Annual Report of The Kansai Plant Protection Society Vol. 59(2017)

In order to clarify the thrips species composition on garden pea (snap pea), Pisum sativum ssp. hortense Asch., and broad bean, Vicia faba L., we investigated garden pea fields where different pesticides were sprayed at Kagoshima Prefectural Institute for Agricultural Development and from farmer’s pea fields (pea, 7 fields; broad bean, 5 fields) from Autumn to Winter. On garden pea, Thrips hawaiiensis (Morgan) and Frankliniella intonsa (Trybom) occurred, and T. hawaiiensis dominated throughout the investigation at both locations: Kagoshima Prefectural Institute for Agricultural Development and farmer’s fields. We considered that control by pesticides might not affect the thrips species composition. On broad bean, Thrips hawaiiensis (Morgan) also dominated; however, the proportion of F. intonsa on broad bean was higher (ca. 15 to 30% on average) than that of garden pea from October to November.

For the detection of Phytophthora nicotianae and Ph. capsici, a loop-mediated isothermal amplification (LAMP) assay was developed. The LAMP assay using species-specific primers could detect Ph. nicotianae and Ph. capsici within 60 min at 68°C as either extracted DNA, cultured mycelium, or crude sap from inoculated plants. The Multiplex assay using mixed primers and an isothermal DNA amplification and fluorescence detection device could detect Ph. nicotianae and Ph. capsici simultaneously.

Even if parsley is irradiated by UV-B to 60.0 μw/cm², its growth is not influenced. We controlled powdery mildew by irradiation at more than 9.0 μw/cm². However, when there are many sources of infection, UV-B cannot control it. We effectively restricted powdery mildew growth, by a combination of fatty acid glyceride emulsion and sodium bicarbonate·copper wettable powder applied for 3 weeks.

We developed methodologies for estimating the density of the larvae of tea spiny whitefly, Aleurocanthus camelliae Kanmiya and Kasai, in tea fields. In the period of rising density in 2013, 100 tea leaves were collected from each of 50 commercial tea fields in Shizuoka Prefecture, and the number of larvae and emerged exuviae of A. camelliae on the leaves was counted. Since a high correlation of R² = 0.98 or 0.99 was consistently found between the true larval density and apparent larval density, including emerged exuviae, from February–July 2013, the apparent larval density was used as a surrogate for true larval density in subsequent analyses. There was a significant correlation between larval density and the frequency of leaves infested by larvae, and this relationship was well described by the Kono and Sugino (1958) formula. Based on the resulting regression equation, we showed that the frequencies of leaves infested by the larvae corresponded to several steps of densities, assuming a standard value of the degree of occurrence of the pest. A significant positive correlation was found between mean density and mean crowding index in each field. The index of basic contagion α = 8.56 and the density-contagiousness coefficient β = 1.66 were obtained from the regression equation. Based on these values, the relationship between larval density and number of samples required to satisfy aimed precision D was simulated according to a study by Iwao and Kuno (1968). Results showed that, if the larval densities are 0.67, 0.33, and 0.16 or more per leaf, the aimed precision D = 0.3 for the survey is satisfied by sampling 50, 100, and 200 leaves, respectively.

We evaluated the susceptibility of Botrytis cinerea to fludioxonil by using 2,992 isolates from vegetables obtained from 2000 to 2016 in Mie Prefecture, Japan. Growth was not observed on potato dextrose agar that contained 0.2 ppm fludioxonil from 2000 to 2011. However, 27 of 971 isolates from 2012 grew under these conditions. Using these isolates, we performed a bioassay on cucumber cotyledons. Eight isolates showed less than 60% inhibition of lesion formation at 10% of the standard concentration. We defined these as low-susceptibility isolates.

In addition, when the susceptibility test was carried out using a microplate, the EC₅₀ value for the low-susceptibility isolates was between 0.188 and 0.271 ppm. This is an order of magnitude higher than the EC₅₀ values for susceptible isolates (0.012 to 0.063 ppm). Since the EC₅₀ value for the low-susceptibility isolates was 0.125 to 0.259 ppm higher than that of the susceptible isolates, the susceptibility of B. cinerea to fludioxonil can be evaluated using the microplate method.

The preventive effect on mating disruption of an artificial pheromone, fujikonyl butyrate, on the Japanese mealybug, Planococcus kraunhiae (Kuwana), was examined in persimmon fields. A low number of male adults were captured by a pheromone trap in the experimental plot where pheromone dispenser tubes were tied to persimmon tree branches. Most caged female adults located in the control (untreated) plot oviposited, whereas caged female adults in the treated plot with the pheromone did not oviposit. The numbers of larvae and adults detected on persimmon fruits in the treated plots were lower than the ones detected in the control plots. This trend did not depend on the number of dispenser tubes or points of tying. These results indicate that the application of 50–100 dispenser tubes per 1,000 m² in the persimmon fields effectively prevented the spread of Japanese mealybug by its mating disruption. This preventive effect was not dependent on field surroundings but might be insignificant in very small fields.

Predatory thrips, Haplothrips brevitubus (Karny), is an effective natural enemy for the control of pest thrips infesting strawberries in the greenhouse. To develop an IPM program using H. brevitubus, it is required to select pesticides which can be used with this predator based on the data from side-effect experiments conducted in the laboratory. In this study, we investigated the effects of three insecticides on H. brevitubus using strawberry plants in greenhouses. Although spraying these insecticides results in a high mortality of this species in laboratory experiments, we found that there were substantial individuals of this species on the plants after treatments of spinosad, spinetoram, or emamectin benzoate. Individuals of H. brevitubus, especially larvae who survived after spraying the pesticides, were seen in microspace refuges on strawberry flowers and young fruits. We consider that such microspace refuges on the strawberry plant might reduce the effect of the pesticide on H. brevitubus.

In March 2011, Eustoma (Eustoma grandiflorum) plants showing symptoms of a virus-like disease, such as leaf curling, yellowing, and abscised flowers, were found in Ise City, Mie Prefecture. Total DNA extracted from several leaf samples of symptomatic plants was subjected to diagnostic PCR analysis using primers specific to Tomato yellow leaf curl virus. All tested samples were positive for the Mld strain of TYLCV. We amplified the full-length viral genome DNA by rolling circle amplification followed by PCR, and the amplicons were cloned and sequenced. The complete genome sequence of all clones was 2,768 nucleotides in length and had 95% sequence identity with representative TYLCV isolates belonging to the Mld strain originating from tomato plants in Japan. By following the species demarcation criteria of ICTV, the isolate was defined as and grouped in the Mld strain. This is the first report of the complete nucleotide sequence of the Mld strain of TYLCV isolated from the Eustoma plant.

We conducted laboratory experiments to assess the disease control effects of pH-decreasing fertilizer as a new control material for lettuce big-vein disease. Results show that the occurrence of big-vein disease was suppressed in concomitance with the descent of soil pH by applying the fertilizer.

We investigated the effects of pH-decreasing fertilizer in laboratory experiments and in a field test. The occurrence of lettuce big-vein disease was prevented by decreasing the soil pH in the field test, similarly to the laboratory experiments, while causing no adverse growth effects on lettuce.

The preventive effect on leaf blast disease of probenazol and isotianil seedling treatments was high under a slight-occurrence condition of blast disease, including a QoI-resistant strain. Fipronil-probenazol, and isotianil showed high prevention values (over 85) until 58 days after planting under moderate- and heavy-occurrence conditions of blast disease, including a QoI-resistant strain.

We tested five fungicides (probenazole, iminoctadine albesilate, fludioxonil, tebuconazole, and boscalid) for the control of white rot (Sclerotium cepivorum) of Welsh onion (Allium fistulosum L.) planted in soil inoculated with the fungus. Two experiments in which each fungicide was applied twice showed that fludioxonil and boscalid gave excellent control.

Winter survival of tomato leaf mold fungus (Passalora fulva) was investigated in Hida City, Gifu Prefecture. Conidia placed on the field soil on December 13, 2012 died within a month, while those placed 1 m above the ground in the field and 3 m above the ground in the storehouse survived until the end of the experiment (May 14, 2013). This result suggests that conidia overwintering on agricultural materials become the primary inocula in the subsequent growing season.

We developed a simple method to test the quinone outside inhibitor (QoI) resistance of Pyricularia oryzae, which causes rice blast on Oryza sativa. After single spore isolation and incubation on potato dextrose agar (PDA) medium, 4-mm squares of fungal mycelia were picked and ground with 100 μl sterilized water. This suspension containing fungal mycelia (10 μl) was dropped on PDA medium containing 1, 10, or 100 ppm azoxystrobin. After 3–4 days incubation, sensitivity or resistance was determined by the presence or absence of mycelial growth. This method was easier and showed an accuracy similar to that of DNA analysis. We concluded that this method is useful for QoI sensitivity tests of rice blast fungus.

Tropidothorax sinensis (Reuter) (Hemiptera: Lygaeidae) was found on commercially cultivated eggplant in Kyoto City, Kyoto Prefecture, in late August 2016. T. sinensis adults and larvae damaged the growing point in eggplant. In this survey, eggplant was recorded as a new host plant of T. sinensis.

We surveyed the density of adults and larvae of Thrips hawaiiensis (Morgan) at 9 different developmental stages of flowers and pods of garden pea (snap pea), Pisum sativum L., in autumn (mid-November), winter (late-January), and spring (late-April) from 2015 to 2016, to elucidate suitable periods for quantitative pest censuses both for the adults and larvae. The density of both the adults and larvae differed largely and significantly among the developmental stages of the flowers and pods. The adult density was highest at the blooming stage, whereas the larval density was highest at the immature pod stage in autumn and spring and at the mature pod stage in winter.

Fruit damage caused by thrips has been a major problem in the cultivation of figs (Ficus carica L.). We examined the efficacy of using sorghum as a barrier crop in protecting fig fruits from this damage. The fruit injury rate of the barrier area was lower than that of the control area. Additionally, this resulted in an increase in the population of the natural enemies of thrips such as flower bugs and spiders.

The effects of a soil treatment of carbam sodium solution on the density of melon thrips, Thrips palmi Karny, was investigated after the harvesting of greenhouse cucumber. In the treatment plot, the cucumber was covered with a film, and the carbam sodium solution was sprayed on the soil surface. The number of adult thrips caught by blue sticky traps and emergence traps was lower in the treatment plot than in the film plot and the control plot. These results suggest that a soil treatment of carbam sodium can effectively control the density of thrips.

The toxicity of some insecticides to onion thrips (Thrips tabaci Lindeman) on Welsh onions in Kyoto Prefecture was evaluated at 25°C under a 15L-9D photoperiod. Among the 22 insecticides tested on female adults using the kidney bean leaf dipping method, benfuracarb MC, spinosad WP, spinetoram WP, tolfenpyrad EC, and pyridalyl WP were found to be highly effective. The toxic degree of other insecticides differed in each of the collected populations.

We used light-emitting diodes (LEDs) to examine the effect of red light on the behavioral responses of melon thrips, Flankliniella occidentalis. We allowed adults to choose between tomato plants exposed and unexposed to red LED light under ambient fluorescent lighting conditions. Thrips were less attracted to plants exposed to red LED light during 8- as well as 24-h exposure.

In order to gain knowledge of the migration of the smaller tea tortrix, Adoxophyes honmai Yasuda (Lepidoptera: Tortricidae), we compared the insecticide susceptibilities of two A. honmai strains. A conventional control strain and an organic farming strain were collected from two adjacent tea fields. Results showed that the two A. honmai strains indicated similar susceptibilities to the 13 insecticides tested, showing that the A. honmai moths migrated at a high frequency between the two adjacent tea fields.

A spirotetramat drench application in a nursery was compared with a systemic treatment of imidacloprid to evaluate the effects on spider mites, thrips, and Orius bugs on eggplants. The spirotetramat drench application exhibited high control effects for Tetranychus kanzawai and increased occurrences of Orius bugs in June because thrips were kept as a substitute prey of Orius bugs. The results show that spirotetramat drench application can decrease miticide spray and increase the occurrence of Orius bugs compared with imidacloprid systemic treatment.

A model to forecast the peak dates of adult emergence of the cotton bollworm, Helicoverpa armigera (Hübner), in Habikino City, Osaka Prefecture, was developed using a computer program provided by JPP-NET, which simulates seasonal changes in insect growth based on the total effective temperature. The model predicts that peak dates of H. armigera emergence in the city occur three to five days earlier as the annual air temperature rises by 0.5°C and that the number of H. armigera generations per year increases from four to five when the annual air temperature rises by at least 1.0°C compared to the average annual air temperature between 1981 and 2010.

We tested the suitability of Verbena ×hybrida ‘Tapian’ grown in planter cases (60 cm × 19 cm × 18 cm deep; 6 plants each) at maintaining Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae). Three months after the release of 50 adults per planter, each planter supported up to 750 adults and nymphs. The plant area stopped increasing at 1 m² per planter, and the aboveground biomass likewise stopped increasing at about 200 g. The N. tenuis population built up, even as the number of flowers decreased to zero.

The suppressive effect of predators wolf spider, Pardosa astrigera, on the population density of onion thrips, Thrips tabaci, on Welsh onion was investigated in laboratory tests. Test 1: Thirty adult females of T. tabaci and 20 nymphs of P. astrigera were released in 30 Welsh onion seedlings planted in pots. Two weeks after release, the number of T. tabaci and the damage on the Welsh onion were investigated. Our results showed that the number of T. tabaci and the damage caused by the release of P. astrigera were less than that of the no-release. Test 2: Thirty adult females of T. tabaci and five nymphs of P. astrigera were released in 3 Welsh onion seedlings planted in pots. In order to confirm the effect for a longer period, the number of T. tabaci and P. astrigera were investigated until 4 weeks after release, and as a result of releasing P. astrigera, the number of T. tabaci was less than the no-release on 16 to 28 days after release.

The toxicity of five insecticides on adult melon thrips, Thrips palmi Karny, was compared among three populations collected from cucumber greenhouses in Osaka Prefecture by using the common bean leaf dipping method. The corrected mortality rates associated with avamectin, spinosad, and spinetoram were low in a population sampled in Kanan Town in 2014.