草坪草巨斑病及燒枯病之生物防治

Abstract

草坪生態系較一般農業顯著不同，其葉片密度甚高、常被低割造成傷口，加以高頻率灑水，故利於病害之發生及散佈。目前主要之病害防治方法為施用化學藥劑，不惟投入高成本，造成環境污染、且病原菌易產生抗藥性、危害有益生物，故近來已有學者開始進行生物防治之研究與應用。由Rhizoctonia solani所引起熱帶型草之巨斑病(large patch disease)或溫帶型草之褐斑病(brown patch disease)、及由Pythium spp.所引起之燒枯病(Pythium blight disease)，為草坪草最常見且嚴重之兩種病害。在國外已有應用哈茨木黴菌(Trichoderma harzianum) T1295-22菌株抑制溫帶型草(C3植物)病害成功之案例，惟目前尚乏熱帶型草(C4植物)病害之生物防治技術。故本研究旨在探討利用哈茨木黴菌及鏈黴放線菌(Streptomyces sp.)，抑制百慕達草(bermudagrass)、結縷草(zoysiagrass)、海雀稗草(seashore paspalum)等三種熱帶型草巨斑病及燒枯病之可行性。由培養皿菌落對峙培養實驗之結果顯示上述兩種生物防治菌對上列兩種病原菌皆具良好之拮抗能力。在溫室內以盆栽草苗接種病原菌及拮抗菌試驗之結果，發現木黴菌較放線菌對上述三種熱帶型草之兩種病害皆具較佳之抑制效果，且在延緩病害發展之成效十分顯著，即一般可延遲六天發病，以木黴菌生物防治之成效有些已等同於藥劑防治者，甚有超越者。本研究進一步在台大農場對現有草坪上之巨斑病施用木黴菌，另亦在農場新種植三種草坪草，並接種病原菌及施用拮抗菌，亦證實哈茨木黴菌於田間實際應用上具減低病害之能力。綜合上述研究結果，證明哈茨木黴菌對三種熱帶型草之巨斑病及燒枯病具有延緩病害發展及降低疾病嚴重度之成效。

Turf-ecosystem is very different from that of normal agriculture. Turf leaves, with high density, usually get wounded by cutting. The watering interval is very short for sport courts. These conditions faver the occurrence and dispersal of turf diseases. Among the turfgrass diseases, large patch(=brown patch) and Pythium blight, caused by Rhizoctonia solani and Pythium spp., respatively, are two major diseases around the world. The principal disease control method for turfgrasses is pesticide control, and it is associated with enviromental pollution, pesticide resistance, risk to beneficent organisms etc., in addition to the huge cost. Therefore, scientists have made great efforts in developing the biological control. There have been several successful examples of utilizing Trichoderma harzianum T1295-22 to suppress three diseases of temperate turfgrasses, which elong to C3 plants. However, there is still no biological contol method to control the diseases occuring on tropical turfgrasses, which belong to C4 plants. For this reason, this study is aimed for studying and developing the biological control methods for suppressing large patch and Pythium blight diseases of bermudagrass, zoysiagrass, and seashore paspalum by utilizing Trichoderma harzianum and Streptomyces sp. The dual culture experiments, with two biocontrol agents against two pathogens on PDA medium showed that both biocontrol agents are antagonistic to both two pathogens. Results of the pot experiments in the greenhouse, with both two biocontrol agents against both two pathogens showed that Trichoderma harzianum has better disease-suppression potential than Streptomyces sp. Application of the Trichoderma harzianum delayed the disease development for as long as 6 days, showing the same or even better disease-suppression efficacy than the fungicide azoxystrobin. Two field experiments were also conducted in the NTU Farm. The first was to apply the biocontrol agent in present turf to test the control efficacy of it. The second was to grow the new turfgrasses and apply the biocontrol agents simultaneously. In both experiments, Trichoderma harzianum exhibited good disease-control ability. In conclusion, Trichoderma harzianum is proven to have the potential to become a biocontrol agent to suppress the large patch and Pythium blight diseases of these three turfgrasses in Taiwan.