Effect of fertiliser application on yam nematode (Scutellonema bradys) multiplication and consequent damage to yam (Dioscorea spp.) under field and storage conditions in Benin

Studies were carried out at the International Institute of Tropical Agriculture ( IITA- Cotonou Station, Benin) and at Save ( central Benin), on the influence of chemical fertiliser application on yam nematode ( Scutellonema bradys) densities and damage in the field and in storage to three yam ( Dioscorea spp.) cultivars namely two D. rotundata cvs, TDr 131 and Ala, and one D. cayenensis cv, Kokoro. Treatments with nematodes ( 1000 per plant) and NPK, DAP ( Diamonic Phosphate) and KCl at rates of 300, 155, and 60 kg/ ha, respectively, were compared to un- inoculated and no- fertiliser control in field plots in terms of the damage to the crop and the multiplication of the nematode. At harvest, yield and the number of tubers per plant were not significantly affected by fertiliser application or nematode inoculation. However, the fertilisers suppressed nematode multiplication in tubers, especially DAP. In storage, tuber weight loss was recorded in all treatments. Weight loss was more pronounced in tubers from plots receiving fertiliser application than from those receiving none and when infected with S. bradys than when healthy, and mostly in tubers from infested plots which had received fertiliser. Nematode multiplication rates were greater in tubers during the first 3 months of storage, declining in the fourth and fifth months.