Efficacy of Isolated Nomuraea rileyi and Spinosad against Corn Pests under Laboratory and Field Conditions in Egypt

Abstract

Isolates of the entomopathogenic fungus, Nomuraea rileyi and spinosad were tested against the corn insect pests: Ostrinia nubilalis, Chilo agamemnon and Sesamia cretica under laboratory and field conditions. Results obtained showed that the LC50 of N. rileyi for O. nubilalis, C. agamemnon and S. cretica were 124, 146 and 159 conidia/ml under laboratory conditions. The corresponding figure for Spinosad was 166, 179 and 185 microgram/ ml (µg/ml. Under field conditions, results showed that during season 2011, the percentage of O. nubilalis, S. cretica and C. agamemnon infestations were significantly decreased in plots treated with N. rileyi to 25±3.2, 21±2.4, and 24±2.3 individuals after 120 days after the first application as compared to 97±3.3 in the control. When spinosad was applied in the field, the percentage of infestations was significantly decreased to 26±3.3 as compared to 99±1.3 individuals in the control during both seasons. During the harvest season, the corn weight was significantly increased to 3822±45.6 and 3940±60.4 kg/Feddan (Feddan=2400m2) in the plots treated with the fungus N. rileyi as compared to 2810±40.9 and 2710 ±73.2 Kg/Feddan in the control plots. Among plots treated with spinosad the yield significantly increased to 3000 ±60.7 and 3129 ±84.1 kg/Feddan during season 2011 and 2012, respectively.