The effects of various levels of cow manure (equivalent to 0–50 kg nitrogen/ha.) or ground limestone (equivalent to 0–5 tons calcium/ha.) on the expression of resistance of cassava, Manihot esculenta Crantz to the cassava mealybug, Phenacoccus manihoti Mat. Ferr., were investigated under semi-controlled conditions in the laboratory. The study was made on two varieties of cassava, Moudouma and MM79, characterized by different levels of resistance in terms of antibiosis and tolerance. The antibiotic component was evaluated by determining the intrinsic capacity for increase rc and tolerance by quantifying morphological and physiological modifications in the growth of plants induced by 2 months infestation by 100 mealybugs.

The antibiotic resistance of the two varieties was reduced by both fertilizers. However, the reduction was only significant at levels of 10 and 20 kg N/ha. and 1 and 1.51 Ca/ha. for Moudouma and MM79 respectively.

In both varieties, tolerance was increased by the addition of nitrogen and not modified by the addition of lime.

The integration of these results into traditional cassava crops systems has also been discussed.