Qualitative determinations of R. solani in infected plants are made by isolations from infected host plant tissues. Infected plant tissues are cut in pieces of 5 cm, washed in running tap water to eliminate any attached organic debris, and blotted to dry. Small samples of plant tissue (0.5 cm of length) are then cut from the lesions and transferred to an isolation medium, which can be either general (e.g. alkaline water agar) or selective (e. g. modified Ko & Hora medium). The alkaline water agar medium provides a faster way of isolating the fungus than other general media since successful isolation of R. solani can be obtained after 24 h of transfer (Guttierrez et al., 1997).
Quantitative determination of R. solani from soils to estimate the inoculum density are based on the saprophitic and/or pathogenic competitive abilities of the fungus. Methods developed from this principle included the burial and subsequent recovery of various substrates as baits for Rhizoctonia. The baits include suscetible host plants, autoclaved seeds, stem segments such as flax, buckwheat, bean, cotton and cereal straw, and even agar baits. Other methods include different soil sieving procedures combined with selective media for the isolation of R. solani from soil. A subsequent method using a multiple-pellet soil-sampler was developed for quantitative estimation of propagule density of R. solani based on placement of weighed amounts of soil, or soil pellets on water agar supplemented with chloramphenicol, or on selective media (Hennis et al. 1978, Ko & Hora 1971, Castro et al. 1988).