Takeshi Kanto

Strawberry powdery mildew caused by Podosphaera aphanis , one of the most important diseases affecting strawberry production in Japan, can be effectively controlled by supplemental ultraviolet (UV) irradiation. Here, we investigated disease severity on plants irradiated with UV light at 270–380 nm with/without inoculation and demonstrated significant decreases in disease severity on the UV‐treated plants throughout almost all of the experiment periods. Daily UV irradiation for 3 hr (0.17–0.96 kJ ⋅m ⁻² ⋅day ⁻¹ ) significantly reduced the incidence of powdery mildew on UV‐treated strawberry at day 58 after initiation of UV irradiation in a natural infection and at day 168 in artificial inoculation tests compared with non‐UV‐treated controls. Furthermore, we found that two pathogenesis‐related protein (PR) genes were up‐regulated 7 days after initiation of UV irradiation on plants before or after transplantation into raised beds. Transcript levels of five defence‐response genes were estimated using quantitative reverse transcription PCR to determine whether UV irradiation induced a defence response; PR ‐ 3 and PR ‐ 5 transcripts were significantly higher in the UV‐treated strawberry leaves after UV irradiation than in the non‐irradiated controls. In addition, transcript levels of both genes were significantly up‐regulated in plants irradiated with a higher radiant dose (0.90–0.96 kJ ⋅m ⁻² ⋅day ⁻¹ ) within 7 days after initiation of UV treatment, compared with plants exposed to a lower dose (0.17 kJ ⋅m ⁻² ⋅day ⁻¹ ) and with controls. Thus, PR ‐ 3 and PR ‐ 5 are induced in strawberry leaves as part of a defence response that is induced by UV irradiation.

ISHS V International Symposium on Tomato Diseases: Perspectives and Future Directions in Tomato Protection Ultraviolet B radiation from a compact fluorescent lamp for tomato disease control

Development of spider mite management technology other than chemical control is desired because of the serious development of acaricide resistance worldwide. Recent studies have evidenced the lethal effects of ultraviolet-B (UVB) radiation on spider mites. To develop the technology on how to use UVB irradiation for spider mite control, we tested whether UVB lamp–light reflection sheet (LRS) combinations suppressed the population size of Tetranychus urticae Koch on strawberry in a greenhouse from December to May (2012–2013, 2013–2014) in Japan. We designed four combinations of UVB lamps and LRSs: 1) neither UVB lamps nor LRSs (UV−LRS−); 2) a UVB lamp without an LRS (UV+LRS−; 2012–2013 only); 3) a UVB lamp and a mulch-type LRS (UV+LRSm); and 4) a UVB lamp and a wing-type LRS (UV+LRSw). The number of adult females peaked at 438.0 and 222.0 per plant in UV−LRS− of 2012–2013 and 2013–2014, respectively, and peaked at 191.6 females in UV+LRS− of 2012–2013. In contrast, the peak abundance was 20.9–98.0 females in UV+LRSm, and fewer than 15 females were noted in UV+LRSw over either experimental period. UVB irradiance on lower leaf surfaces was higher in UV+LRSm and UV+LRSw than UV−LRS− and UV+LRS−, and the mite densities were significantly correlated with UVB irradiance on lower leaf surfaces. Consequently, we conclude that the combinations of UVB lamp–LRS have an excellent capacity to control T. urticae on greenhouse strawberry, and that the LRS was an essential component in this technological approach.

ISHS VII International Strawberry Symposium A NEW UV-B LIGHTING SYSTEM CONTROLS POWDERY MILDEW OF STRAWBERRY

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ISHS VI International Strawberry Symposium UV-B RADIATION FOR CONTROL OF STRAWBERRY POWDERY MILDEW