Screening for adulticidal bioactivity of South African plants against Anopheles arabiensis

381 crude extracts of 80 plant taxa in 42 families were sprayed onto ceramic tiles and screened using the cone bio-assay method for insecticide efficacy testing. Blood-fed, female Anopheles arabiensis mosquitoes were exposed to the treated tiles for a period of sixty minutes. Mosquito mortality was monitored for twenty-four hours.Of all the extracts analysed, the highest activity was observed in Ptaeroxylon obliquum (Ptaeroxylaceae) and Pittosporum viridiflorum (Pittosporaceae), a single extract from each, exhibiting more than 50% mortality. A large proportion (81.63%) of the extracts tested displayed low levels of mosquitocidal activity. The remainder of the extracts (17.85%) exhibited no bioactivity (0% mortality).The screening results have shown that in accordance with WHO standards, none of the crude extracts tested had exhibited greater than 60% mortality against the adult stages of the malaria vector Anopheles arabiensis.Even though there is adequate prevention measures and effective case management available, malaria remains one of the most important public health diseases resulting in approximately 300 million cases and an estimated 781 000 deaths annually [1]. Adult female anopheline mosquitoes have the ability to transmit malaria from an infected individual to a susceptible person. Vector control measures have, therefore, been established to control the transmission of the disease by targeting the carriers. Over the past few decades, the vector has however developed the ability to evade intervention measures, which target adult mosquitoes [2] thus exacerbating the problem for vector control programmes. The current vector control technique involves the use of residual insecticides which are sprayed onto walls and roofs of houses. This method, known as indoor residual house spraying (IRS) allows for a lethal dose of insecticide to adhere to the mosquito once it has rested on a sprayed surface [3].Research conducted over the years has produced four main class