Location: Mosquito and Fly Research Unit
Title: Combined effect of seaweed Sargassum wightii Greville extract and Bacillus thuringiensis var. israelensis against the malaria vector, Anopheles sundaicus (L). Authors
|Prasanna Kumar, Kanagarajan -|
|Murugan, Kadarkarai -|
|Kovendan, Kalimuthu -|
|Naresh Kumar, Arjunan -|
|Hwang, Jiang-Shiou -|
Submitted to: Science Asia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 18, 2011
Publication Date: N/A
Interpretive Summary: An important threat to effective control of disease-transmitting mosquitoes is resistance to synthetic chemical insecticides in the mosquito population. Long term use of synthetic chemicals for vector control can also disrupt natural biocontrol systems. Botanical insecticides are an alternative to synthetic insecticides and are relatively safe and biodegradable and often can be obtained from local sources. In this study, Bharathiar University (India) and ARS scientists evaluated extracts from seaweed for toxicity to the immature stages of a malaria vector in India. The extract caused significant mortality in mosquitoes in laboratory and field tests and the toxicity of the extract to immature mosquitoes was increased by up to 200% when combined with a bacterium known as Bti. The results of the study suggest that seaweed phytochemicals alone and in combination with pathogenic bacteria may provide effective control of malaria vectors.
Technical Abstract: Studies were made of the extract of Sargassum wightii combined with Bacillus thuringiensis var. israelensis (Bti) for control of the malaria vector Anopheles sundaicus. Treatment of mosquito larvae with 0.001% S. wightii extract indicated median lethal concentrations (LC50) of 88, 73, 134, 156, and 171 ppm for 1st through 4th instars and pupae, respectively. The LC90s for 1st through 4th instars were 273, 243, 303, and 321 ppm, and for pupae, 323 ppm. Using 0.01% S. wightii extract as a mosquito repellent on skin resulted in 89% protection from bites by female An sundaicus after 2 h. Sargassum wightii extract combined with Bti lengthened larval development and adult emergence times and synergy from the combination of both agents increased larval and pupal mortality rates by 1.7 x, 1.9 x, 1.4 x, 1.3 x and 1.2 x for instars 1- 4 and pupae, respectively. The result show that seaweed extract combined with the application of Bti induced significant mortality and growth inhibitory effects in immature mosquitoes.