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The aim of this study was to investigate under a controlled environment, the effect of temperature on the survival and infectivity of PseudotheraptusdevastansDistant, a cassava anthracnose disease vector. The insect P. devastanswas collected from young cassava (Manihot esculentaCrantz) field plots, at the International Institute of Tropical Agriculture, (IITA), Ibadan, Nigeria. A mixture of the different developmental stages of eggs, first to fifth instar nymphs, and adults, were incubated in controlled environment chambers, under various constant temperatures of: 15, 17, 22, 25, 27, 30, and 35°C. Relative humidity at different temperature conditions were recorded and maintained at 90%, 85%, 80%, 75%, 70%, 65%, and 60%, respectively. A significant increase in insect survival was observed between 22 and 27°C temperature conditions while a significant decrease in survival was observed at 15°C and above 30°C. Lesion number, lesion diameter and infectivity among the insect stages varied as a function of temperature and relative humidity. Infectivity was highest at 22–25°C maintained at 75–80% RH and lowest at 15°C and above 30°C maintained respectively, at 65% RH and 90% RH. There was considerable low vector infectivity due to low survival of the insects at extreme temperatures.

Thirty-five cassava (Manihot esculentaCrantz) genotypes from the International Institute of Tropical Agriculture (IITA), germplasm collection were planted in May 1992 under natural disease infection conditions, at the IITA field plots at Ibadan, Nigeria. The genotypes were evaluated at monthly intervals for six months, for incidence and severity of cassava anthracnose disease (CAD), cassava bacterial blight (CBB) and African cassava mosaic virus (ACMV). The effect of the pathogens on yield was also evaluated twelve months after planting (MAP). CAD, CBB and ACMV incidence and severity were significantly different (P<0.05) among the cassava genotypes at 3 and 6 months after planting. ACMV incidence and severity reached the maximum levels at 3 MAP while CAD and CBB had a low incidence and severity at that period but exhibited a high disease symptom expression at 6 MAP. Yield parameters (plant stand, tuber number, tuber weight and tuber dry matter) differed significantly (P<0.05) between the cassava genotypes. ACMV and CBB severity was negatively correlated with tuber number (r= −0.54 and r= −0.62 respectively). CAD severity was negatively correlated with tuber number (r= −0.46) and tuber weight (r= −0.63). Percentage dry matter was significantly correlated with ACMV severity (r= 0.71), CBB severity (r= 0.63) and CAD severity (r= 0.42). There was also a significant correlation between CBB and ACMD severity (r=0.46) and CBB and CAD severity (r=0.62). Tuber number and yield were significantly correlated (r=0.60), while% dry matter content and root rot showed a significant negative correlation (−0.42).