以低風險防治資材管理荔枝椿象 (半翅目：荔椿科)

Abstract

荔枝椿象 (Tessaratoma papillosa (Drury, 1770)) 不僅造成荔枝 (Litchi chinensis Sonn.) 及龍眼 (Dimocarpus longan Lour.) 嚴重的損失，其分泌之臭液，亦危及民眾安全，研究荔枝椿象各種防治方法為重要的課題。本論文以賽洛寧 (lambda-cyhalothrin)、第滅寧 (deltamethrin)、芬殺松 (fenthion) 及亞滅培 (acetamiprid) 四個已核准於荔枝及龍眼的化學殺蟲劑對荔枝椿象若蟲、成蟲及平腹小蜂 (Anastatus formosanus Crawford) 進行感受性實驗，局部滴定法生物檢定實驗中，一齡若蟲對第滅寧感受性最高，成蟲對芬殺松感受性最高，而荔枝椿象一齡若蟲及成蟲對亞滅培的感受性最差；但在龍眼苗盆栽試驗中，以亞滅培登記濃度 50 mg/L 施藥 7 天後對荔枝椿象一齡若蟲防治率為 93.44 ± 2.61%。因此，推論上述化學殺蟲劑對荔枝椿象防治效果均良好。但對平腹小蜂的毒性高於荔枝椿象成蟲及若蟲，平腹小蜂對賽洛寧、第滅寧、芬殺松及亞滅培的 48 小時後半數致死劑量 LD50 介於 0.0298~0.8268 ng/parasitoid，該些劑量皆低於荔枝椿象成蟲對此等有效成分之半數致死劑量 LD50 32.92~420.2 ng/insect且略低於荔枝椿象一齡若蟲，其 LD50 範圍介於 0.0392~8.556 ng/insect。本論文另外以低風險資材，如礦物油 (mineral oil)、苦楝油 (neem oil) 及脂肪酸鉀鹽 (potassium salts of fatty acids, FAPS) 進行相關實驗，發現以浸漬方式施用脂肪酸鉀鹽 4,900 ppm 能造成荔枝椿象一齡若蟲 100% 死亡率，且效果是低風險資材中最好的。此外，脂肪酸鉀鹽對平腹小蜂的 48 小時半致死濃度為 7,266 mg/L，高於荔枝椿象一齡及三齡若蟲的 694.5 及 665.1 mg/L，相較於化學藥劑而言，脂肪酸鉀鹽對平腹小蜂相對較安全。龍眼苗盆栽試驗中，脂肪酸鉀鹽 4,900 mg/L 對荔枝椿象一齡若蟲防治率為 80.28 ± 6.97%，脂肪酸鉀鹽 9,800 mg/L 對荔枝椿象三及五齡若蟲防治率分別為 80.06 ± 7.18 及 63.08 ± 3.11%。脂肪酸鉀鹽登記濃度 4,900~9,800 mg/L 對荔枝椿象若蟲有防治效果，但本研究試驗結果顯示，脂肪酸鉀鹽對玉荷包品種荔枝的花器會造成嚴重藥害，且對龍眼幼果造成輕微藥害，建議可以針對聚集於葉部之若蟲局部施用，避免傷害到花器及幼果。

Tessaratoma papillosa (Drury, 1770) not only causes significant damage to litchi (Litchi chinensis Sonn.) and longan (Dimocarpus longan Lour.) but can also cause harm to humans because of the irritating and corrosive effluvial fluid they excrete. Therefore, it is critical to develop methods for managing T. papillosa. This study tested the susceptibility of T. papillosa and parasitoid wasps (Anastatus formosanus Crawford) toward four chemical insecticides registered for use on litchi and longan (namely, lambda-cyhalothrin, deltamethrin, fenthion, and acetamiprid). Topical bioassay results showed that T. papillosa first-instar nymphs and adults had the highest respective susceptibility toward deltamethrin and fenthion, and both exhibited the lowest susceptibility toward acetamiprid. However, results of greenhouse trials conducted on longan plants indicated that acetamiprid had 93.44 ± 2.61% control efficacy toward T. papillosa first-instar nymphs. In summary, these four chemical insecticides show high control efficacy toward T. papillosa, but the 48-hour LD50 values for the four chemical insecticides in A. formosanus ranged from 0.0298~0.8268 ng/parasitoid, which was lower than the LD50 values for T. papillosa first-instar nymphs and adults, namely 0.0392~8.556 and 32.92~420.2 ng/insect, respectively. Additional dipping assay experiments testing the control efficacy of low-risk agents mineral oil, neem oil and potassium salts of fatty acids (FAPS) found that 4,900 ppm FAPS caused 100% mortality in T. papillosa first-instar nymphs, displaying the highest efficacy of all concentrations. Moreover, the 48-hour LC50 values of FAPS in A. formosanus was 7,266 mg/L, higher than the 48-hour LC50 values of FAPS in T. papillosa first- and third-instar nymphs, namely 606.6 and 665.1 mg/L. Compared with the aforementioned four chemical pesticides, FAPS is a relatively safe agent for use on A. formosanus. Results of greenhouse trials conducted on longan plants indicated that 4,900 ppm FAPS had 80.28 ± 6.97% control efficacy toward T. papillosa first-instar nymphs, and 80.06 ± 7.18 and 63.08 ± 3.11% control efficacy toward T. papillosa third- and fifth-instar nymphs at 9,800 ppm. FAPS under these concentrations showed promising control efficacy toward T. papillosa nymphs, and greenhouse trials conducted on litchi plants showed that FAPS caused serious phytotoxic effects on litchi flowers and slight phytotoxic effects on longan young fruits. Therefore, growers should avoid applying FAPS to litchi and longan flowers and young fruits.