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.
A semiselective medium for isolating benomyl-resistant strains of strawberry anthracnose fungus Glomerella cingulata (Stoneman) Spaulding et Schrenk was developed, and the infection site and habitat of the fungus were investigated. Potato sucrose agar was used for basic medium and supplemented with 50 mg/l benomyl, 30 mg/l triflumizole, 100 mg/l oxgall and 50 mg/l streptomycin sulphate. The growth of benomyl-resistant strains was not inhibited with semiselective medium, but the growth of other fungi and bacteria was inhibited. G. cingulata was isolated from leaflets, petioles, crowns of latently infected plants, and dead plants at high frequency. The fungus was also isolated from the potting medium of diseased plants. Isolation frequency from leaflets, petioles and bases of petioles in the outer leaf position on latently infected plants was higher than from those on inner leaves. Nursery plants inoculated by drenching discolored, wilted and died without black leaf spots symptom. When drench-inoculated with the conidia suspensions (105–106/ml), whole plants wilted and died. Wilt symptom was still observed when plants were inoculated with the suspensions (<102/ml). The fungus was isolated from roots at high frequency. After conidia suspensions (105/ml) of G. cingulata were poured on peat-vermiculite, sawdust and sand for nursery medium, the fungus was consistently isolated from those media over a one-month period. These results showed that G. cingulata had latently infected leaflets, petioles, bases of petioles and crowns of strawberry plants, and had survived in nursery media over a one-month period in the absence of plants.
In 2002 and 2003, sensitivity to thiophanate-methyl (TM) of Fusarium spp. and Microdochium nivale, causal agents of Fusarium head blight, isolated from wheat in Aomori Prefecture was tested in vitro. Five of 74 isolates in 2002 and 1 of 361 isolates in 2003 were identified as F. culmorum and were highly resistant to TM and had a minimum inhibitory concentration higher than 1600 ppm. In inoculation tests in 2005, TM did not control disease after when wheat plants were inoculated with TM-resistant isolates of F. culmorum. This report is the first on the occurrence of benzimidazole resistance in F. culmorum.
A fruit stain symptom occurred on mature fruits of Japanese pear in Tottori Prefecture, Japan. Two kinds of yeastlike fungi were isolated from the surface of diseased fruits. The isolates were pathogenic to immature fruits of Japanese pear cv. Gold Nijisseiki, and reisolated from the inoculated fruits. Based on morphological and physiological characteristics and partial sequence analyses of rDNA, the isolates were identified as Meira geulakonigii and Pseudozyma aphidis. Because several kinds of filamentous and yeastlike fungi have already been recorded as the causes of fruit stain of Japanese pear, we propose these yeastlike fungi as new pathogens.
A new bacterial disease, causing water-soaked, blight and rot of leaves and stems, was observed on endive, Cichorium endivia L., in Okayama Prefecture in October 2002. The bacterium isolated at high frequency from affected petioles of endive was identified as Pseudomonas cichorii on the basis of bacteriological characteristics and the 16S rDNA sequence. Healthy seedlings were inoculated with the isolated bacterium, symptoms of the disease were reproduced, and the bacterium was reisolated from the lesions. The name "bacterial rot" was proposed for the disease.