Behavior of codling moth (Lepidoptera: Tortricidae)neonate larvae on surfaces treated with microencapsulated pear ester

Authors: Light, Douglas; Beck, John

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2012
Publication Date: 6/1/2012
Citation: Light, D.M., Beck, J.J. 2012. Behavior of codling moth (Lepidoptera: Tortricidae)neonate larvae on surfaces treated with microencapsulated pear ester. Environmental Entomology. 41(3):603-611.

Interpretive Summary: Codling moth (CM), Cydia pomonella, larvae cause severe damage to apples, pears and walnuts worldwide by feeding and introducing molds and spoilage micro-organisms. CM larvae are attracted to and stop their crawling by a pear fruit odor compound named the “pear ester” (PE). When added to insecticide sprays, a microencapsulated form of PE (PE-MEC) has enhanced the effectiveness of insecticides against CM. PE-MEC is comprised of numerous, small microcapsules that emit very small amounts of PE for an estimated 2.5 – 3 weeks. Reported here are the laboratory behavioral activities of newly-hatched neonate CM larvae to sprayings on either filter paper or apple-leaf surfaces of PE-MEC compared to a “control” treatment of just water-alone. PE-MEC was sprayed at a dilute, 1/32,000 dose, equivalent to the specified field spray application rate. When applied to half of the filter paper, the PE-MEC treatment caused strong attraction and dramatically longer time spent on the PE-MEC treated surfaces than the water-alone treated surfaces. The attraction to and prolonged crawling - occupation time within the PE-MEC treated areas were observed in repeated experiments for up to 14 days of aging of the filter papers. When applied to apple leaves, PE-MEC caused dramatic changes in neonate orientation preferences over the water-alone control, causing more frequent and longer time periods of stopping or “arrestment.” PE-MEC also affected neonates’ ability to find their way up to the leaf base and onto the stem. PE-MEC caused larvae to take a much longer time to crawl 2/3 the distance up the leaf and only 10% of the released larvae found the leaf base, while over 80% were successful on the water –alone treated leaves. Effects of PE-MEC on extended crawling time, turning, and stopping - arrestment by CM larvae, suggests that PE-MEC promotes “larval wandering” and greater exposure in time – space of neonates on leaves, and this could disrupt fruit/nut finding and enhance mortality by increasing the exposure to sprayed insecticides.

Technical Abstract: Codling moth (CM), Cydia pomonella, larvae cause severe damage apples, pears and walnuts worldwide by internal feeding and the introduction of molds and spoilage micro-organisms. CM neonate larvae are attracted to and arrested by a pear-derived kairomone, ethyl (2E,4Z)-2,4-decadienoate, the “pear ester” (PE). As a spray additive, microencapsulated formulation of PE (PE-MEC) has enhanced the efficacy of insecticides against CM. PE-MEC formulation allows for picogram/hr emission of PE for an estimated 2.5 – 3 weeks. Reported here are the laboratory behavioral activities of neonate CM larvae to applications on either filter paper or apple-leaf surfaces of treatments of PE-MEC compared to a water-alone control. PE-MEC was applied at a dilute, 1/32,000 dose, equivalent to the specified field spray application rate. When applied in a dual-choice test to half zones of filter paper, the PE-MEC treatment elicited strong attraction and significantly longer time spent on treated surfaces than controls. The effects of attraction and prolonged occupation time were observed in repeated experiments for up to 14 days of aging and evaporative loss of PE from the filter papers. When applied to entire apple leaves, PE-MEC caused significant changes in neonate orientation preferences over the water-alone control, eliciting more frequent and significantly longer time periods of stopping or arrestment. PE-MEC also affected neonates’ ability to find their way up to the leaf base and onto the stem – petiole. PE-MEC elicited significantly longer time for larvae to progress 2/3 the distance up the leaf and only 10% of the released larvae found the leaf base, while over 80% were successful on the water –alone treated leaves. Effects of PE-MEC on extended crawling time, turning, and arrestment by CM larvae, suggests that it promotes “larval wandering” and greater temporal – spatial exposure of neonates on leaves that could disrupt fruit/nut finding and enhance mortality by increasing the exposure to insecticides.