Influence of certain fertilizers on the activity of some molluscicide against Biomphalaria Alexandrina and lymnaea natalensis snails

Effect of the fertilizers [ammonium nitrate, potassium sul- phate and urea] on molluscicides [copper sulphate, niclosamide and mollutox] against B. alexand-rina and L. natalensis was investigated. The molluscicides were more potant than fertilizers. Snails were exposed for 24 hr to a fertilizers using LC0 [1/10 and LC50] than, to molluscicides. Per- exposure to potassium sulphate caused a synergistic action with copper sulphate, niclosamide and mollutox on L. natalen-sis. Pre-exposure to urea caused an additive effect with niclo-samide and mollutox against L. natalensis and B. alexandrina res- pectively. Pre-exposure to ammonium nitrate caused an additive action to niclosamide on L. natalensis. Snails exposed for 24hr to one molluscicide, then exposed to fertilizers, showed that pre-exposure to niclosamide or mollutox caused an additive effect with ammonium nitrate and potassium sulphate. Pre-expo-sure to mollutox caused an additive effect with urea on the two snails' sp. Juvenile or adult B. alexandrina were ex-posed to LC0 of molluscicde-fertilizer mixture, showed that urea when mixed with each molluscicides showed greatly reduced on the growth rate percent, survival rate and snail fecundity mollus-cicides and fertilizers mixed at ratios of LC [40:10,30:20, 25:25, 20:30 and 10:40], the toxicity of the mixtures cau-sed antagonistic effect on adult B. alexandrina, but a mixture of niclosamide-ammonium nitrate caused a potent effect [syner-gism or additive] except at ratio 20:30 which showed an antago-nism on L. natalensis. Mixtures of copper sulphatepotassium sulphate [10:40], niclosamide-potassium sulphate [20:30], moll-utox-ammonium nitrate [25:25] revealed an additive effect on L. natalensis.

Semifield trials to control biomphalaria Alexandrina by different modes of exposure to certain plant and chemical molluscicides

Semi-field trials were carried out in Snail Research Station under simulated natural conditions to evaluate different modes of exposure to Anagallis arvensis and Calendula micrantha as plant molluscicides and bayluscide and copper sulphate as chemical molluscicides. Firstly, B. alexandrina were exposed to the tested molluscicides alone and in addition to two densities of aquatic plants. No apparent effect of aquatic plants on the activity of both plant and chemical molluscicides, this may be due that the two densities of the aquatic plants used were insufficient to interfere with the molluscicides action. Secondly, snails were pre-exposed to three sub-lethal concentrations of the plant molluscicides for 24h then to three concentrations of the chemical molluscicides and vice versa. The results indicate that the pre-exposure increases the snail mortality significantly in all treatments of bayluscide and A. arvensis [except in the highest concentration when the snails firstly exposed to bayluscide then to A. arvensis, where the two compared treatment showed 100%] and in all treatments of bayluscide and C. micrantha. Also, in one treatment of copper sulphate and A. arvensis [in the highest concentration when the snails firstly exposed to A. arvensis then to copper sulphate] and in three treatments of copper sulphate and C. micrantha, [in least and moderate concentrations when snails firstly exposed to C. micrantha then to copper sulphate and in the highest concentration when snails firstly exposed to copper sulphate then to C. micrantha]. Thirdly, snails were exposed to mixtures of six different ratios of hayluscide and each of A. arvensiS and C. micrantha. The results indicated that the snail mortality increased significantly only in the first treatient of bayluscide and A. arvensis mixtures and in treatment number 6 of bayluscide and C. micrantha

molluscicidal efficacy of three products against Biomphalaria alexandrina and Lymnaea natalensis

The toxicity of three local formulated products [Sol EC [mineral oil], Sisi-6 [surfactant] and castor bean oil EC [plant oil]] was tested against Biomphalaria alexandrina and Lymnaea natalensis in two water sources. The results indicated that in dechlorinated water after 24-hour exposure, castor bean oil was the most toxic product against the snails, followed by Sisi-6 and Sol [EC] with LC90 of 250 ppm and 8 ppm against B. alexandrina and L. natalensis, respectively. When Nile water was used after 6-hour exposure, a high concentration of castor bean oil [4 LC90] did not cause 100% mortality of the snails; it was achieved by 2 LC90 of Sisi-6 with Nile water. On the other hand, castor bean oil was more fatal to eggs of the snails [LC90 = 660 ppm] than the other two products. In general, L. natalensis was more susceptible to the experimental products than B. alexandrina