本研究主要針對鐵鉀砷酸銨(MAFA)及克枯爛(tecloftalam)，於水稻不同生育期施用對產量及產量成份之影響，同時以胡瓜、萵苣及水稻三種測試作物之胚根伸長反應，檢測臺灣水田常用農藥引起作物藥害之潛力，做為農藥安全使用的參考和依據。於水稻幼穗分化期、孕穗期及抽穗始期，噴施2000倍之6.5%鐵鉀砷酸銨溶液，會引起會稻穗扭曲、雌蕊柱頭乾枯之異常現象；幼穗分化期處理導致穗長、單穗重、每穗粒數、稔實率及千粒重均達20%以上之抑制，其中千粒重高達35%。噴施1000倍之10%克枯爛可濕性粉劑，稻株發生鞘葉自葉尖及葉緣向葉基及中肋部分黃化，穀粒內外穎褐化、空穗等異常；對稻穗生長之影響程度亦以幼穗分化期最為明顯，千粒重減少達25%左右。鐵鉀砷酸銨及克枯爛會造成幼穗分化期，及孕穗期的水稻單株產量降低，其中穗數的差異較小，每穗粒數、稔實率及千粒重則明顯減少，以幼穗分化期施用之影響最大。由胚根伸長抑制反應之殺菌劑藥害潛力，依序為鐵鉀砷酸銨、克枯爛及撲克拉最高，次為亞賜圃及滅達樂，快得寧之植物毒性最低，免賴地及賓克隆對水稻較安全，比多農及多得淨則對水稻及胡瓜均較安全。由胚根伸長抑制結果推估，6.5%鐵鉀砷酸銨溶液稀釋2000倍，及10%克枯爛可濕性粉劑稀釋1000倍之田間登記使用量，遠低於50%胚根伸長抑制劑量（鐵鉀砷酸銨為20ppm，克枯爛為25ppm)，因此避免於穀粒發育之敏感生育期施用，應不致發生產量降低之藥害現象。測試殺蟲劑藥害潛力依序為滅克蝨、益滅松、亞滅寧、美文松及陶斯松最高，次為納乃得，四氯異苯腈、蟎離丹、護賽寧、丁基加保扶及芬普寧之植物毒性最低，護粒松對水稻極為安全，對萵苣之毒性較高。測試除草劑藥害潛力依序為免速隆、百速隆、丁基拉草、巴拉刈及撻乃安最高，次為樂滅草，固殺草僅在萵苣之表現較敏感，伏寄普及施得圃對水稻之毒性高，在胡瓜及萵苣極為安全。

MAFA and tecloftalam are widely used fungicides for controlling sheath blight and bacterial leaf blight on transplanted rice in Taiwan. It shows inadequate use at sensitive growth stages could result in phytotoxicity of rice plant. A study was conducted to investigate the effect of MAFA and tecloftalam applied at various developmental stages on the performance of yield and yield components of rice plants. Tested fungicides were sprayed over-top to potted plants at panicle initiation stage, booting stage and heading stage. Symptoms of panicle twisting and stigma necrosis appeared after tested fungicides spraying at panicle initiation stage and booting stage. Plant yield was significantly affected by MAFA and tecloftalam treatments at different stages except that at heading stage. Among the yield components, filled-grain percentage and 1000-grain weight decreased markedly. The reduction in yield might be due to inhibition of effective grains filling by tested pesticides. Bioassay methods were developed using cucumber, lettuce and rice as the test species to evaluate the phytotoxicity of pesticides. Dose-response relationships were established for the radical elongation of each test crop and chemical. Based on the data presented here, this bioassay appeared to be useful in evaluating the potential toxicity of pesticides to crops.