Suwannee Promsiri. Screening medicinal plant extracts for larvicidal properties and other effects on Aedes Aegypti (Diptera : Culicidae) and toxicity to a non-target organism. Doctoral Degree(Biology). Mahidol University. : Mahidol University, 2009-04-01.
Screening medicinal plant extracts for larvicidal properties and other effects on Aedes Aegypti (Diptera : Culicidae) and toxicity to a non-target organism
การคัดเลือกสมุนไพรเพื่อเป็นยาฆ่าลูกน้ำและศึกษาผลกระทบต่อวงจรชีวิต รูปร่างลักษณะทางสัณฐานวิทยาและตำแหน่งที่ทำให้ยุงลายชนิด Aedes aegypti ตาย
Abstract:
The present study is composed of three parts. The first part was a screening of medicinal plant extracts for larvicidal properties on Aedes aegypti and toxicity to nontarget organisms. A preliminary study was conducted on Ae. aegypti for the effects of extracts of one hundred and twelve medicinal plant species collected from the southern part of Thailand. Studies of the larvicidal properties of extracts against the third and fourth instar larvae of Ae. aegypti determined fourteen species to have high toxicity. Mammea siamensis Kost., Anethum graveolens L. and Annona muricata L. were the three species of common and inexpensive herbs selected for further study. The extracts were the most effective against the third and fourth instar larvae at very low concentrations, their LC50 and LC90 values being 4.1 and 14.0 mg/l for M. siamensis, 13.7 and 48.8 mg/l for A. graveolens and 53.9 and 192.3 mg/l for A. muricata, respectively. They had no or very low toxicity to guppy fish. The extracts had a second effect: to effect larval development and life cycle of Ae. aegypti. The results showed that they affected the reproductive potential of surviving adult mosquitoes by reducing the number of eggs laid and egg hatchability. All instar larvae were very susceptible to these three extracts. The first instar larvae were very susceptible to A. muricata, the second to A. graveolens, while the third and fourth instars were susceptible to M. siamensis. These extracts delayed larval development and inhibited adult emergence. There were no adverse effects on non-target organisms at LC50 and LC90 values, except for M. siamensis at its LC50. The extracts had a third effect: to produce morphological aberration and cause possible damage to the larvae and pupae. When the first, second, third and fourth instar larvae of Ae. aegypti were exposed to the LC50 values of three extracts, the majority of the treated population died with normal larvae. The forms of morphological berration varied with the stages and the species of medicinal plants. These medicinal plant extracts mostly damaged anal gill, integument, siphon apex and terminal segments, and in the pupal stages the eighth segment, paddles, hypopygium and cephalothorax. The possible sites of action of the three extracts on fourth instar larvae were confirmed by diagnostic scanning electron microscopy. It was found that most organs were damaged, especially the anal gills and cuticular sculpturing.