檬果炭疽病之田間綜合防治

Abstract

在台南玉井數處中度發生炭疽病之愛文果園中，進行數項非農藥防治方法對檬果果實炭疽病防治效果之試驗。果園管理按一般農民常用之方法行之，果實採收後，經修剪、施肥、並定期施藥，果實於生理落果期停止後立即施藥套袋，至果實成熟期採果，經益收生長素3000倍稀釋液處理，等果皮轉色後，調查罹病果實率。使用方法中，以(1)套袋之防治效果最好，在採果後第12天時之發病率，幼果期即予以套袋之處理為0-5%，生理落果時套袋者27%，落果停止時套袋者42%，採果前兩星期者68%，無套袋者（全期施藥）72%。不同套裝材質不影響防治效果，但影響熟度、著色與糖度。早期套白色紙袋，可提高糖度，促進果實提早成熟5-7天，並防止果實日燒。(2)在一管理良好果園中，覆蓋黑色不織布之處理第9天發病率平均為6%，無覆蓋區為30%。(3)土壤施用有機質+石灰+硼酸三年後，可降低發病率約20-30%。(4)在花期與果實生育初期噴施從香蕉上分得之拮抗酵母菌、細菌、或放射菌，其防治炭疽病之效果與施農藥相仿，可以減少農藥施用量。由於在開花期如果不施藥，幼果時立即套袋，平均每個果實在採收後第9天亦有11-27個病斑。因此，現今田間病菌密度仍高時，非農藥防治方法雖能有效降低果實罹病率，且比農藥防治效果更佳，但由於花期無法套袋，故尚不能完全取代農藥防治，但可降低農藥使用次數達十次以上。 Pre-harvest control of mango anthracnose by mean of strategies other than pesticide control was also tested and evaluated in this study. During blossom period and fruit enlargement stage, trees were sprayed with pesticides every 7-10 days. At the end of physiological fruit drop period, mango fruits were sprayed with pesticides and then bagged at the same day or the next day. After bagging, trees were no longer sprayed or sprayed 1-2 times only until harvest. Fruits reaching 80-90% maturity were harvested, treated with Ethephon, and then the disease spots developed on fruits was recorded. The results showed as follows. (1) "Fruit-bagging" was found to be the most effective means for control of mango anthracnose disease. Fruits with anthracnose spots at the 12th day after ripening were 0-5% for bagging during fruit set period, and 27% and 42% for bagging during physiological fruit drop period and at the end of fruit drop period, respectively. The disease incidence for the bagging 2 weeks before mango fully mature was 68%. Whereas control (no-bagging but sprayed during whole fruit growing stage) was 72%. Different bagging materials or bagging paper treated with different oils did not affected the disease control effectively, but affected the maturation, color, and brix of mango fruit. White paper bags and bagging time earlier were better than other treatments. Fruits enveloped in white paper bags matured 5-7 days earlier, were with higher sugar contents, and without sun-burn injury. (2) Rhizosphere soil surface mulched with spun-bonded polyester was effective on control of anthracnose. The disease incidence was 6% for mulching treatment while 30% for controls at the 9th day after ripening. (3) Soil amended with boric acid plus lime plus organic manure for 3 years, anthracnose incidence decreased 20-30% comparing with the unamended treatment. (4) Spray of suspension of antagonistic yeast, or bacterium, isolated from banana fruits, every two weeks during blossom period was also effective for control of anthracnose and decreased the requirements of fungicides. Although fruit-bagging was the best means of disease control so far, without fungicide application during blossom period, 11-27 spots were still appeared on ripen mango even if fruits were bagged immediately after setting. Therefore, control of mango postharvest diseases with fungicides could be substituted partly, but not completely, by other methods today. Means including orchard sanitation, mulching, soil amendments, plus fruit-bagging could decrease more than 10 applications of fungicide sprays in the fields each year.