We investigated the survival period of Colletotrichum gloeosporioides on anthracnosediseased withered mango leaves under varying temperature conditions. Conidial masses on the diseased withered leaves survived for 120, 150, 210, and more than 300 days at the temperature conditions of 35 °C, 25 °C, 15 °C, and 10 °C, respectively. A strain was isolated from a diseased withered leaf of each temperature condition, and all four isolates were confirmed to cause disease on fruit. In summary, C. gloeosporioides was able to survive for long periods on diseased withered leaves, with survival period increasing with decreasing temperature. Furthermore, the long survival period did not reduce pathogenicity. These results suggest that diseased withered leaves and debris in the field may serve as an infection source for mango anthracnose.
Blast pathogens of three Setaria plants（ foxtail millet, green foxtail and giant foxtail） are classified into Pyricularia oryzae Setaria pathotype based on their specific virulence to foxtail millet among differential Gramineae species. Pathogenicity of 44 P. oryzae isolates from the three Setaria plants were tested on five accessions of green foxtail and three accessions of giant foxtail. All of the isolates tested produced susceptible reactions on more than three accessions of green foxtail and more than one accession of giant foxtail, indicating that they were pathogenic to green and giant foxtails as well as to foxtail millet. In the present study, differential patterns of avirulence on accessions of green foxtail and giant foxtail were observed among the green foxtail isolates and among the giant foxtail isolates.
Fifteen Pyricularia oryzae isolates from giant foxtail（Setaria faberii） were collected from a wide geographic range in Japan and subjected to DNA fingerprint analyses using transposable elements MGR586 and MAGGY as probes. The DNA fingerprint analyses revealed a complex lineage structure of the 15 isolates. When lineages were arbitrary defined as a group in which members shared greater than 70% similarities in their DNA fingerprint profiles, the 15 isolates could be sorted into 12 and 15 lineages by MGR586- and MAGGY-DNA fingerprint analyses, respectively. Three microgeographic populations of the giant foxtail pathogen, each of which contained 15 isolates collected from a １㎡ area, were subjected to MGR586-DNA fingerprint analysis. In one of the three populations, the 15 isolates were sorted into two lineages with around 70% similarity. In contrast, all of the 15 isolates in the other two populations formed a single lineage with greater than 70% similarities. The giant foxtail pathogen was considered to possess a complex lineage structure, even at the microgeographic scale. However, the simple lineage structure observed in the two populations suggests that the complexity of lineage structure of the pathogen at the microgeographic scale varies depending on collection sites.
Effectiveness of conservation biological control against the cotton aphid Aphis gossypii Glover was evaluated in okra Abelmoschusesculentus（L.） Moench. fields at Ibusuki, Kagoshima from May to September in 2014. In a field where broad-spectrum insecticides had been applied frequently, natural enemies did not occur and A. gossypii populations increased rapidly in September. On the other hand, in a field where indigenous natural enemies were conserved and enhanced with selective insecticides and insectary plants （barley and sorghum）, natural enemies such as aphid parasitoids, ladybird beetles, hoverflies, predatory gall midges, lacewings, and flower bug, occurred and cotton aphids remained at low density, indicating that conservation biological control can be effective against A. gossypii on okra.
We examined host stage preference of Allotropa subclavata, the most effective natural enemy of Planococcus kraunhiae, one of the serious fruit pests in Japan. Though adult females of A. subclavata drummed on all stages of the host, wasps could effectively insert the ovipositor against first and second instar nymphs. The next generation adults emerged from the hosts only when the wasps parasitized their first and second instar nymphs.
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