Gray mold and leaf blight of komatsuna (Brassica campestris L., rapifera group) and German violet (Exacum affine Balf.) occurred in Tokyo Metropolis in 2006. The fungi isolated from the infected plants with gray mold were identified as Botrytis cinerea Persoon: Fries. Inoculation tests showed that these fungi were causal agents of the diseases. This is the first report of gray mold on these plants in Japan.
Anthracnose of rocket salad (Eruca vesicaria subsp. sativa (Mill) Thell.) occurred in Tokyo Metropolis in 2004. The causal fungi isolated from the diseased plants were identified as Colletotrichum higginsianum Saccardo. Inoculation tests showed that these fungi were the causal agents of the disease. This is the first report on the disease in Japan.
Two predatory bugs, Piocoris varius (Uhler) and Geocoris proteus Distant, were evaluated for control of the two-spotted spider mite Tetranychus urticae Koch on strawberry and the cotton aphid Aphis gossypii Glover on watermelon under greenhouse conditions. Third instar nymphs of either of the two predators were released three times to each greenhouse. The release of P. varius suppressed the population densities of both mite and aphid to a lower level than the control greenhouses. P. varius persisted on the plants throughout the research periods. By contrast, the release of G. proteus suppressed the mite density in the strawberry greenhouse over a short period, but had no effect on the aphid density in the watermelon greenhouse. The instability of pest control efficacy of G. proteus may be caused by their micro-habitat selection since they were frequently observed on the ground rather than plants. These results suggest that P. varius is more suitable for the release than G. proteus.
We tested the effectiveness of releasing big-eyed bug Piocoris varius (Uhler) for control of two flower thrips, Frankliniella intonsa (Trybom) and F. occidentalis (Pergande), in sweet pepper greenhouses. Second instar nymphs of P. varius were released three times at the rate of 5 nymphs per plant per release. The release of P. varius suppressed the thrips density to low levels for 2 months, while the conventional chemical control was unsuccessful. The effectiveness of P. varius was not influenced by several applications of fungicides. P. varius nymphs were constantly found on the plant throughout the experiments and adults emerged 2 months after the release. Our result suggests that P. varius is a promising biological control agent of the flower thrips.
Distribution of the alfalfa weevil, Hypera postica (Gyllenhal)(Coleoptera: Curculionidae) was surveyed at 179 sites of 16 prefectures in Central and Northern Honshu Island, Japan in the spring of 2006. H. postica was recorded for the first time in Toyama, Ishikawa, Fukui, Yamanashi, and Nagano Prefectures, but could not be found in Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima, and Niigata Prefectures. In Ibaraki and Tochigi Prefectures, H. postica extended its distribution range about 60km northward from the spring of 2003 to the spring of 2006. H. postica was distributed widely in the plains of Saitama and Gunma Prefectures where the weevil has already been found.