Spatial distribution of populations of solitarious adult desert locust (Schistocerca gregaria Forsk.) on the coastal plain of Sudan
1 Densities of solitarious adult desert locusts were measured on regular grids of up to 126 sample sites in the southern part of the coastal plain of Sudan during the winters of 1999/2000 and 2000/2001. Geostatistical procedures were used to characterize spatial dependence of locust density, to evaluate the possibility of estimating locust densities at unvisited sites, based on information obtained at surveyed sites, and to create density maps.
2 Sample variograms indicate that population densities were spatially correlated over ranges from 5 to 24 km. The range of spatial correlation decreased as dry conditions towards the end of the rainy season concentrated the locusts in contracting areas of sufficient humidity and availability of green vegetation. The rather small ranges of spatial correlation indicate that sampling needs to be conducted at a refined scale (< 24 km between sample points) to avoid missing hot spots of desert locust.
3 Locust densities were highly correlated with cover abundance of the wild plant Heliotropium arbainense and cultivated millet, Pennisetum typhoidum. The association of locusts with these host plants can be used to target sampling and enhance detection chance.
4 The relationship between sampling intensity and kriging variance was explored. Implications for monitoring of desert locust are discussed.
Document Type: Research Article
Affiliations: 1: Wageningen University, Department of Plant Sciences, Laboratory of Entomology, PO Box 8031, 6700 EH Wageningen, the Netherlands, 2: Wageningen University, Department of Plant Sciences, Group Crop and Weed Ecology, PO Box 430, 6700 AK Wageningen, the Netherlands and 3: Wageningen University, Biometris, PO Box 100, 6700 AC Wageningen, the Netherlands
Publication date: 2004-08-01