Efficacy of BotaniGard (<i>Beauveria bassiana</i>) Against Whiteflies on Poinsettia and Dahlia

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Efficacy of the entomopathogen fungus, <i>Beauveria bassiana</i> (BotaniGard) was compared with conventional insecticides against whiteflies on Poinsettia (<i>Euphorbia pulcherrima</i>) and Dahlia (<i>Dahlia coccinea</i>) in Maranque plant located at Doni in Eastern Shoa zone of Ethiopia between December 2010 and March 2011. The experimental site measuring 1250 m^² was divided in 6 bays. Three bays in alternative fashion were allocated for treatment with the test pesticide, BotaniGard and the other three for spraying with the conventional insecticides according to the routine practice of the farm. BotaniGard was applied at the concentration of 0.15% by mixing 150 ml of the product with 100 l of water weekly for the first ten weeks and twice weekly thereafter until the termination of the experiment. Mean whitefly number per treatment was calculated to examine population fluctuation in adjacent BotaniGard and control treatments of both Dahlia and poinsettia. To assess presence of statistical differences in whitefly population between treatments as well as between plant species, a student t-test was used using counts recorded from each of the 12 cards per treatment at the different weeks. Population of whiteflies was generally low in both plant species until 17 January 2011 without appreciable difference in whiteflies number between the BotaniGard and the conventional insecticides. Whiteflies number increased after 17 January in both plant species and peaked on 7 February 2011. Pest population in BotaniGard treated bed was lower than conventional insecticides treated bed during this period in both plant species. Whiteflies population in Poinsettia fluctuated between 3.9 and 42 per trap compared to between 0.6 and 24.8 in Dahlia in the conventional insecticide treatment. On BotaniGard treated plot, whiteflies number fluctuated between 2.5 and 17.6 in poinsettia and between 1.8 and 12.5 in Dahlia. This difference between Dahlia and poinsettia was significant (P<0.05) in 5 out of 12 sampling dates in the conventional treatment and in 7 out of 12 weeks in BotaniGard treatment. Dahlia was less susceptible to whiteflies and BotaniGard resulted in lower number of whiteflies than the conventional insecticide treatment. Hence, BotaniGard may be used as a viable alternative to reducing the use of chemical insecticides in the management of whiteflies in green house produced plants.