Plant Health Division, International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya.
Faculty of Life Sciences, Division Urban Plant Ecophysiology, Humboldt-Universität zu Berlin, Lentzeallee, Berlin, Germany.
J Econ Entomol. 2018 Aug 3;111(4):1587-1594. doi: 10.1093/jee/toy135.
Cowpea, Vigna unguiculata ((L.) Walp; Fabales: Fabaceae), is an important indigenous vegetable and grain legume in the tropics where it represents a major diet component. Cowpea aphid, Aphis craccivora (Koch; Hemiptera: Aphididdae) is a major pest causing up to 100% yield losses. Aiming at establishing alternative approach to synthetic insecticides, we evaluated the pathogenicity of 23 fungal isolates including Metarhizium anisopliae ((Metschn.) Sorokin; Hypocreales: Clavicipitaceae), Beauveria bassiana ((Bals.) Vuill.; Hypocreales: Cordycipitaceae), and Isaria sp. (Hypocreales: Cordycipitaceae) against adult A. craccivora in the laboratory. Adult apterous aphids were sprayed with conidial suspensions titred at 1 × 108 conidia ml-1 for pathogenicity tests while 1 × 104, 1 × 105, 1 × 106, 1 × 107 and 1 × 108 conidia ml-1 were used in dose response bioassays. All the fungal isolates were found pathogenic to A. craccivora, causing mortality of between 34.5 and 90%. The lethal 50% mortality time (LT50) values varied between 3.3 and 6.3 d, with the best isolates being ICIPE 62, ICIPE 41 and ICIPE 644. The lethal concentration mortality (LC50) values were 2.3 × 106, 1.3 × 108 and 1.3 × 109 for ICIPE 62, ICIPE 41, and ICIPE 644, respectively. M. anisopliae isolate ICIPE 62 produced more conidia on aphid cadavers (4.5 × 107) than ICIPE 41 (2.7 × 107) and ICIPE 644 (2.1 × 107) 6 d post-treatment. Relative potency comparison showed that ICIPE 62 was more potent than the other two isolates. In the screenhouse, conidia of ICIPE 62 significantly reduced A. craccivora population compared to control but there was no significant difference between emulsifiable and aqueous formulations. Small-holder leafy vegetable producers could gain more profits using fungal-based biopesticides in Aphid-IPM strategies, leading to reduction of pre-harvest intervals after their application compared to synthetic insecticides.
菜豆，豇豆（L.）Walp; 豆科：豆科，是热带地区重要的本土蔬菜和粮食豆科植物，是主要的饮食成分之一。豇豆蚜虫，Aphis craccivora（Koch；半翅目：蚜科）是一种主要害虫，可造成高达 100%的产量损失。为了建立替代合成杀虫剂的方法，我们评估了 23 种真菌分离物的致病性，包括绿僵菌（Metschn.）Sorokin；子囊菌目：拟青霉科）、球孢白僵菌（Bals.）Vuill.; 子囊菌目：白僵菌科）和伊莎里氏菌（Hypocreales：白僵菌科）对实验室中成年 A. craccivora 的致病性。用浓度为 1×108 个分生孢子 ml-1 的分生孢子悬浮液喷洒无翅蚜虫成虫进行致病性试验，而在剂量反应生物测定中使用 1×104、1×105、1×106、1×107 和 1×108 个分生孢子 ml-1。所有真菌分离物均对 A. craccivora 具有致病性，导致死亡率在 34.5%至 90%之间。半致死时间（LT50）值在 3.3 至 6.3 d 之间变化，最好的分离物是 ICIPE 62、ICIPE 41 和 ICIPE 644。ICIPE 62、ICIPE 41 和 ICIPE 644 的致死浓度致死率（LC50）值分别为 2.3×106、1.3×108 和 1.3×109。绿僵菌分离物 ICIPE 62 在处理后 6 天内对蚜虫尸体（4.5×107）的产孢量高于 ICIPE 41（2.7×107）和 ICIPE 644（2.1×107）。相对效力比较表明，ICIPE 62 比其他两种分离物更有效。在温室中，与对照相比，ICIPE 62 的分生孢子显著降低了 A. craccivora 的种群，但可乳化和水基制剂之间没有显著差异。与合成杀虫剂相比，使用基于真菌的生物农药的菜豆蚜虫综合防治（IPM）策略可使小农户获得更多利润，在应用后可缩短收获前间隔。
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