Fine-tuning Pesticide Applications on Cotton

By Jesús García
August 30, 2000

Cotton producers spend $75 million annually to control the tarnished plant bug. This year, Agricultural Research Service scientists will test the effectiveness of combining remotely-sensed, multispectral images with pest-scouting data to develop variable insecticide prescriptions that may do a better job of controlling this pest.

ARS entomologist Jeffrey Willers at the Crop Science Research Laboratory at Mississippi State, Miss., along with colleagues at the Stennis Space Center, Mississippi State University and Louisiana State University, will be building on research conducted in 1999. This research indicated that scouting and multispectral imagery data can be combined to create a geo-referenced pest density map. Such a map could then be uploaded into a pesticide ground sprayer that would dispense pesticide only where needed.

Cotton producers have traditionally had to depend on labor-intensive and time- consuming methods to determine levels of infestation--like searching for pests in randomly selected small sections of large fields. This often results in inaccurate pest counts and the spraying of entire fields, without regard to variations in pest density.

The new system uses multispectral imagery to draw a correlation between plant vigor and pest density. It relies on a digital camera sensitive to different wavelengths of light mounted in an aircraft flying over a cotton field at various altitudes. The camera records images that can then be processed to display variations in plant vigor. Next, scouts use transect-line search patterns and drop cloths to search for plant bugs in each of the areas corresponding to the different stages of growth captured by a digital image. ARS researchers have found that plant bugs are more common in areas with more vigorous plants.

This system is not only better at locating a variety of pests, but also provides growers with a more cost-effective method of controlling them by improving the placement and timing of pesticide applications. Rather than spray an entire field at one rate, this system allows growers to vary the coverage. Unsprayed areas can act as safe havens for a variety of beneficial insects that can then repopulate the field after spraying. This all translates into less chemical usage.

ARS is the chief research agency of the U.S. Department of Agriculture.

Scientific contact: Jeffrey L. Willers, ARS Crop Science Research Laboratory, Mississippi State, Miss.; phone (662) 320-7383, fax (662) 320-7528, jwillers@ra.msstate.edu.