Attempts to isolate the causal agent of cotton leaf roll disease from infected cotton leaves collected from Saraburi Province were done by using seven chemical and physical isolation methods. It revealed that virus particles were observed only in the preparation obtained from employing the purification procedure modified from that of Rowhani and Stace-Smith (1979) for potato leaf roll virus. After the partially purified virus preparation was centrifuged through 10-40 % linear sucrose density gradients at 38,000 rpm. for 240 min, a single, opaque band was observed at 35-40 mm. below the meniscus. This band contained flexuous rod particles about 600-700 nm. in length when observed under the electron microscope. The virus particles appeared to be singly scattered when they were stained with 2 % phosphotungstic acid but they appeared in clusters when 2 % uranyl acetate and 2 % ammonium molybdate were used. The purified virus preparation had 320-200 nm. absorption spectrum characteristic of that of nucleoprotein with a A260/A280 value of 1.159.

Parasitic (seedling disease, angular leaf spot, fusarium wilt--root knot nematode complex, verticillium wilt) and nonparasitic diseases (crinkle leaf) of cotton in Arkansas and their control are discussed in this leaflet.

Abstract: Parasitic (seedling disease, angular leaf spot, fusarium wilt--root knot nematode complex, verticillium wilt) and nonparasitic diseases (crinkle leaf) of cotton in Arkansas and their control are discussed in this leaflet.

Placing the inoculum together with the seed was more effective method of inoculation in screening cotton for resistance to Sclerotium rolfsii Sacc., Rhizoctonia solani Kuhn and a combination of both than by mixing the inoculum with the soil. High inoculum levels yielded a corresponding increase in the number of plants that were infected regardless of inoculation techniques and pathogens used. Four to 16-day old plants were susceptible to both pathogens inoculated singly. However, when inoculated in combination, plants were infected up to 24 days after planting. Inocula remained infective up to 14 days in the soil