Efficacy and persistence of Metarhizium acridum (Hypocreales: Clavicipitaceae) used against desert locust larvae, Schistocerca gregaria (Orthoptera: Acrididae), under different vegetation cover types Mohamed Ould Atheimine 1 *, Magzoub Omer Bashir 2 , Sidi Ould Ely 1 , Cherif Mohamed Habib Kane 1 , Sid’ Ahmed Ould Mohamed 1 , Mohamed Abdallahi Ould Babah 1 and Mounsif Benchekroun 3 1 Centre National de Lutte Antiacridienne, BP 665, Nouakchott, Mauritanie; 2 Faculty of Agriculture, University of Khartoum, Shambat, Sudan; 3 Laboratoire Agro-alimentaire et sante ´, Universite ´ Hassan 1er, Faculte ´ des Sciences et Techniques, BP 577, Settat 2600, Maroc (Accepted 5 February 2014) Abstract. The effect of vegetation cover (millet) on the efficacy and conidial persistence of Metarhizium acridum (Driver & Milner) J.F. Bisch., Rehner & Humber was evaluated in semi-field conditions using breeding cages (2 £ 2 £ 1 m). A mixed population of third- and fourth-instar desert locust larvae, Schistocerca gregaria Forsska ˚l, was used as a target. The insects were exposed in two different vegetation cover types classified as low (about 10%) and high (about 90%). Metarhizium acridum was used at a dose of 2.5 £ 10 12 conidia/ha in two different application volumes: 1 and 2 l/ha. Untreated insects kept in contact with treated vegetation were monitored to evaluate the persistence of conidia. The results showed that vegetation cover did not significantly (F ¼ 1.320; P ¼ 0.334) affect the efficacy of M. acridum. Under the high vegetation cover, the increase in the applied volume rate to 2 l/ha significantly improved the speed of mortality. Conidia persisted 6 days after treatment with a remarkable effect on untreated larvae exposed to the treated vegetation. In addition, the results of this study showed the efficacy of M. acridum in the low vegetation cover. With an important mass of vegetation, M. acridum conidia could persist even under high temperature conditions. Key words: Schistocerca gregaria, Metarhizium acridum, conidial persistence, vegetation cover Introduction In the current context of environmental protec- tion, the use of the fungus Metarhizium acridum ( ¼ Metarhizium anisopliae var. acridum; Bischoff et al., 2009) in the control of the desert locust could reduce the risks associated with the use of synthetic insecticides such as environmental pol- lution, development of insecticide resistance and *E-mail: mohamed.atheimine@gmail.com International Journal of Tropical Insect Science Vol. 34, No. 2, pp. 106–114, 2014 doi:10.1017/S1742758414000228 q icipe 2014