Can NDVI GAC imagery be used to monitor desert locust breeding areas?

AVHRR GAC NDVI values for the locations and dates of all desert locust Schistocerca gregaria populations reported during 1985–1986 were found to be similar to or lower than values for the same location and times of year during 1981–1994, using a variety of novel indices. It was concluded that this was due to a poor relationship between NDVI values and rainfall in very arid areas, in the light of an analysis of the relationship between NDVI data and interpolated rainfall. Low NDVI values at the time of locust observations were not associated with unusually high levels of cloud, as measured by the CLAVR channel of the imagery. Results were similar for observations of tree locusts Anacridium spp. and migratory locusts Locusta migratoria included in desert locust survey reports, but there was evidence of a positive relationship between NDVI and the presence of grasshopper populations, probably because grasshoppers were found in areas with higher rainfall.