Trichogramma chilonis (Hymenoptera : trichogrammatidae) as a biological control agent of Chilo sacchariphagus (Lepidoptera, Crambidae) in Reunion Island : initial field trials

International audienceThe spotted stalk borer, Chilo sacchariphagus Bojer, is a major pest of sugarcane in southern Asia, the Indian Ocean islands and Mozambique in southern Africa. Since 1999, a biological control programme has been developed on this pest in Reunion Island through a partnership between research and development organisations. Trichogramma chilonis Ishii has been shown to be the most naturally efficient parasitoid of the borer in Reunion, following a comparison of the bionomics of different strains of T. chilonis, and one strain was selected for mass production and field release testing. In 2002, two distinct sites, Savannah (SAV) and Sainte-Marie (SMA), were chosen for field experiments. At each site, plots were treated with releases of 150 000 T. chilonis per hectare and compared with untreated plots. In both plots, efficacy of these releases was assessed through damage to sugarcane internodes and mass of millable stalks at harvest. In treated plots, the percentage of bored internodes at harvest was 45% less than the controls at SAV and 36% at SMA. The mean stalk mass was 14% higher in treated plots at SAV, and 12% at SMA, corresponding to increases of 15 and 12 tons of cane per hectare, respectively. These results are presented and improvements in a new trial are suggested