Evaluation of the efficacy of non-pesticide substances to control two spotted spider mite (Tetranychus urticae) on strawberry

草莓 (Fragaria ananasa) 是臺灣地區所產的重要鮮食水果之一，擁有很高的經濟價值，故有充足誘因促使農民投注資金發展設施栽培，例如網室、溫室以及植物工廠。然而，不論是種植在室外或是溫室內，二點葉蟎 (Tetranychus urticae) 都可能對草莓造成危害，進而造成重大經濟損失。由於傳統防治常使用的化學藥劑防治法會衍生抗藥性及果實殘毒等問題，故以安全有效的非農藥蟲害防治資材來防治草莓二點葉蟎，對於草莓的害蟲管理是一個理想的對策。本研究中以窄域油、木醋液、皂液、糖醋液進行設施栽培之草莓二點葉蟎防治試驗。碟盤試驗的結果顯示這些非農藥資材中，致死效力最高的是以水稀釋 200 倍的窄域油及皂液，但致死率皆只有58.3% 及 61.7%，均低於傳統化學藥劑對照組阿巴汀稀釋 2000 倍液 (98.3%)，代表這些非農藥資材對二點葉蟎的觸殺毒性 (contact toxicity) 不高。由植株試驗中發現，以水稀釋 200 倍的窄域油及皂液之致死率於噴灑後 72 小時可高達到88.3% 及 86.7%，表示資材噴灑是否均勻對於其致死效力非常重要。在防治試驗中，經過稀釋 200 倍的窄域油及皂液處理後七天之二點葉蟎成若蟎防治率分別達到 91.1% 及 84.2%，顯示具有良好的防治成效；而稀釋 200 倍的木醋液之致死率雖然偏低，但其防治率亦可達到 62%，仍可對二點葉蟎達到一定程度的防治效力，推測此資材有其他因素能抑制二點葉蟎的族群密度。未來可採用適宜的施用方法，利用窄域油及皂液這兩種資材對溫室及植物工廠內的害蟎進行防治。Strawberry is an important crop of high economic value in Taiwan, and it is one of reasons farmers invest a lot of money to develop facility cultivation such as nethouses, greenhouses and plant factories. However, the crop is threatened by several tiny pests both in the field and greenhouses. Among them, the two-spotted spider mite (Tetranychus urticae) is one of the most common and serious pests of strawberry. Chemical control is a conventional method for controlling the mite, but there are some problems with using pesticides to control T. urticae. Pesticides can cause serious problems such as resistance in T. urticae populations and residues on the fruit. Therefore, it would be beneficial to find some safer and more efficient non-pesticide substances for pest control on strawberry. In this study, narrow-range oils, and wood-vinegar, soap, and sugar-vinegar solutions were tested for their efficiency in controlling T. urticae on facility-cultivated strawberries. The results of the dish test indicated that narrow-range oils and the soap solution at a 200-fold dilution produced the highest mortality rates among these non-pesticide substances with respective mortality rates of 58.3% and 61.7%, but these were lower than that of abamectin (98.3%). Moreover, in the potted strawberry test, mortality rates of narrow-range oils (88.3%) and the soap solution (86.7%) at a 200-fold dilution were very high after 72 h of treatment. In the control experiment, respective control rates for narrow-range oils and soap solution at a 200-fold dilution were 91.1% and 84.2%. This indicates that T. urticae was efficiently controlled using these substances. Moreover, results showed that the wood-vinegar solution at a 200-fold dilution produced a low mortality rate, but it still had the some control effect on the T. urticae population. The control rate with the wood-vinegar solution was 62%. It is suspected that some other factors suppress the population density of T. urticae. In the future, narrow-range oil and soap solutions will be applied to control mites on strawberries in greenhouses and plant factories