|Mayer, M. - RETIRED USDA, ARS, CMAVE|
Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 25, 2001
Publication Date: N/A
Interpretive Summary: The beet armyworm is a major pest of many crops throughout the U.S. and around the world. To protect crops, growers typically resort to making multiple applications of chemical pesticides. Mating disruption offers and alternative to conventional pesticides, and this technology has been demonstrated effective for control of beet armyworm. However, the current technology is very expensive because of the quantity of pheromone required and the cost of application. Scientists at the Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL, are investigating ways of improving the cost effectiveness of mating disruption for managing beet armyworm in cotton and vegetable crops. Shin-Etsu Yoto-con-S 'rope' pheromone dispensers loaded with an off blend of two pheromone components were applied in cotton at different site densities totaling 112 g ai/ha. As few as 25 sites/ha effectively reduced mating by females by 94% for >10 weeks. These results compared favorably to an earlier large-scale field experiment in which beet armyworm larval populations were reduced 95% using 500 pheromone-dispensing sites/ha and 160 g total pheromone/ha. Airborne measurements of the pheromone laden atmosphere over the treated plots showed that the amount in the air was 140 times less than expected from a single calling female. The results provide a benchmark for effective pheromone application levels in terms of quantity of pheromone required, usable pheromone blend and the number of treatment sites needed effect control of mating. These improvements provide substantial saving in material and applications costs making this technology cost competitive with conventional control methods.
Technical Abstract: Field experiments were conducted to evaluate Shin-Etsu Yoto-con-S**R 'rope' pheromone dispensers applied in cotton to determine efficacy in disrupting sexual communication and mating of beet armyworm moths, Spodoptera exigua (Hubner), and obtain atmospheric measurements of the disruptant pheromone components in and away from treated areas. The number of pheromone dispensing sites/ha ranged from 25 with 20 ropes/site to of 247 sites with 2 ropes each. A total of 112 g pheromone of a 70:30 blend of (Z,E)-9,12- tetradecadien-1-ol acetate (ZETA) and (Z)-tetradecen-1-ol (Z9-14:OH) was applied/ha. As few as 25 sites/ha effectively disrupted sexual communication to traps by 91% and mating by females by 94% for at least 10 weeks. The results compared favorably to an earlier large-scale field experiment in which beet armyworm larval populations were reduced 95% using 500 pheromone dispensing sites/ha (2 ropes/site) and 160 g total pheromone/ha. The airborne concentration of ZETA and Z9-14:OH measured within the pheromone plots was 1.5 X 10**-13 M and 1.2 X 10**-13 M, respectively. The airborne concentration of ZETA and Z9-14:OH in the vicinity of a female was estimated to range between 2.1 X 10**-11 M and 2.4 X 10**-12 M, respectively. Thus, the average ZETA and Z9-14:OH concentration in the treated plots was about 140 and 20 times less, respectively, than that expected from a single female. Estimates of these parameters provide a benchmark for the requisite pheromone concentration in the atmosphere to achieve a high level of mating disruption for beet armyworm and possibly other insect pest species.