Some aspects of the epidemiology of Maize streak virus (MSV) genus Mastrevirus concerning virus incidence, vector populations and some environmental factors were investigated in field experiments conducted over a three year period (2000–2002) at Samaru, northern Nigeria. Significant positive correlations were obtained between number of leafhoppers caught and MSV incidence and age of plant at infection and also with temperature. Also significant negative correlations were obtained between MSV incidence and mean relative humidity; between number of leafhoppers and age of plants and with mean rainfall. Leafhopper vectors caught included Cicadulina arachidis China, C. mbila Naude, C. triangula Ruppel and C. similis China, in order of abundance. Leafhopper incidence was highest in the months of September and October.

Intensive surveys conducted at Samaru and its environs in the northern Guinea Savanna of Nigeria between October 2000 and September 2002, indicated that Bemisia tabaci (Genn.) infests forty two (thirty three cultivated and seven wild) species of plants. Twenty nine of the plants were found in upland, two in the lowland and eleven in both upland and lowland (fadama) areas. Heavily infested plants were distorted, chlorotic and stunted. Symptoms of virus infection were associated with some of the infested plants. This is the first comprehensive report of hosts of B. tabaci in Nigeria.

Field surveys were undertaken in 1997–1999 across five ecological zones in Nigeria to collect isolates of Maize streak virus (MSV), genus Mastrevirus. Apart from maize (Zea mays L.), 15 other grass species were found with MSV symptoms in Nigeria. These hosts showed two types of symptoms viz: mild (with or without mottle) or severe (typical symptoms in maize). When Cicadulina storeyi China was used to attempt transmission of these isolates of MSV to seedlings a susceptible maize hybrid CML 254 X CML 247, six isolates were not transmissible to maize. Seven isolates that were transmissible to maize produced mild symptoms. The viral agents causing typical or severe streak symptoms in Axonopus compressus (Sw.) P. Beauv., Brachiaria distichophylla (Trn.) Stapf, Dactyloctenium aegyptium (Linn.) P. Beauv. and Setaria barbata (Lam.) Kunth produced symptoms that were typical of MSV in farmers fields, when transmitted to maize. Out of 33 plant species that seedlings were challenged with MSV, only eight proved susceptible. Four of them showed mild symptoms while the other four showed severe symptoms of MSV. Only three isolates collected during the surveys did not react with a MSV polyclonal antiserum produced in mice in Double Antibody Sandwich-Enzyme-Linked Immunosorbent Assay (DAS-ELISA). These isolates were found in Andropogon gayanus Kunth (from Kaduna), Thelepogon elegans Roth ex Toem & Schult (from Kadawa) and Rottboellia cochinchinensis (Lour.) Clayton (from Jos) exhibited mild streak/mottle symptoms. Specific monoclonal antibodies, raised against MSV, reacted with 12 out of 25 samples tested. The DAS-ELISA data also showed significant variation in concentration of the virus in the different plant hosts. The relationship dendogram through SDS-PAGE among eight purified virus isolates show 55–90% variation. At 0.55 coefficient of similarity, the dendogram divided the samples into two groups while at 0.9 coefficient of similarity, the 8 isolates were identified as distinct genetic entities.

A survey was conducted in February of 2004 on the outbreak of stem rot and wilt disease of pepper at the Kitabawa/Danzakara and Ajiwa irrigation sites in Northern Nigeria. Laboratory investigations revealed that it was elicited by Phytophthora capsici Leon. The disease caused severe loss in yield and USD 1 700.00 to USD 3 200.00 loss in revenue/ha. The disease was probably further aggravated by the presence of Fusarium sp. as well as ecto- and endoparasitic nematodes. Reasons for outbreak were elucidated and solutions proffered.