Linda Benedict, Blanchard, Tobie M. | 5/16/2012 7:19:09 PM
Few crops have the storied history of cotton. Grown in Louisiana for hundreds of years, this crop has been a vital part of the state’s economy. In the early 1700s, cotton cultivated in the state was used mainly for home spinning and weaving. It wasn’t until the invention of the cotton gin later that century that cotton became a cash crop in Louisiana.
For more than 100 years cotton has been the most important crop grown in northeast Louisiana. Crucial to the continued success of the state’s cotton industry has been the research conducted by the Louisiana Agricultural Experiment Station. This research has been instrumental in increasing yields, reducing production costs and minimizing losses from insect pests, weeds, nematodes and plant diseases. Much of the initial research in cotton was done on the Calhoun Research Station in Ouachita Parish.
For many years cotton was one of the most management-intensive and expensive field crops to grow in Louisiana. A big factor in the cost of production is controlling insect pests. Until recently, the key pest in cotton was the boll weevil, which plagued farmers in the state since the early 1900s, causing them to rely heavily on pesticides, which created other pest issues and environmental problems.
In the mid-1950s, entomologists John Roussel, Dan Clower and a graduate student, Ray Young, discovered boll weevil resistance to the insecticide DDT. This research documented the first large-scale problem of pesticide resistance shown in a major U.S. crop pest.
Working in the 1950s, 1960s and 1970s, entomologists L.D. Newsom and James R. Brazzel focused their research efforts on the biology of the boll weevil, establishing principles of insect hibernation or diapause, a state of resting during the winter months when no cotton was available. The knowledge of diapause coupled with the fact that cotton was the only reproductive host for this pest were exploited as critical to U.S. boll weevil eradication.
LSU AgCenter scientists served as the technical advisers to the Louisiana Department of Agriculture and Forestry’s Boll Weevil Eradication Commission, which began working to eliminate the pest in the 1990s. The researchers worked out technical procedures such as what chemicals to use and trapping protocols. The boll weevil was considered officially eradicated in 2011.
“It was a huge project involving every cotton producer in the state and required many years to complete,” said John Barnett, LSU AgCenter Northeast Region Director and former cotton specialist.
The overall result of this success was a tremendous reduction in the frequency of insecticide applications on cotton.
In the 1960s and 1970s, Newsom and Jack Jones helped identify plant resistance to a common problem in Louisiana, the root-knot nematode, which attacks the roots of cotton plants.
Newsom also was credited with helping develop early integrated pest management systems in cotton, which moderated pesticide use. Elements of the integrated pest management system included research focused on the population ecology of pest species, breeding for resistant crop varieties, adjusting planting and harvest dates, managing overwintering populations, destruction of crop residue, limited use of selective insecticides at the most effective times, and attracting small overwintered populations with pheromones.
In the early 1990s, transgenic technologies were introduced into cotton plants. Genes from a naturally occurring soil bacterium, Bacillus thuringiensis, which is toxic to certain insects including the tobacco budworm and the boll worm, were inserted into cotton plants. This cotton is known as Bt cotton.
“This technology was truly a revolutionary development in the history of pest control in agronomic crops,” said Larry Rogers, former director of the Louisiana Agricultural Experiment Station, now retired.
Rogers, who also served as the resident director of the Northeast Research Station, said entomologists at that station were regarded as some of the best cotton entomologists in the world.
"As a result of their expertise and their commitment, the Northeast Research Station with expertise in entomology and agronomy was selected as one of the few sites in the United States where the effectiveness of transgenic Bt cotton lines was field-tested,” Rogers said.
Because of the success of this technology, the Louisiana cotton industry further reduced the need for synthetic pesticides to control caterpillar pests. With Louisiana’s subtropical climate and the diversity of cotton insect pests, however, cotton production still requires the use of pesticides to maintain optimum crop productivity.
LSU AgCenter entomologists Rogers Leonard and Ralph Bagwell, along with a team of engineers, computer scientists and members of the cotton industry, have advanced integrated pest management strategies by studying prescription pesticide applications that limit sprays only to those areas of a field which actually need the pesticide.
The first demonstration of an aerially-applied prescription treatment in the United States was done in Tensas Parish on cotton in 2002. Other scientists have used similar techniques to study and implement technologies that apply crop inputs to restricted field zones only when needed. Agronomists and nematologists have developed soil-sampling protocols and application technologies to more efficiently apply products.
Some of the first trials in Louisiana were designed to evaluate the adaptation and performance of cotton varieties. Original research reports from the first experiment stations in New Orleans, Baton Rouge and Calhoun during the late 1800s provided information to the cotton industry on which varieties were the best fit for their conditions. Those evaluations continue today for cotton at AgCenter research stations.
“This is the sole source of unbiased data that producers have,” said John Kruse, AgCenter cotton specialist. “When it comes to which varieties to grow, this information is vital to their decision-making process.”
LSU AgCenter agronomists had successes dating back to the 1920s when cotton breeding began in earnest in Louisiana with H.B. Brown. Early studies by Brown involved leaf shape and plant development, trying to increase yield and reduce the impact of insects and diseases.
Jones conducted cotton breeding work from the 1950s to 1990s. Jones’ research focused on the plant disease Fusarium wilt, nematodes, key insect pests and plant canopy characteristics.
Late-season diseases that rot the bolls before the crop could be harvested were a major problem in south Louisiana. In the 1970s and 1980s, Jones released three varieties with unique narrow leaf shapes – Gumbo, Pronto and Gumbo 500.
“They were released to control boll rot,” Jones said. “These leaf shapes were similar to okra leaves and would open up the canopy and let the cotton dry out after rainfall events.”
Another significant cotton line released during Jones’ tenure was Louisiana 887, which had resistance to root-knot nematode and Fusarium wilt.
“We had some resistant varieties, but they were always sacrificing some yield. But this one was just as good at yielding on noninfested soil as it was on infested soil,” Jones said.
Even though it was released in 1990, this line would go on to be crossed with other popular varieties released over the past two decades, including transgenic varieties that have the Bollgard gene for insect resistance and the Roundup Ready gene for herbicide resistance.
Agronomic Practices, Weed Management, Conservation Tillage
To maximize cotton yields each year, additional nutrients in the form of fertilizers must be applied. Some of the first work with a unique nitrogen source, anhydrous ammonia, was done with LSU AgCenter engineers developing application equipment. The use of winter cover crops to provide a natural source of organic matter and nitrogen for cotton production was studied for many years at the Dean Lee, Red River and Baton Rouge sites.
Many of these studies were continued for more than 25 years, and this work was initially responsible for paving the path for the future of conservation tillage systems and alternative sources of soil amendments for fertility.
Robert Hutchinson initiated long-term field studies at the Macon Ridge Research Station in 1987 to evaluate the effects of tillage practices on cotton production and soil erosion. The original work was done on highly erodible soils but has continued to evolve into production systems for all soils across the state.
Conservation tillage systems for cotton produce yields similar to or higher than cotton planted in surface-tillage treatments. Adoption of conservation tillage practices can enhance soil productivity, decrease input costs and reduce contamination of surface water resources by sediment, fertilizer nutrients and pesticides.
“Conservation tillage minimized the use of equipment, made farming more efficient while improving organic matter and the capacity to control erosion,” Barnett said. “It’s been economically and environmentally beneficial to Louisiana agriculture.”
Weed control options were limited tillage and hand-weeding prior to the 1950s. LSU AgCenter agricultural engineers experimented for manyyears with flame cultivation as a tool for weed management after cotton emerged. With the discovery of synthetic herbicides, LSU AgCenter weed scientists have had a rich history with developing herbicide use programs in cotton ranging from the use of soil-incorporated products such as Treflan to the newest transgenic herbicide-tolerant cotton lines.
Conservation tillage practices have become even more successful with the development of herbicide-tolerant cotton plants. These technologies have allowed growers to use herbicides as sprays over their cotton crop to control weeds for the entire season without any crop injury.
Cotton Tradition Continues
Cotton acreage in Louisiana has dwindled in the past 10 years with lows falling below a quarter of a million acres. Farmers have switched to planting more corn as markets shifted and corn varieties improved.
This practice of shifting crops has long-term overall farm productivity effects as well. Original research during the first years after forming the Louisiana Agricultural Experiment Stations focused on crop production by rotating annual crops. These research results collected 125 years ago support the actions of farmers today. Rotating cotton with other adapted crops continues to produce the most sustainable income stream in many Louisiana regions.
Despite the changes, Louisiana’s cotton industry remains stable. “I don’t see the return to king cotton days we had for many years, but Louisiana farmers will remain substantial producers of cotton,” Barnett said.
The crop retains its proud legacy as farmers who grow more soybeans or corn still see themselves as cotton farmers and uphold the tradition of cotton as an important part of the state’s fabric.
Tobie Blanchard, LSU AgCenter Associate Communications Specialist, Baton Rouge, La.
(A shorter version of this article appeared in the spring 2012 issue of Louisiana Agriculture magazine.)