Concern about the deleterious effects associated with synthetic chemicals has revived interest to explore plants as a source of natural insecticides for mosquito control. Ethnobotanical studies conducted in Kenya on plant species including bush mint, Hyptis suaveolens Poit., showed that many of them repel mosquitoes effectively when burned overnight in rooms. Recent field works conducted with H. suaveolens essential oil have demonstrated the potential of this essential oil as mosquito repellent. The present work is a comparative study on the persistence of 30% DEET and 10% H. suaveolens essential oil for personal protection against mosquitoes in field conditions. Twenty volunteers who have given their informed consent have been involved for each of the products and control (no treatment). Results showed that the mean number of mosquitoes that landed on treated volunteers 6 hours post-application was 0.50 and 0.45 for 10% H. suaveolens essential oil and DEET respectively, against 6 mosquitoes for the control people. Statistical analysis revealed that there is no significant difference between 10% H. suaveolens essential oil and DEET indicating that both products are similarly effective. The possibility to use H. suaveolens essential oil as integrated malaria vector management has been discussed.

Background The intensive use of chemical insecticides against mosquitoes has led to the development of widespread insecticide resistance. Control of Anopheles mosquitoes in malaria endemic areas of sub-Saharan Africa has become increasingly difficult. There is an urgent need for malaria control programmes to adopt more integrated mosquito management approaches that include sustainable, nonchemical solutions. The mermithid nematode Romanomermis iyengari is one of several natural control alternatives to synthetic pesticides for mosquito suppression. This study evaluated the effectiveness of the nematode R. iyengari for control of Anopheles gambiae . Methods The nematode R. iyengari was mass-produced, and pre-parasitic stage (J2) were used for laboratory and field experiments. In laboratory experiments, two concentrations of pre-parasitics (5 and 10 J2 per larva) were tested against first- (L1), second- (L2) and third-instar (L3) larvae of An. gambiae . Infected larvae were observed daily to determine their mortality rate and the number of post-parasitic nematodes emerging from dead larvae. In field experiments, 3500, 4000 and 5000 J2/m 2 were sprayed in separate natural Anopheles breeding sites. After treatment, the larval mosquito density in the breeding sites was assessed every 5–7 days. Results Laboratory results showed that larval An. gambiae is susceptible to nematode infection: 100% L1 larvae died within 24 hours post-treatment, and 100% of both L2 and L3 larvae died within 7 days, regardless of nematode concentrations. The average number of post-parasitic nematodes emerging per larva increased with increasing nematode concentration. In field experiments, the monthly applications of 3500 to 5000 pre-parasitic nematodes per m 2 eliminated larval mosquito development in Anopheles - and mixed breeding sites. Larval mosquito density dramatically decreased five days after the first treatment in all treated sites and was maintained at a very low level during the whole experimental period. Basically, only early instar larva were detected in treated sites throughout the test period. The average number of post-parasitic nematodes emerging per larva collected in treated sites was 1.45, 2, and 5.7 respectively for sites treated with 3500, 4000, and 5000 J2/m 2 . Conclusions Malaria mosquito larvae is susceptible to R. iyengari infection in West Africa. Parasitism intensity depends on tested nematode concentrations. Monthly application of 3500 J2/ m 2 was enough to control effectively larval An. gambiae in wetlands and f...

We studied the potential of the essential oil extract from the bush mint, Hyptis suaveolens, for use against mosquito biting under both laboratory and field conditions. In the laboratory, the repellency of various concentrations (1-6%) of the essential oil was assessed against Anopheles gambiae, based on a 15-min landing and biting on treated forearms of volunteers. In the laboratory, the percentage of mosquitoes landing on the forearm was 42, 33, 23, 23, 9, and 2 for 1%, 2%, 3%, 4%, 5%, and 6% essential oil concentration, respectively; and 92 and 91 for the solvent (isopropanol) and untreated control, respectively. The percentage of mosquitoes taking a blood meal was 22, 12, 13, 12, 5, and 3 for 1%, 2%, 3%, 4%, 5%, and 6% essential oil, respectively; and 52 and 51 for the solvent and control, respectively. In the field, the 6% essential oil repelled all mosquitoes immediately postapplication; this activity declined to 75% after 5 h. The repellent action of the 8% essential oil concentration was higher, 97% after 5 h. Based on these data, the essential oil of H. suaveolens appears to be a good candidate for use in the integrated management of mosquito vectors of disease.

Kaolin-based particle film has been developed in the United States for use in agriculture as crop protectant. This work is aimed to determine the optimal kaolin concentration for use against Aphis gossypii, the most damaging sucking insect of cotton in Benin, West Africa. Following kaolin concentrations have been tested in four different experiments: 2%, 3%, 4%, 5%, 6% and 8%. The effect of kaolin is tested by recording the population dynamics of A. gossypii on cotton after spraying. Results showed that the solution containing 5% of kaolin has significantly reduced aphids' number. This concentration corresponds to a maximum of 18 kg of kaolin per hectare for the entire season when ultra low volume sprayer is used. Higher kaolin concentrations have left a large deposit of kaolin particle on cotton leaves thus handicapping chlorophyll synthesis and the proper growth and development of the plants. To obtain encouraging results, an adequate application method that provides a full and continuous coverage of the plants with kaolin particle film should be used. We suggest conducting trials on this product in practical cotton production conditions in West Africa to assess its potentiality as integrated pest management (IPM) component.

Abstract:Infestations of the aphid Lipaphis erysimi Kalt.cause a mean yield loss of cabbage that varies from 35.4% to 73.3% depending from agro-climatic conditions. To control this pest insect in Sub-saharan Africa, synthetic chemical insecticides are usually applied. Kaolin is a white, non-abrasive, inert aluminosilicate mineral that has been shown to effectively protect host plants from insect pests including lepidopterans, sucking insects and mites. The present work is aimed to study the effects of kaolin on the population dynamics of L. erysimi for the Integrated Management of this insect pest in cabbage. To carry out the present study, kaolin powder was dissolved in water to obtain a concentration of 5% kaolin. The plants were sprayed with kaolin suspension every week and every 4-days in 2 respective experiments. Results showed that kaolin sprays significantly reduced aphid populations density. Nevertheless, more frequent applications (every 4 days) did not improve kaolin efficacy. It is concluded that kaolin technology should be combined with another plant protection measure in order to keep aphids population under control in cabbage.