Influence of temperature and high humidity duration on smut infection in pearl milletR PThakurauthorPanicles of Pennisetum americanum inoculated with Tolyposporium penicillariae maintained at a high RH (>95%) when exposed to post-inoculation temp. of <20°C for 8 h and >30°C for 3.5 h/day (range 15-32°) were not infected; those exposed to <20° for O h and >30° for 7.7 h day-1 (range 20-38°) developed 30% infected florets; and those exposed to <20° for 0 h and >30° for 5.4 h/day (range 26-33°) had 76% smutted florets. Of the temp. tested, min. temp. inhibited smut infection more than max. temp. With decreasing post-inoculation exposure time from 6.7 to O h/day at <20° there was a significant reduction in latent period from 23 to 11 d. Smut inoculated panicles exposed to high RH for 168-192 h produced max. infection (>50%). These results indicate that high RH periods of 168-192 h and a daily mean air temp. of c. 30° (range 25-35°) may be most favourable for smut infection, and that air temp. <20°, even for a few h/day, greatly reduce smut infection. The implications of these findings in screening P. americanum for smut resistance are discussedMillets1990The Indian Society of Plant PathologistsArticle