Effectiveness of Bacillus thuringiensis and Bacillus sphaericus isolates against Culex pipiens, Aedes aegypti and Anopheles sergenti mosquito larvae

Mosquito borne diseases are continuing to be major health problems for exposed populations. Biological control alone or as a part of integrated vector management is believed to be a better alternative to the chemical control aimed against pest mosquitoes. The present study is designed to screen the larvicidal effect of Bacillus thuringiensis [Bf] and Bacillus sphaericus [Bs] against larvae of three species of mosquitoes larvae namely, Culex pipiens, Aedes aegypti and Anopheles sergenti. Mosquito Larvae were collected from different water resources and identified by standard procedures. Fourth-instar larvae were used in the bioassays. From the 50 samples of mud [15], soil [15] and water [20], 125 microbial isolates were purified and screened for larvicidal activity. The pure solubilized protein from Bs/Bt was quantified for protein estimation. For every 100 ml of the test solution 10 larvae were added in a 250 ml flask. Concentrations that killed 50% [LC[50]] and 90% [LC[90]] of the exposed mosquito larvae were determined. From a total of 125 bacterial isolates, only 25 isolates of Bt [13] and Bs [12] were found to have mosquito larvicidal effect. The highest larval mortality occurred with four isolates of Bt [Bt1, Bt2, Bt3, Bt4] and one Bs [Bs1] isolate. Their mortality rate [LC[50]] values were 0.0151, 0.0160, 0.0217, 0.0252 and 0.0330 mgI1, respectively. The [LC[90]] values of the five Bacillus isolates [Bt/Bs] were 0.0218,0.0219,0.0225,0.0341 and 0.0367, respectively. Time taken for larvicidal activity of the four Bt isolates showed LT[50] at 6,12,12 and 18 h and LT[100] at 24, 30, 36 and 48 h respectively. Bs showed LT[50] at 24 h and LT[100] at 48 h. This study confirms the utilization of larvicidal bacteria as Bt/Bs as commercial mosquito larvicidal and biological controlling agents

study on biological control of six fresh water snails of medical and veterinary importance

This study evaluated the molluscicidal effect of Commiphora molmol oil extract [Myrrh], on control of six fresh water snails [Lymnaea natalensis, Bilinus truncatus, Biomphalaria alexandrina, Physa acuta, Melania tuberculata and Cleopatra bulimoides]. Also, the extract effect on the egg masses of L. natalensis, B. truncatus, B. alexandrina and Ph. acuta was evaluated. Snails and egg masses were exposed at 16-20°C to various concentrations [conc.]- LD[50] after 24 hours exposure were 264/132, 283/195, 230/252, 200/224, 241/246 and 241/246 ppm for young/adult of L natalensis, B. truncatus, B. alexandrina, Ph. acuta, M. tuberculata and C. bulimoides respectively. LD[100] after 24 hours exposure were 400/400 for L. natalensis, B. truncatus, B. alexandrina, M. tuberculata and C. bulimoides, and 300/300 for Ph. acuta. Also, complete mortality [100%] was achieved for the egg masses of L. natalensis, B. truncatus, B. alexandrina and Ph. acuta at concentrations of 300, 200, 300 and 400 ppm respectively. Lower concentrations gave the same results after longer exposure. LD[100] of C. molmol oil extract [Myrrh] had a rapid lethal effect on the six snail species and their egg masses in high conc, of 300 and 400 ppm. Commiphora molmol is a promising plant to be included with the candidate plant molluscicides. The oil extract of this plant showed a remarkable molluscicidal activity against used snail species

Helobdella nilae and Alboglossiphonia conjugata leeches as biological agents for snails control

The efficacy of leeches, as biological agents, in control of snail intermediate hosts of schistosomiasis [Bulinus truncatus, Biomphalaria alexandrina] and fascioliasis [Lymnaea natalensis] as well as their effect on the non-target snails Physa acuta, Melanioides tuberculata and Cleopatra bulimoides was evaluated. Two glossiphoniid snail leeches, Helobdella nilae and Alboglossiphonia conjugata were used. They destroyed egg masses and young snails more rapidly than adult ones. H. nilae showed a stronger destructive effect than A. conjugata. In a descending order, it preferred L. natalensis followed by B. truncatus, B. alexandrina, Ph. acuta, M. tuberculata and lastly C. bulimoides. But, A. conjugata preferred L. natalensis followed by B. truncatus, Ph. acuta, M. tuberculata, B. alexandrina and lastly C. bulimoides. The detailed diagnostic morphology and biology of the two leeches were given