Submitted to: Archives of Phytopathology and Plant Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/14/2012
Publication Date: 7/30/2012
Citation: Nyankanga, R.O., Njogu, M.K., Muthomi, J.W., Olanya, O.M. 2012. Efficacy of fungicide combinations, phosphoric acid, and plant extract from stinging nettle on potato late blight management and tuber yield. Archives of Phytopathology and Plant Protection. 45:1449-1463. Interpretive Summary: Farm profitability can greatly be increased by reducting production costs associated with late blight management. We assessed the efficacy of fungicides, phosphoric acid, plant extract and their combinations for the management of potato late blight. The application of metalaxyl alternated with phosphite resulted in the greatest suppressive effects on late blight. The average disease severity ranged from 3.5-34% in 2008, and 4.7-50% in 2009 at Tigoni location and relative area under disease progress curves for the same locations ranged from 5-40 and 5-50% in 2008 and 2009, respectively. With the exception of plant extract, the treatment combinations resulted in moderate potato tuber yield, implying that selective treatments can readily be applied for effective management of late blight management under field conditions.
Technical Abstract: Late blight, caused by Phytophthora infestans is a major constraint to potato production. Inadequate management of the disease has often resulted in heavy losses in various production regions. We assessed the efficacy of fungicides, phosphoric acid, and stinging nettle plant extract combinations for late blight control at two locations in Kenya. Disease severity, relative area under disease progress curves (AUDPC), pathogen lesions, and tuber yield were quantified during the 2008 and 2009 cropping cycles. The application of metalaxyl alternated with phosphate resulted in the greatest suppressive effects on late blight. The average late blight severity ranged from 3.5-34% in 2008, and 4.7-50% in 2009 at Tigoni location. RAUDPC for the same locations ranged from 5-40 and 5-50% in 2008 and 2009, respectively. Similar levels of late blight severity were recorded at Marimba location in both years. Lesion growth and pathogen lesion numbers on potato plants differed significantly (P<0.05) among treatments. Fungicides, phosphoric acid and stinging nettle extract resulted in various levels of late blight control. Potato tuber yield varied among treatments. Phosphoric acid treatment resulted in significantly (P<0.05) greater tuber yield compared to metalaxyl at both locations. Plant extracts from stinging nettle resulted in the lowest tuber yield compared to other treatments with the exception of the untreated control. Fungicides, phosphoric acid, stinging nettle extract and their combinations can be readily effective in the suppression of late blight severity and pathogen lesions with moderate increases in tuber yield.