亞磷酸及藻類資材防治甘藍黃葉病之可行性評估

Abstract

甘藍(Brassica oleracea L. var. capitata)為臺灣栽培面積和產量最大的葉菜類。夏季好發由Fusarium oxysporum f. sp. conglutinans (Foc)引起之甘藍黃葉病(Fusarium wilt)，然而除了抗病品種外，無有效防治手段，但臺灣目前可用之抗病品種相對有限。前人研究中亞磷酸(phosphite)具田間防治潛力，但使用上有其限制。因此本研究旨在嘗試不同亞磷酸施用方式，並且於自然罹病田驗證其效果，發展一套能實際於田間應用之防治策略，同時篩選具防治潛力之藻類資材，以尋求多種防治資材，避免單一資材可能之副作用。亞磷酸葉面施用試驗中，葉面施用不具防治效果，仍得澆灌於介質或土壤中以直接抑制Foc。初步評估亞磷酸於戶外人工接種苗圃之防治效果，結果顯示，500倍稀釋間隔澆灌無法降低‘228’之罹病度，同時產量也下降；此外也觀察到，‘夏強60’於亞磷酸處理下產量增加，而‘266’則下降，推測亞磷酸是否具備正面效果或許也和品種特性有關。自然罹病田試驗中，嘗試100倍、500倍和1000倍稀釋配合間隔或連續施用亞磷酸，及不同農膜以降低土溫，然而施用亞磷酸無法降低黃葉病發生情形，推測與土壤微生物相、亞磷酸副作用等因素有關，但泰維克布之罹病度顯著低於銀黑塑膠布。藻類資材的篩選結果顯示，澆灌各項資材均不能顯著降低‘228’之罹病度和罹病率，部分處理甚至提高罹病度，僅兩款市售藻類液態有機質肥料能些微降低罹病度，但統計上未達顯著差異；而在濃度試驗中，市售藻類液態有機質肥料在高濃度下可能加劇罹病度，推測主要是不斷將有機質施入介質中促使病原菌生長而導致無效。總而言之，亞磷酸應用上需要維持特定濃度，既不影響土壤微生物且能抑制Foc，而藻類資材或是有機資材不應冒然使用，但是單一資材有其侷限，未來仍待配合不同資材或栽培手段以達穩定之防治效果。

Cabbage (Brassica oleracea L. var. capitata) is the leafy vegetable with the largest cultivation area and highest production in Taiwan. Cabbage Fusarium wilt, caused by Fusarium oxysporum f. sp. conglutinans (Foc), is highly prevalent during the summer. However, apart from utilizing resistant cultivars, there are currently no effective control methods, and the number of resistant cultivars available in Taiwan is relatively limited. Previous studies have indicated that phosphite possesses potential for field disease control, though its application has limitations. Therefore, this study aimed to test various phosphite application methods and verify their efficacy in naturally infested fields to develop a practical field control strategy, while simultaneously screening algae materials with disease control potential to identify diverse alternative agents and avoid the potential side effects of relying on a single material. In the foliar application experiment, foliar application of phosphite showed no control efficacy; it was still necessary to irrigate the growing medium or soil to directly inhibit Foc. In the artificially inoculated outdoor nursery trial evaluating the preliminary efficacy of phosphite, results showed that interval irrigation with a 500-fold dilution failed to reduce the disease severity of ‘228’, and the yield also decreased. Furthermore, it was observed that the yield of ‘Xia Qiang 60’ increased under phosphite treatment, whereas that of ‘266’ decreased, suggesting that whether phosphite exerts positive effects may be related to specific cultivar characteristics. In naturally infested field experiments, phosphite was applied at 100-fold, 500-fold, and 1000-fold dilutions at intervals or continuously, combined with different agricultural mulches to lower soil temperatures. However, application of phosphite did not reduce the occurrence of disease, which is speculated to be related to factors such as soil microbial community and the side effects of phosphite. Nevertheless, the disease severity under Tyvek mulch was significantly lower than that under silver-black mulch. The screening of algae materials revealed that irrigating with various materials failed to significantly reduce the disease severity or disease incidence of ‘228’, with some treatments even increasing disease severity. Only two commercial liquid algae-based organic fertilizers showed a slight reduction in disease severity, but the difference was not statistically significant. Furthermore, the concentration experiment indicated that high concentrations of these commercial liquid algae-based organic fertilizers could worsen disease severity, likely because continuously introducing organic matter into the growing medium promoted pathogen growth, ultimately rendering the treatment ineffective. In conclusion, the application of phosphite requires maintaining a specific concentration that can inhibit Foc without disrupting soil microorganisms. Additionally, algae or organic materials should not be used rashly. Given the inherent limitations of any single material, combining different materials or cultivation practices remains essential to achieve stable disease control efficacy in the future.