Intercropping with Welsh onion and Chinese chive was evaluated as a means to reduce the incidence of Fusarium wilt on spring-summer spinach caused by Fusarium oxysporum f. sp. spinaciae (FOS). In preliminary experiments (i.e., plant box experiment and container experiment), intercropping spinach with Welsh onion and Chinese chive suppressed development of spinach Fusarium wilt. Particularly, intercropping with Welsh onion yielded stronger suppression. Subsequently, at two commercial spinach fields in Takayama City, Gifu Prefecture, during the first cultivation season after soil fumigation, Welsh onion and Chinese chive were intercropped on the ridge shoulders along the sides of rain shelters where FOS often survives. As a result, both intercropping systems effectively reduced the incidence of spinach Fusarium wilt (44 to 100% reduction) up to 5 months post fumigation. F. oxysporum was detected from soils in the ridges of plots with spinach-Chinese chive intercropped at a level similar to that in plots with only spinach, and soil populations of F. oxysporum in spinach-Welsh onion intercropped plots were undetectable during cultivation. These results suggest that intercropping with alliums, particularly Welsh onion, on ridge shoulders along the sides of rain shelter after soil fumigation can effectively reduce the incidence of Fusarium wilt on spring-summer spinach.

The control of bacterial fruit blotch, caused by Acidovorax citrulli (Aac), a seed-borne pathogen of cucurbits, is important to prevent expansion of the pathogen into new areas in Japan. To establish a more effective hot water treatment to disinfest seeds, we examined effects of treatment temperature, treatment duration and temperature changes on the survival of Aac. To kill off Aac in a short time, intermittent heat treatments of repeated heating (50°C) and cooling (20°C) in turn was more effective than continuous heat without cooling. Because dry heat is not easily transmitted through the large seeds, which also harbor numerous bacteria, the effect of intermittent hot water treatment using hot water and cold water in a small regulated water bath was tested on artificially infested seeds of wet squash. The intermittent hot water treatment was more effective than the continuous hot water treatment for 20- and 30-min durations. The test using a bacterial suspension yielded nearly the same results. Further combining the intermittent hot water treatment with 0.01 M acetic acid and a mixture of 0.168% basic copper chloride prevented infection by Aac. Large amounts of squash seeds can thus be treated in a large regulated water bath to disinfest seeds as effectively as treating small amounts of seed in the small water bath. The optimum condition was a 30-min intermittent hot water treatment (53°C) with 0.01 M acetic acid and a mixture of 0.168% basic copper chloride. Although germination vigor and germination rate of the seeds tended to decrease slightly after the intermittent hot water treatment, germination rate was around 60% and was not in a problem for seed stock.

Since 2012, a severe postharvest rot of mango fruits (cv. Lippens) has been found in Okinawa Prefecture, Japan. A fungus frequently isolated from the diseased fruits was identified as Neofusicoccum parvum based on morphological, cultural characteristics and sequence similarity of rDNA-ITS region and EF1-α gene. The isolates reproduced the symptoms on mango fruits after inoculation and were reisolated from the inoculated fruits. Neofusicoccum parvum is proposed as another pathogen of stem-end rot of mango in Japan.