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=(k ₁ k ₂ +k _d)P whereP is the amount of pheromone component in the dispenser well;t is time;k ₁ is the ratio of the amount dissolved in the dispenser wall to the amount in the dispenser well;k ₁ 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=k ₁ k ₂ P For all three components during the first three weeks,k ₁ decreased from ca. 0.25 to ca. 0.10 and was approximately constant thereafter. The decrease ofk ₁ with time may have been caused by weather-induced cross-linking of the polyethylene. Over timek ₂ was constant and was 1.27 ± 0.26 × 10^–3/hr for1, 1.96 ± 0.33 × 10su–3/hr for 2, and 0.31± 0.05 × 10^–3/hr for 3. Thek ₂ was zero for2 and3 and 6.96 × 10^–4 for1. After 150 days in an orchard in 1991, 95% of1 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 for1 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 of1 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 for1, 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 of1 is required for reliable mating disruption, then the number of dispensers required would be changed proportionately.