The Tree Locust, Anacridium melanorhodon melanorhodon (Walker 1870) (Orthoptera: Acrididae) is a serious pest of gum Arabic tree, Acacia senegal in Sudan and elsewhere in Africa. Efficacy of Metarhizium anisopliae var. acridum, strain IMI 330189 alone and its mixture with Neem oil was investigated for two seasons (2006/07 and 2007/08) against the Tree Locust in the North Kordofan State of Sudan. The locust nymphs (4th instars) were treated with Metarhizium, Metarhizium/Neem mixture, Neem, and Malathion used as standard synthetic locusticide. The nymphs were directly sprayed in the field (50 x 50 m plots) with the test materials in a plantation of Acacia senegal using a hand-held micro-ulva sprayer. Nymphs samples were taken 24 hours after application from each treatment, placed in cages and observed for mortality. For the two seasons, respectively, mortality equivalent to 74.2% and 94.8% was obtained in locusts treated with the Metarhizium/Neem mixture in contrast to 64.2% and 81.5% mortality obtained in those treated with Metarhizium alone, respecting the previous season¿s order, during a three week period. These findings clearly reveal that mixing Metarhizium with Neem could enhance locust mortality and accelerate killing capacity compared to either Metarhizium or Neem when used alone. Among the treated plots, in comparison to the control, an obvious reduction in locust density was observed from the 3rd day after application in plots treated with Malathion (83.18%). The reduction in locust density in Metarhizium plots was similar to that observed in Malathion plots 12 days after application and this trend continued until day 16, while the efficacy decreased in Malathion plots. The study concluded that the use of Neem oil as a mixture with Metarhizium in the field boosts the killing speed. (Texte intégral)