The influence of climatic features on distribution and infection of root-knot nematodes <i>Meloidogyne</I> spp, n cowpea growing areas in Nigeria

Abstract

The effect of climatic features on distribution and infection of root knot nematodes was investigated in 248 cowpea growing areas in 31 states and the Federal Capital Territory of Nigeria. The studies revealed pronounced incidence of Meloidogyne javanica (65.5%) at high altitude of 500-2000 m, high mean annual maximum temperature of 32-40 °C, low mean annual minimum temperature of 11-18 °C, low mean annual precipitation of 0.1-1530 mm and in hot Sudan savannah vegetation of six months or less of wet and dry season, prevailing in the Core North (North east and North west) of the northern region. In contrast, M. incognita (83.1%) was overwhelmingly dominant at low attitude of 15-650 m, mean annual maximum temperature of 24-27 °C, mean annual minimum temperature of 21-23 °C, mean annual precipitation of 1170-4700 mm and in warm humid forest vegetation of 8 months or more of wet season and 4 months or less of dry season, operating in the southern region (Southeast, Southwest and Southsouth). The two species (M. incognita) (44.2%) and M. javanica (51.7%) were, however, common at intermediate altitude of 305-1859 m, moderate mean annual maximum temperature of 29-32 °C, moderate mean annual minimum temperature of 18-21 °C, moderate mean annual precipitation of 800-2000 mm and in moderate Guinea savannah vegetation of 7 months of wet season and 5 months of dry season, prevailing in the Middle belt (North central). The distribution of M. arenaria though sparse (4.1%), followed that of M. incognita in relation to altitude, temperature, precipitation and vegetation. In overall distribution, M. incognita (51.8%) was more widespread than M. javanica (44.1%). The occurrence of pure population of M incognita (31.9%) and M. javanica (37.1%) was encountered. Meloidogyne arenaria was never found as a pure population or as a mixture with M. javanica but with M. incognita (2.0%) or with M. incognita and M. javanica together (4.0%). The mean galling infection by the two species was significantly more severe in the humid forest southern region (11-50% of the root system galled) than in the dry Sudan savannah Core North (1-30% of the root system galled). Generally, Meloidogyne incognita caused more severe mean galling infection (11-30% of the root system galled) than M. javanica (1-10% of the root system galled). The polarized ecological distribution and infection of the M. incognita and M. javanica in the present studies show the climatic preference of the nematodes, and gives a guide in targeting a workable control strategy.

Keywords: Climatic features, cowpea, distribution, infection, root-knot nematodes.

Ife Journal of Science Vol. 8 (2) 2006: pp. 185-192