The use of chemical control and plant resistance against late blight of potato in Madagascar.FT L'utilisation de la lutte chimique et de la resistance varietale contre le mildiou de la pomme de terre a Madagascar.

摘要

Potato ( Solanum tuberosum L.) production in Madagascar was severely affected by the epidemic infestation of mildew ( Phytophtora infestans) during the years 2007-2008. Most of the potato varieties were severely affected. This calls for evaluation of anti-mildew products and resistance in the potato germplasm in the country. This study aimed at determining the efficacy of fungicides in terms of protectiveness and systemic actions; as well as inherent resistance of some potato varieties grown in Madagascar. Among the products tested, the mixture of protectant and systemic fungicides presented good efficacy level and higher economic returns. The best treatments are 1.5 kg ha -1 of mancozebe based dithane plus 1.5 kg ha -1 of fosetylaluminium based d-athlete, and 1.5 kg ha -1 of dithane plus 1.5 kg ha -1 of metalaxyl based ridomil plus manebe. Application of these products resulted in a benefit cost ratio of 3. Varieties which showed considerable resistance included CIP 395 015.6, CIP 395 111.13 and CIP 396 236.20, all yielding >20 t ha -1. However, their resistance levels need to be monitored regularly.