Studies on the Period of Infection with Citrus Canker of Spring Leaves and Fruits

Abstract

Degree of infection with citrus canker (Xanthomonas citri (Hasse) Dowson) varies according to the aging of leaf and fruit.
This experiment was carried out for determine the sensitive period of spring leaves and fruits. In the spring leaves, various ages of young leaves of some citrus species, Fukuhara, Natsudaidai and Satsuma oranges, were inoculated through stomata with bacterial suspension containning 10⁸ cells per ml. While the age distribution and its successional changes was investigated every 5 days during the growing period of spring leaves. And the period of stomatal infection was determined by the results of the stomatal inoculation test and the distribution of leaves ages.
In the fruits, using Satsuma orange fruits, stomatal and wound inoculation was made every weeks with bacterial inocula containing 10⁸ cells per ml from the beginning of June to the middle of September.
With stomatal inoculation, the spring leaves of all tested species, were sensitive while middle aged leaves were many, from 10 to 50 days (the most sensitive period, from 20 to 40 days) after the orange buds were out.
In the fruits of Satsuma orange, stomatal infection was caused from the beginning of June to the middle of August. The most sensitive period was July. Wound infection was caused during the middle of June to the end of August. The most sensitive period was during the middle of June to the middle of July.