Flower and leaf damage of grapevines caused by the grape rust mite, Calepitrimerus vitis (Nalepa)

• The symptoms of damage on flower buds and leaves of grapevines caused by Calepitrimerus vitis (Nalepa) were examined.
• The damaged flower buds displayed retarded growth and became dried up.
• Malformed and bronzed leaves, and retarded shoot growth were observed.

The symptoms of damage on flower buds and leaves of grapevines caused by the grape rust mite, Calepitrimerus vitis (Nalepa) were examined in this study. The damaged flower buds displayed retarded growth and became dried up and some of the damaged flower clusters were curved. Not only symptom of damaged leaves such as malformed and bronzed leaves, but also retarded shoot growth was observed. Flower clusters (each flower cluster consisted of one main cluster and one side cluster) and leaves were collected to determine the relationship between degree of damage symptoms and density of the grape rust mite, which was measured by a modified washing and sieving method. The highest mean density (± SE) of C. vitis was found to be 672.6 ± 112.9 per flower cluster with the mid-level damage, while the lowest mean density was found to be 327.6 ± 55.5 per flower cluster with the high level damage. This was probably due to significant dispersal of grape rust mites from the highly damaged flower buds. Significantly higher numbers of C. vitis were found on the distorted leaves than on healthy ones.

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