tailieunhanh - BIOLOGICAL AND BIOTECHNOLOGICAL CONTROL OF INSECT PESTS - CHAPTER 5

Côn trùng điều chỉnh sự phát triển Điều hòa sinh trưởng côn trùng (IGRS) thuốc trừ sâu mà bắt chước các hành động của kích thích tố sự tăng trưởng và phát triển của côn trùng gây hại. Những lợi thế của việc sử dụng IGRS thay vì thuốc trừ sâu cổ điển trong kiểm soát dịch hại bao gồm giảm độc tính của họ. môi trường và độ đặc hiệu của họ cho côn trùng. Hơn nữa, bởi vì IGRS nhiều hoạt động cụ thể về các loài gây hại mục tiêu như Lepidoptera, họ cho thấy độc tính tối thiểu cho ký sinh trùng. | CHAPTER 5 Insect Growth Regulators Nancy E. Beckage CONTENTS Overview Ecdysteroid Agonists Juvenile Hormone Agonists Azadirachtin References OVERVIEW Insect growth regulators IGRs are insecticides that mimic the action of hormones on the growth and development of insect pests. The advantages of using IGRs instead of classic insecticides in pest control include their reduced toxicity to the environment and their specificity for insects. Moreover because many IGRs act specifically on target pests such as Lepidoptera they show minimal toxicity for beneficial parasites and predators. Williams 1967 was the first to suggest that insect hormones might be utilized as insect-specific environmentally benign pesticides and Staal 1982 presented a review of these strategies. Mimics of ecdysteroids molting hormones and juvenile hormones are two classes of hormone-based pesticides that have been developed for commercial use in insect pest control. Azadirachtin extracted from neem seeds also appears to disrupt growth and molting in a large number of insect species. These three classes of compounds will be discussed in this review. Insect growth and development are regulated by a combination of hormones including juvenile hormone ecdysteroids and several neuropeptides including eclosion hormone and ecdysis triggering hormone see Nijhout 1994 Riddiford 1994 Horodyski 1996 Zitnan et al. 1996 . During early larval life the JH titer is maintained at a high level and growth is interrupted by periodic molts that follow the release of 20-hydroxyecdysone by the prothoracic glands. The production of ecdysteroids occurs in response to the release of prothoracicotropic hormone from neurosecretory cells localized in the brain and retrocerebral complex. Following the production of a new cuticle during molting eclosion hormone is released followed by release of ecdysis-triggering hormone and the insect sheds the exuvium. In Lepidoptera the JH titer descends to nondetectable .