EFFECT OF STALK DESICCATION ON SUGARCANE RED ROT

The effect of drought conditions at planting time on sugarcane red rot , caused by Colletotrichum falcatum, was evaluated in experiments cond ucted under controlled conditions and in the field. For experiments un der controlled conditions, detached and topped mature stalks of five c ultivars were inoculated with conidia of C. falcatum then exposed to a 3-week desiccation treatment, followed by 3 weeks without desiccation , or maintained for 6 weeks without desiccation. Disease severity, ass essed as the number of nodes beyond which rot symptoms extended, numbe r of nodes rotted, internode rot severity, and a rot severity index, w as increased in five cultivars by exposure to desiccation. However, re sponse of individual cultivars varied for some disease traits assessed . In field experiments, C. falcatum inoculation alone did not reduce s pring shoot populations for seven cultivars. The lowest shoot populati ons occurred in plantings of inoculated stalks exposed to desiccation. Some cultivars were adversely affected by desiccation alone. These re sults demonstrate that red rot severity can be increased by the occurr ence of drought conditions during the initial growth processes of vege tatively propagated sugarcane stalks.