Change in the outbreak of rice diseases in mechanized transplant cultures.
The rapid spread of mechanization during the last 10 yr has increased seed-borne and soil-borne diseases in nursery beds, and changed disease outbreaks in the field. Blast (Pyricularia oryzae) has increased while sheath blight [Corticium sasakii] and bacterial leaf blight [Xanthomonas campestris pv. oryzae] have decreased. Other diseases showing increasing incidence are bakanae (Gibberella fujikuroi) and bacterial grain rot (Pseudomonas glumae), while there is a decrease in downy mildew (Phytophthora [Sclerophthora] macrospora). The incidence of blast, bakanae, brown spot (Cochliobolus miyabeanus) and bacterial grain rot has increased in box nurseries; appropriate control measures are outlined. The incidence and control of soil-borne damping-off fungi in box nurseries are also described.