wilt, collapse and eventually die.
For more information about seedling diseases, contact your county Extension agent or state Extension plant pathologist.