A survey of sorghum downy mildew in sorghum in the Sudano-Sahelian Savanna zones of Nigeria

Abstract

An extensive survey was conducted across the 13 states constituting the Sudan and Sahel savanna agro-ecological zones of Nigeria to determine the occurrence and distribution of sorghum downy mildew in sorghum during the 2008 growing season. The survey was conducted at two different stages of the crop development; seedling and dough stage. The first survey was in early July while the second was carried out in late September. Three farmers’ fields were critically investigated at every stop on a road system. During the first survey, a total of 97 farmers’ fields in 36 locations were investigated while 110 sorghum fields in 37 locations were visited in the second survey.
Average incidence (%) of the disease was obtained from a sample of 100 plants selected using simple random sampling technique from each of the three farms visited per stop. Results of the survey (16.20 and 9.64% and 3.28 and 1.16% during the first and second visits in the Sudan and Sahel savanna AEZs respectively) indicated that the disease was present only at the seedling stage and virtually absent at flowering stage .In the areas where it was noticed at the juvenile stage the incidence was more prevalent in the Sudan than in the sahel savanna regions. The results also revealed that there was a relationship between soil type (which was mostly sandy loam) and disease incidence. Disease incidence was relatively higher on sandy loam soil than other soil types. The prevalence was generally low, but efforts should be made towards controlling the spread of the disease further. Farmers should be advised to use improved cultural practices like early sowing, seed dressing with the sole aim of reducing the disease.

Keywords: sorghum downy mildew, incidence, distribution, Sudan and Sahel savanna agroecological zones