ELSEVIER Field trials of fipronil for control of Rhammatocerus schistocercoides (Rehn, 1906) hopper bands in Brazil Michel Lecoq* and Gilles Balanqa Centre de coopkration internationale en recherche agronomique pour le dkveloppement, BP 5035, 34032 Montpellier Cedex 1, France Field trials in the state of Mato Grosso (Brazil) assessed the efficacy of tipronil against Rhammuto- wms ,schistocercoidc.s hopper bands (8th instar) in natural vegetation within the context of a prevcn- tivc control strategy. Thirteen experimental plots, with 14 hopper hands. were sprayed at doses ranging from 2.15 to I I.8 g a.i./ha. Mortality increased with higher doses in a shorter time, hut all tested doses resulted in 100% mortality within one to four days. The dose to control hopper bands depends on the speed of control required, according to the potential threat to crops: preventive control in natural vegetation (4 g a.i./ha) or curative control in crops (X g a.i./ha dose could bc used). 0 1998 Elsevier Science Ltd. All rights reserved Keywords: Rhammatocerus schistocercoides; grasshopper control; fipronil Rhammatoccrus .schistocercoi&s (Rehn, 1906) [Orthoptera, Acrididae, Gomphocerinae] is an important pest, devastating sugarcane and rice crops (Carbonell, 1988; Cosenza et al., 1990) in South American savanna and wooded savanna areas, mainly in the state of Mato Grosso (Brazil). Damage has also recently been reported in Colombia and Venezuela (Cardenas and Devia, 1995; L&n, 1996; Martinez and Gomez, 1996). R. schistocercoides is a univoltine grasshopper. In Brazil hopper development is very slow (8-9 instars), from late October to late April, during the rainy season. The first adults appear by mid April and remain immature until late August, whatever the rain. Sexual maturation is achieved in one month and laying occurs from late September to late October (likely no more than three clutches per female). The behaviour is very gregarious: hoppers form bands (covering tens to thousands m2, with up to 5,000 hoppers/m’) and adults form swarms (covering thousands m7 to several hectares when landed) that partially leave the breeding areas to wander throughout the natural vegetation and crops (Lecoq and Pierozzi Jr, 1994a,b, Launois-Luong and Lecoq, 1996. Miranda el al., 1996). Grasshopper control in Brazil relies on application of pesticides, mainly malathion and fenitrothion (Cosenza ct al., 1990, 1994). A recent recommended control strategy involved looking for hopper bands in the savannas with sandy soil surrounding areas of crops during the seven month rainy season, spot treating hopper bands, and, if necessary, treating *Corresponding author: Fax: (33) 04 67 41 09 58 Email: Iecoq@cirad.fr hopper bands present in crops (Lecoq et al., 1997; Miranda et al., 1996). This study was conducted to determine the effects of fipronil treatments on hopper bands, and to estab- lish how to use this phenyl-pyrazol insecticide (dose and application technique) according to the recom- mended control strategy. Several laboratory and field tests had already shown that doses ranging from 0.6 to 20 g a.i./ha were effective against many african, asiatic and north american grasshopper and locust species (Butler and Du Preez, 1994; Price et al., 1994; Megenasa and Muinamia, 1994; Rachadi ct ul., 19Y5; Rachadi and Foucart, 1996: Lockwood et al., lY96; Balanqa and de Visscher, 1997b). Materials and methods Study area The study was conducted in a IO0 km 7 area in central-western Mato Grosso. in Chapada dos Parecis, 370 km NW of Cuiab& around the ALCOMAT factory (14” 16’ S, 59” 14’ W), a typical R. schistocercoides outbreak area (Lecoq and Pierozzi Jr, 1994a). The landscape is uniform with gently rolling ground, interlaced with a few rivers edged with well developed gallery forests. The main plant communities arc pure savannas and bushy or forested savannas, locally called ‘campo’, ‘campo-cerrado’ and ‘cerrado’, depending on the extent of the woody plant layer. The first two communities are natural biotopes for R. schistocercoides which can be divided into two categories: breeding biotopes that are usually on Crop Protection 1998 Volume 17 Number 2 105