FIELD INCIDENCE, FUNGICIDAL EFFICACY AND NUMBER OF FUNGICIDAL SPRAY AGAINST LATE BLIGHT OF POTATO

Abstract

A study was made on the field incidence and management of late blight of potato due to Phytophthora infestans during 2006-2007 cropping season. Survey of potato field at Dinajpur district revealed that late blight was very much frequent in all over the surveyed upazillas during 2006-2007 cropping season. Of them, Parbatipur (56%) was the worst affected by late blight followed by Birampur (49.7%), Khansama (48.6%), Birgang (43.3%), Birol (39.6%), Hakimpur (39%) and Fulbari (37.6%). During 2007-2008 cropping season some upazillas of Dinajpur district were found apparently free from late blight incidence viz. Dinajpur sadar, Birgang, and Kaharol. Some of upazillas less affected viz. Khansama, Parbatipur, Chirirbandar, Fulbari and Bochagang. Of them, Nawabgang (26%) was the worst affected by late blight followed by Birol (25.8%) and Birampur (23.3%). Ridomil was widely used fungicide in controlling late blight throughout the surveyed area. Altogether the effectiveness of five fungicides was tested against late blight. All the fungicides significantly reduced the late blight incidence over control. The lowest plant infection was recorded for fungicides namely, Ridomil gold and Acrobat. The role of number of fungicidal spray in minimizing the incidence of late blight of potato indicates that the number of fungicidal sprays had significant influence on late blight incidence. The incidence of late blight infection was highest in single spray of fungicides and it decreased gradually with increasing number of fungicidal sprays.