PERFORMANCE-CHARACTERISTICS OF A COMMERCIAL CONTROLLED-RELEASE DISPENSER OF SEX-PHEROMONE FOR CONTROL OF CODLING MOTH (CYDIA-POMONELLA) BY MATING DISRUPTION

Performance characteristics of polyethylene tube dispensers containing a mixture of (E,E)-8,10-dodecadien-1-ol (1), dodecan-1-ol (2), and tetradecan-1-ol (3) were evaluated for suitability as a mating disruptant for codling moth control. The rate of loss of pheromone component from a dispenser at any time was found to be described by the equation: -dP/dt = (k1k2 + k(d))P where P is the amount of pheromone component in the dispenser well; t is time; k1 is the ratio of the amount dissolved in the dispenser wall to the amount in the dispenser well; k2 is the ratio of the evaporation rate to the amount dissolved in the dispenser wall; k(d) is the rate constant for chemical decomposition. The evaporation rate, E, of a pheromone component at any time was given by: E = k1k2P For all three components during the first three weeks, k1 decreased from ca. 0.25 to ca. 0. 10 and was approximately constant thereafter. The decrease of k1 with time may have been caused by weather-induced cross-linking of the polyethylene. Over time k2 was constant and was 1.27 +/- 0.26 x 10(-3)/hr for 1, 1.96 +/- 0.33 x 10(-3)/hr for 2, and 0.31 +/- 0.05 x 10(-3)/hr for 3. The k(d) was zero for 2 and 3 and 6.96 x 10(-4) for 1. After 150 days in an orchard in 1991, 95 % of 1 was lost from the dispensers (61 % of the loss was by chemical decomposition and 39% by evaporation). The heat summation units in a Yakima valley orchard during 1991 were 4.7% above the average for the 1980-1991 period, while during 1990 they were the highest for this period (26% above average). After the first three weeks of dispenser aging, the regression line half-lives for 1 for 1990 and 1991 were 31.0 and 35.1 days, respectively. The difference in temperature between 1990 and 1991 did not affect the half-life of 1 very much because so much of the loss was from photochemically induced decomposition. Based on an estimate of the required minimum evaporation rate for mating disruption of 2 mg/ha-hr and a half-life of 35 days for 1, 2345 dispensers/ha would be required for one application per season; 944 dispensers/ha for two applications per season; and 734 dispensers/ ha for three applications per season. If a different emission rate of 1 is required for reliable mating disruption, then the number of dispensers required would be changed proportionately.