Japanese pear scab caused by Venturia nashicola is one of the most prevalent diseases of Japanese pear trees in Japan. We estimated the sensitivity of this fungus to sterol demethylation inhibitor （DMI） fungicides on the basis of the disease severity in young pear trees pretreated with DMI fungicides and inoculated with fungal populations collected from commercial orchards in Fukuoka Prefecture in 2015. The protective values, 26.4-100.0 for
difenoconazole （active ingredient （a.i.）, 25 ppm）; 42.5-85.3, hexaconazole （a.i., 10 ppm）; 25.8- 44.2, fenbuconazole （a.i., 27.5 ppm）; and 30.6-49.9 fenarimol （a.i., 30 ppm）, were significantly reduced in comparison with those recorded in 2007（ P < 0.05, Welch test）. In an experimental
orchard in Fukuoka Prefecture, the efficacy of difenoconazole（ protective value, 87.6 in cultivar ‘Kousui’ and 74.7 in cultivar ‘Housui’） was higher than that of hexaconazole （protective value, 73.3 in‘ Kousui’ and 59.3 in‘ Housui’） in 2016. In a sensitivity test on young pear trees, the efficacies of difenoconozole （protective values, 85.9） and hexaconazole （protective values, 42.6） against fungal population from that orchard were similar to those in the orchard test. Therefore, the resistance of Venturia nashicola to DMI fungicides has a broad range in Fukuoka Prefecture.
Spatial pattern of citrus canker was examined in a lemon grove. Twenty-nine isolates of Xanthomonas citri subsp. citri were collected from the symptomatic leaves of lemon trees. All the citrus canker isolates caused corky lesion of citrus canker by pin-prick inoculation on navel orange leaves, confirming their pathogenicity. There was a correlation between the ability of mannitol utilization and the lesion area on navel orange. The physiological properties of bacteria demonstrated that all the isolates were classified into seven strains based on the utilization of carbohydrates （mannitol, mannose, maltose, lactose and malonate）. Strain 1 was the most prevalent type of strain among all the isolates and utilized all five kinds of carbohydrates, generating an aggregated distribution in a lemon grove. These results suggest that in the life cycle of citrus canker, young stem lesions of strain 1 from angular shoots would be potentially the dominant source for secondary infection.
We investigated prevalence of leafminer flies on okra cultivated in greenhouse in Ibusuki City, Kagoshima Prefecture, Japan. Liriomyza trifolii （Burgess） was the only leafminer pest found on okra. The numbers of leafminers in greenhouses where commercially produced parasitoid wasps, Neochrisocharis formosa （Westwood） were released at a density of 50 individuals/1,000m2, did not differ significantly from those in greenhouses where insecticides
were sprayed. These results suggested that biological control using parasitoids could be substituted for insecticides. However, as N. formosa which seemed to be derived from indigenous populations also occurred in greenhouses with insecticide applications, we considered that the effects of biological control in this study were obtained by the complex parasitoids populations including the indigenous ones. Since the indigenous parasitoids of leafminers have been known to be effective natural enemies, we also need to investigate the probability of conservation biological control on leafminers using indigenous parasitoids’populations for more developmental control strategies.
Thrips tabaci （Thysanoptera: Thripidae） is a major pest of asparagus in Saga Prefecture. We evaluated the effectiveness of Nesidiocoris tenuis（ Hemiptera: Miridae）, a biological control agent against T. tabaci, using banker plants in greenhouse asparagus. We examined effects of food （eggs of Ephestia kuehniella or fresh shoots of Sesamum indicum and Cleome hassleriana） in the nymphal stage of N. tenuis on the feeding amount of T. tabaci in the laboratory. The experiment revealed that nymphal food did not affect the number of T. tabaci fed on by N. tenuis. Then we prepared small greenhouses with four asparagus plants and released 50 individuals of T. tabaci and a pair of N. tenuis adults. The release of N. tenuis had a significant negative effect on T. tabaci density on asparagus, but T. tabaci population gradually increased from early August to late October. When either S. indicum, C. hassleriana, or Verbena × hybrida ‘Tapian’ was planted adjacent to asparagus as banker plants, N. tenuis kept the density of T. tabaci at low levels throughout the experiment. These suggest that the use of N. tenuis together with banker plants is effective to control T. tabaci populations in greenhouse asparagus.
The lethal effect of Decanoyloctanoylglycerol on eggs and larvae of Plutella xylostella L. was investigated. Decanoyloctanoylglycerol was found to be highly effective for population control in egg stage treatment. In a cabbage field, the mixing of Decanoyloctanoylglycerol with insecticides was suggested to increase the lethal effect. In the egg stage treatment of Saburina® containing Decanoyloctanoylglycerol: one of the products of Bacillus thuringiensis preparation, the effect was observed on the hatchling, and the mortality was 100% at 48 hours in the third instar larval stage treatment. In a cabbage field, Saburina® had a density suppressing effect compared with other BT, suggesting the possibility of it being used as one of the insecticides in the control program of P. xylostella.
The effect of mating disruption to the Japanese mealybug, Planococcus kraunhiae, for two cropping years on its population density and damage on fruits in Japanese persimmon orchards was examined. Mating dispensers (MD) containing 50 mg of 2-isopropylidene-5-methyl-4-hexen-1-yl butyrate, which is identified as a sex pheromone component of P. kraunhiae, were installed in two orchards in early April of each year at a density of 50-100 dispensers per 1,000 m2. In the first year, when population density of overwintering P. kraunhiae was high (2-4 individuals per twig), the MD treatment reduced the density of the second and third generations of P. kraunhiae with fewer chemical spray applications than control fields although damage on fruits was severer in MD-treated fields, probably because of high density of the first generation of P. kraunhiae in June in the MD-treated fields. In the second year, both densities of P.
kraunhiae population through the year and damage on fruits could be suppressed by the MD treatment. These results indicate that the two-year continuous MD treatment is effective for reducing damage on persimmon fruits in the second year by suppressing population density of P. kraunhiae.
Comstockaspis perniciosa is a pest that injures Japanese pear, citrus, and other economically important fruit trees. The addition of 1,000-fold diluted buprofezin to 150-fold diluted machine oil suppressed the density of the next generation of C. perniciosa. Additionally, buprofezin added to sodium dioctyl sulfosuccinate and polyoxyethylene alkyl ether showed a higher control effect on C. perniciosa than buprofezin alone or when added to machine oil. Generally, C. perniciosa is treated with pesticides during the hatching peak period at the end of May to effectively control outbreaks. If it is treated 2 weeks earlier, then buprofezin can suppress the density of hatchlings and a higher effect occurs with the addition of a paraffin-spreading agent.
The effects of chrysanthemum illuminated by a red light-emitting diode bulb which has been developed for regulation of chrysanthemum flowering on the population density of Thrips nigropilosus was investigated twice in a greenhouse. Experiment 1 was started at more than three months after planting chrysanthemum（ high density of the thrips） and experiment 2 was started just after planting （low density of the thrips）. As a result, both experiments showed that the density of the thrips on plants under red LED illumination for 24 hours was significantly lower than those under incandescent lamp which is commonly used in that area. Besides, experiment 2 showed that the density of the thrips under red LED illumination for 24 hours was significantly lower than those for three hours. Our study is the first report to show that using red LED is effective for suppressing the density of T. nigropilosus on cultivating
chrysanthemum to some extent. Therefore, illumination with red LED has the possibility to be an effective and economically efficient measure for control of the thrips on chrysanthemum in combination with other measures such as insecticide applications because the red LED requires one tenth the electricity consumption of the commonly used light.
Suppressive effects of root-knot nematode-suppressive black oat ‘KH1a’ on root-lesion nematodes, Pratylenchus penetrans and P. coffeae, were examined in inoculation and field tests. Results of inoculation tests indicated that ‘KH1a’ was as poor a host for P. penetrans as black oat ‘Hay oats’, which is a common P. penetrans-suppressive green manure crop in Japan. In field tests, ‘KH1a’ reduced soil P. penetrans density significantly lower than bare fallow and the
effect was not different from those of ‘Hay oats’ or ‘Saia’. These results indicated that ‘KH1a’ can be used as a P. penetrans-suppressive crop like ‘Hay oats’ and ‘Saia’. Although ‘KH1a’ and ‘Hay oats’ were poor hosts also for P. coffeae in inoculation tests, field nematode densities after cultivation of these black oats were not significantly different from that after bare fallow, indicating that the suppressive effects of these black oats on P. coffeae were not comparable to those on P. penetrans.
Fauna of lepidopteran, coleopteran and orthopteran insects feeding on wild soybean, Glycine soja Sieb. et Zucc., and abundance of respective species in vegetations including wild soybean were investigated in Kumamoto City and its environs (Kumamoto, Kashima, Ozu, Koshi and Shisui) from 2011 to 2015. Lepidopteran insects, Paragabara ochreipennis, Omiodes miserus, O. indicatus, Matsumuraeses falca, and Pleuroptya ruralis were found in abundance at many surveyed vegetations. Coleopteran insects, Medythia nigrobilineata and Popillia japonica, as well as orthopteran insects Patanga japonica and Oecamthus euryelytra were found in abundance at only some surveyed vegetations. Many coleopteran and orthopteran insects were found in Kashima, whereas few in Shisui. It seems that the difference in abundance of each species among the surveyed vegetations could be caused by the presence and amount of host plants in the field habitat including the surrounding environment.