Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 3: 76 - 81. Published March 2008.
The effect of the application frequency and dose of Mancozeb on the management of potato late blight in Rwanda
J.B. Muhinyuza*^, S. Nyiransengiyumva**, J.C. Nshimiyimana* and W.W. Kirk***
*Institut des Sciences Agronomiques du Rwanda (ISAR), Rwanda; ** National University of Rwanda (NUR), Rwanda; *** Michigan State University (MSU), USA [kirkw@msu.edu].
Corresponding author: Email: mujohnbapt@yahoo.com; Tel: +250-530-145; +250-08436482,
ABSTRACT
Objectives: Experiments were conducted at the Institut des Sciences Agronomiques du Rwanda during two seasons 2005 B and 2006 A to test the efficacy of reduced rates of mancozeb in controlling potato late blight when applied at different frequencies on potato cultivar Kirundo, and establish an appropriate spray interval.
Methodology and results: The standard application program of Ridomil MZ at 2.5kg ha-1 application-1 alternating with Dithane M-45 at 2.0 kg ha-1 application-1 applied at a 10-day interval was compared with Dithane M-45 alone applied at 5, 10 and 15-day spray intervals at 50 and 100% of the manufacturer’s recommended application rate. Potato late blight was effectively controlled by the standard program of Ridomil MZ alternating with Dithane applied at 10-day intervals. The 5-day application interval program using Dithane alone at 50 and 100% of the recommended application rates was as effective as the standard program but the 10 and 15-day programs were not significantly different from the non-treated. Decline in yield was correlated with increase in foliar late blight severity.
Conclusion and application of findings: Effective control of potato late blight can be attained by combining host resistance and managed fungicide applications even in a variety that is relatively susceptible to potato late blight such as Kirundo. In dry years it would be reasonable to reduce applications of fungicide but to do so would require the development and establishment of a real-time potato late blight prediction model adapted to the region.
Key words: Fungicide, integrated disease management, Phytophthora infestans, plant resistance, potato cultivar
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