桃流膠病藥劑防治之研究

Abstract

桃樹(Prunus persica (L.) Batsch)原產於中國，現已於世界各地種植，在台灣主要種植於台中、桃園、新竹及南投。栽培生產主要分成低海拔硬肉桃、低海拔水蜜桃及高海拔水蜜桃三種生產類型。近年，為減緩高山墾殖對環境造成之壓力，桃樹低海拔化之種植技術已獲得支持。其中，「台農甜蜜」為平地水蜜桃主要栽培品種之一，因此本研究即以「台農甜蜜」為盆苗測試品種。桃樹常見病蟲害有桃蚜蟲、穿孔病、縮葉病、流膠病等。桃流膠病為桃樹嚴重病害之ㄧ，感染流膠病據統計可導致40%之桃產量減產。本研究觀察台中及台北二果園，發現流膠病在生長環境不良、傷口多及生長勢弱之果園發生較為嚴重。從此二果園桃樹之凹陷病斑、疣狀凸起及流膠中，以組織塊分離或稀釋分離，皆可分離到流膠病菌。經由菌絲塊傷口接種及孢子懸浮液傷口接種，皆能造成健康株之發病，並可再分離到流膠病菌，完成病原性測定及柯霍氏法則之驗證。桃樹於苗期感染桃流膠病將影響生長高度。自台中、台北二地分離篩選出之二株桃流膠病分離株，菌絲最適合生長溫度為25oC，經形態鑑定及分子檢測後發現台中分離株為葡萄座腔菌Botryosphaeria dothidea而台北分離株可能為Diplodia seriata、Sphaeropsis sapinea或Botryosphaeria obtusa，兩者在分生孢子形態及DNA序列上皆顯著不同，證實台北及台中兩地之桃流膠病菌為兩種不同之真菌。本研究並從國內外報告，篩選對上述二病原菌有防治效力之藥劑進行化學防治測試。其中免賴得(Benomyl)、貝芬替(Carbendazim)、待克利(Difenoconazole)、撲克拉(Prochloraz)、撲滅寧(Procymidone)、普克利(Propiconazole)、得克利(Tebuconazole)、甲基多保淨(Thiophanate-methyl)經測試對抑制流膠病菌菌絲生長有較佳的效果；而免賴得、貝芬替、待克利、撲克拉、撲滅寧、普克利、得克利對分生孢子發芽有較佳效果。於盆苗試驗中，發現噴施亞托敏(Azoxystrobin)、貝芬替及撲克拉之防治效果良好。在田間試驗中，則以噴施亞托敏、撲克拉防治效果良好；而在注射藥劑方面則以待克利及得克利效果較佳。在台灣目前桃流膠病發病已十分嚴重，但迄今尚無公告的推薦防治用藥，本研究因此希望透過病原菌之發生生態、生理特性以及病害好發環境等，同時篩選測試有效之防治藥劑，改進施藥方式及技術，期望可以提高流膠病的防治成效。

Peach (Prunus persica (L.) Batsch) is native in China, planted worldwide now. In Taiwan, peaches are mainly planted in Taichung, Taoyuan, Hsinchu and Nantou. Production is divided into three types: Low altitude crisp peaches, low altitude and high altitude juicy peaches. In recent years, for mitigating the pressure from alpine reclamation, agricultural scientists developed the technology for planting peaches in low altitude or plain area. “Premier” is one of the most important cultivar of the low altitude juicy peaches. Thus we choose this cultivar for this study. Aphids, bacterial leaf spot, leaf curl and gummosis are major diseases of peach. Peach gummosis is one of the most destructive diseases. According to the statistics, peaches will lose more than 40% yield if infected with this disease. After investigation in oneTaichung and one Taipei orchard, we found that gummosis occurs seriously in poor-managed orchards, with a lot of wounds and weak growth. This study isolated the pathogens of peach gummosis from stem lesions, blisters and gums in these two orchards by tissue block isolation method and dilution isolation method. The healthy peach stems showed gummosis after inoculating by mycelium discs and spore suspensions at wounds.The infected seedlings showed reduced tree height and wrose health. And we could reisolate the pathogens from diseased peach stem for fulfilling the Koch’s postulates. This study identified 2 different peach gummosis isolates from Taichung and Taipei, respectively. The best mycelial growth temperature of these two isolates is about 25o. The isolate from Taichung is identified as Botryosphaeria dothidea, while the isolate from Taipei preliminarily identified as Diplodia seriata, Sphaeropsis sapinea or Botryosphaeria obtusa. The different conidia morphology and DNA sequence show that the two isolates are different pathogens. By testing some fungicides reported in recent paper for chemical control, we showed that benomyl, carbendazim, difenoconazole, prochloraz, procymidone, propiconazole, tebuconazole, and thiophanate-methyl were able to inhibit the mycelial growth of peach gummosis isolates; while benomyl, carbendazim, difenoconazole, prochloraz, procymidone, propic-onazole and tebuconazole were able to inhibit the conidia germination of the pathogen. In pot test, azoxystrobin, carbendazim and prochloraz had shown good control effect. In field test, spraying azoxystrobin and prochloraz on stem exhibited good control effect. With big peach trees in orchard, we inject the fungiciedes in the basal stem. Results showed that difenoconazole and tebuconazole can reduced the gummosis. There is no formal chemical control fungiciedes recommended for controlling the peach gummosis in Taiwan. Therefore, this research is aimed to screen some adequate fungiciedes and develop better applying techniques for controling this serious disease.