The effect of mancozeb wp (wettable powder) on mancozeb adhesion and melanose control after application on wet citrus trees.

Abstract

Mancozeb wp was sprayed on wet citrus trees to examine the effect on mancozeb adhesion and melanose control. In the first trial, mancozeb wp was sprayed on wet fruits, and the amount of mancozeb adhesion was analyzed as methyl derivative by HPLC method. The amount of mancozeb adhesion on wet fruits was 7.2 μg/cm², approximately half of that on control (dry) ones. In the next trial, mancozeb wp was sprayed on citrus trees immediately after trees were sprayed with 10 liters of water per tree, and the amount of mancozeb adhesion on leaves and the control of melanose on fruits were examined one month after the application. Artificial inoculation was made by spraying 10⁶ conidia/ml water of Diaporthe citri on fruits picked up from treated trees. Mancozeb adhesion on leaves of the wet and dry citrus trees were 0.6 and 1.2 μg/cm² while their disease severity (0-100 scale) were 16.1 and 7.4, respectively. Similar results were also obtained in field tests in 2001 and 2003.