In 1992, basal petiole rot and root rot of edible burdock were found in three fields in Hokkaido, Japan. Three isolates were obtained from each field. Two and one isolate were identified as Rhizoctonia solani anastomosis group (AG)-2-2 IIIB and AG-2-2 IV, respectively, based on hyphal anastomosis reaction, culture appearance, temperature-dependent growth characteristics, and specific PCR. The originally observed symptoms were reproduced on roots inoculated with the isolates. Edible burdock black scurf caused by R. solani AG-2-2 IIIB has been previously reported in Japan, however, there are no reports of AG-2-2 IV. Therefore, we propose to include it as one of the pathogens of the disease.

Bunt disease of wheat caused by Tilletia controversa poses a serious problem in Hokkaido. The pathogen survives in the soil as teliospores, which serve as a source of infection for several years. This study aimed to develop a method for the quantitative detection of T. controversa from infected soil using real-time PCR with a TaqMan probe. The detection limit of this method was 10 spores/g soil. The number of DNA copies increased as disease severity increased. This method facilitated the quantification of T. controversa inoculum from the infected fields. Thus, disease occurrence may be predicted by testing the soil before sowing.

Pyribencarb is a fungicide used to control the apple scab disease in Hokkaido. It functions as a quinone outside inhibitor (QoI). QoI-resistant strains of Venturia inaequalis, carrying the G143A mutation, have recently been identified in Hokkaido. This mutation affects mitochondrial cytochrome b in V. inaequalis. The sensitivities of the V. inaequalis isolates collected from Hokkaido to pyribencarb and trifloxystrobin were compared. Isolates carrying the G143A mutation exhibited reduced growth on a medium containing pyribencarb than on that containing trifloxystrobin.

The leaves of strawberry seedlings were sprayed with a conidial suspension of Podosphaera aphanis var. aphanis within one week of their complete unfolding. In all four strawberry cultivars tested, lesions first developed on the 5th day post-inoculation, and new lesions, which were originated from inoculated conidia, appeared continuously until the 9th day post-inoculation, possibly for a few more days. The number of lesions that appeared on the 5th day was <5% of the total lesions developed during the 13-day post-inoculation period in the three cultivars, “Mo-ikko,” “Nyoho,” and “Saga-honoka.” In the cultivar “Sanuki-hime,” 14.6% of the total lesions appeared on the 5th day post-inoculation, while the number of lesions that developed each day between the 9th and 13th days was <11% of the total. Thus, depending on the cultivar, more lesions developed over two to three days between the 5th and 8th days post-inoculation. Considerably greater levels of infection occurred at a relative humidity of 100% than at 50% (p < 0.05). Twenty-four or forty-eight hours of leaf wetness post-inoculation with a conidial suspension neither significantly reduced nor increased the infection levels in the seedlings of “Mo-ikko” and “Nyoho” cultivars (p < 0.05).

This study investigates the species composition and seasonal presence of hoverflies (Diptera: Syrphinae), which larvae are arthropod predators, across three sites in each of three Tohoku region prefectures (Aomori, Iwate, and Miyagi), Japan. The number of adult hoverflies captured using blue sticky traps, which was placed on buckwheat flower plots, was quantified per species between 2021 and 2022. Although species diversity and composition exhibited variation among years and prefectures, the prevailing taxa in all regions were Sphaerophoria macrogaster, Eupeodes corollae, and Melanostoma spp. Notably, S. macrogaster consistently exhibited higher capture rates, suggesting its potential for biological control in the Tohoku region. Total hoverfly captures decreased in August during periods of elevated temperatures in both years. To ensure hoverfly utilization throughout the summer, it is important to identify factors contributing to this decline under high-temperature conditions and establish an environment that mitigates these effects.

Over two years, the suitability of the hoverfly Eupeodes corollae as a pollinator in strawberry greenhouses was investigated. These experiments involved comparing plots with and without the release of E. corollae in 63.2 m² areas. In the 2022 experiment, where a total of 113 adults were released 5 times between December 19 and March 19 at intervals of 13–30 days, a 26.3% increase in the rate of normally pollinated fruit was observed compared with nonrelease plots. In the 2023 experiment, involving a total of 50 adults released 5 times between December 12 and January 29 at intervals of 10–13 days, a 48.2% increase in the rate of normally pollinated fruit was observed until March 10. This period coincided with E. corollae adults contributing to pollen dispersal. These results indicate the feasibility of using E. corollae as strawberry pollinators in greenhouses.

The residual efficacy of diamide insecticides against summer fruit tortrix larvae, Adoxophyes orana fa­sciata, was evaluated by collecting apple tree leaves at 7, 16, and 37 days after spraying, and rearing larvae on these field-aged leaves. At 7 days after spraying, diamide insecticides exhibited robust efficacy, with larval mortality of 92%–100% across all treatments. At 16 days after spraying, the efficacy varied among insecticides: flubendiamide achieved 96% mortality, tetraniliprole and chlorantraniliprole reached 87%, cyclaniliprole resulted in 57%, and cyantraniliprole achieved 16%. Flubendiamide maintained a high larval mortality rate of 92% even after 37 days. No diamide insecticide was effective when larvae were reared on leaves from terminal shoots that emerged after spraying and were collected at 16 days after spraying. The residual efficacy of diamide insecticides in the field appears to depend on the differential potency of these insecticides and the seasonal variations in apple tree shoot development.

In orchards, the density of specialist phytoseiid mites, including Neoseiulus womersleyi, typically increases only after spider mite numbers reach damaging levels. To effectively employ them for Tetranychus urticae control, overcoming this time delay is imperative. Spiracle-blocking insecticides, which are benign to phytoseiid mites, hold promise as compounds that can be combined with N. womersleyi to rapidly suppress T. urticae. In 2020 and 2021, we conducted a comparative study between two apple orchards: orchard A, where propylene glycol monolaurate was applied 2–3 times upon the initial appearance of N. womersleyi, and orchard B, where the compound remained unsprayed. The results revealed significantly shorter periods until T. urticae suppression in orchard A compared with orchard B in both years. Moreover, the total counts of T. urticae occurrences in orchard A were significantly lower than those in orchard B for both years.