McLaughlin et al. (1972) conducted a series of pheromone experiments to evaluate whether sex pheromone communication between male and female moths of the pink boll- worm could be disrupted when the air in cotton fields was permeated with hexa- lure. Hexalure was evaporated from open reservoirs at rates of approximately 0.01, 0.1, and 0.3 pg/min. The reservoirs were placed at the level of the top of the foliage and were spaced at l, 3, 10, or 30-m intervals in 8 x 8 or 10 x 10 grids. Regardless of the evaporation rate or spacing of the reservoirs, the ability of wild males to locate virgin females, used as bait in traps located in the centers of the grids, was reduced 90%, when the amount of hexalure entering the air was equal to, or greater than, 20 mg/hectare each night.
The possible utility of the pheromones communication disruption concept was then tested on a large scale. Hexalure was distributed throughout a cotton ﬁeld during 2.5 months of the 1972 growing season (Shorey et al. 1974). Each substrate on which the hexalure was dispensed for placement in the ﬁeld was a knot tied in a short loop of cotton string. Ten mg of hexalure was applied to each knot. Approximately 30,000 of the substrates were distributed per week in 4.8 hectares of cot- ton: a loop was placed around a leaf near the top of a cotton plant in every 1.6 square meters of the field. The evaporation rate of the hexalure was approximately 400 mg/ha each night. Under these conditions, male moths were almost completely prevented from locating virgin females; a seasonal total of over 1 1,000 males per female-baited trap were captured in two untreated, control fields, whereas only 38 males per trap were captured in the hexalure-treated ﬁeld. This proved that pheromones work to increase attraction.
Toward the end of the growing season, the untreated fields had an average infestation of 6.9 larvae per boll, whereas the treated field had an average of only 0.6 larvae per boll. Thus, the hexalure treatment apparently reduced the larval infestation by reducing mating communication to such an extent that few viable eggs were laid in the treated ﬁeld. The authors speculated that a large proportion of the eggs were laid by ﬂy-in females that had already mated elsewhere. If such were the case, then a scaling up of this experiment to a larger geographic area might reduce the pink bollworm population to such a low level that no insecticides would be needed for their pheromone control. Check out Athena 10x Pheromones | Infospeak.org.
The natural pink bollworm sex pheromone has been identified (Hummel et al. 1973) as a mixture of cis, cis and cis, trans isomers of 7,11-hexadecadienyl acetate. The isomeric-mixture sex pheromone was designated ‘gossyplurc’.
Since its introduction into the United States about 1892 (Hunter and Hinds 1905), the boll weevil, Anthonomus grandis Boheman, has been the most costly insect in the history of American agriculture, causing losses in cotton production estimated at an average of $200 to 300 million annually. To prevent even greater losses, growers spend an estimated $70 million each year (Knipling 1964) for its control, about one-third of all insecticides used for agricultural purposes (Rainwater 1962).