PRACTICAL ASSESSMENT OF PEARL-MILLET (PENNISETUM-GLAUCUM) CROP LOSS CAUSED BY GRASSHOPPER PESTS (ORTHOPTERA, ACRIDIDAE) - A MAJOR OUTBREAK IN NORTH-WEST MALI

The impact of Sahelian grasshopper species on short cycle pearl millet (Pennisetum glaucum) was studied at two sites in north-west Mali and techniques of crop loss assessment were investigated. At one of these sites an on-farm study was carried out with the co-operation of seven village farmers. The grasshoppers Diabolocatantops axillaris (Thunberg ) and Kraussaria angulifera (Krauss) were the principal destructive sp ecies, primarily causing grain loss through their feeding upon millet heads. Leaf damage was found to be sustainable to a high level before influencing yield, although direct grain loss through head damage was shown to be an important determinant of final yield. It was concluded that the best means of determining the yield loss attributable to gras shopper attack for late-season patterns of damage was to estimate head damage immediately prior to harvest. In this estimate, heads were ass igned to one of ten classes according to the severity of the damage. S tudies at a second site demonstrated the existence of a linear relatio nship between estimates of head damage and actual grain weight loss. O n the basis of these findings it is concluded that the average loss of yield incurred as a result of grasshopper attack in the study village , Mamaribougou Freybe, was 25.7% + 3.0, -2.5. A system is proposed by which such village-level crop loss estimates may be undertaken.