Abstract In a 3-step approach, three series of experiments were carried out to assess the virulence and environmentally-dependent biocontrol potential of entomopathogenic nematodes from Cameroon against two cassava insect pests, Stictococcus vayssierei and its trophobiotic ant, Anoplolepis tenella, under laboratory and screenhouse conditions. In the first series, 20 isolates (18 Heterorhabditis baujardi, 1 Steinernema cameroonense, and 1 S. nyetense) were separately checked for their ability to infect the two pests at a rate of 500 infective juveniles (IJs)/insect for 36 h, and to select the most virulent isolates. All isolates were pathogenic to both pests, and caused 10% to 90% and 0 to 63% mortality of S. vayssierei and A. tenella, respectively. In a second series of virulence bioassays, 2 sets of 4 selected isolates were examined for: (a) concentration-response, (b) time-response, and (c) reproduction. Stictococcus vayssierei mortality ranging from 56 to 62% were observed at doses of 75–100 IJs/insect within 24–36 h. Nematodes at doses of 100–500 IJs/insect caused 51% mortality within 36 h. Nematodes successfully reproduced in both pests. The third bioassay series investigated migration and host preference abilities of selected isolates as well as nematode attachment to ants. The dispersal of IJs as affected by soil moisture and soil type was studied under screenhouse conditions. Nematodes exhibited positive attraction to both pests, yet with no preferential movement of IJs. Nematode dispersal and persistence (up to 89 days) were favored in sandy clay loam soils at pF 3.5 and pF 4.2 (9–15% moistures). The results from this study are sufficiently encouraging to embark on in situ testing. For integrated S. vayssierei control, implications such as the development of an adequate field application method to be used at field conditions are discussed, as even moderate levels of control might be economically profitable.

中文翻译：

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喀麦隆本土昆虫病原线虫对介壳虫 Stictococcus vayssierei 和抚育蚂蚁 Anoplolepis tenella 的生物防治潜力

摘要 在一个三步法中，进行了三个系列的实验，以评估喀麦隆昆虫病原线虫对两种木薯害虫 Stictococcus vayssierei 及其滋养蚂蚁 Anoplolepis tenella 的毒力和环境依赖性生物防治潜力，在实验室和屏蔽室下使适应。在第一个系列中，分别检查了 20 个分离株（18 个 Heterorhabditis baujardi、1 个 Steinernemacameroonense 和 1 个 S.nyetense）以 500 只感染性幼虫 (IJ)/昆虫 36 小时的速度感染这两种害虫的能力，和选择毒性最强的分离株。所有分离株对这两种害虫都具有致病性，并分别导致 S. vayssierei 和 A. tenella 10% 至 90% 和 0 至 63% 的死亡率。在第二个系列的毒力生物测定中，对 2 组 4 种选定的分离株进行了检查：(a) 浓度响应，(b) 时间响应，和 (c) 繁殖。在 24-36 小时内以 75-100 IJ/昆虫的剂量观察到 Stictococcus vayssierei 死亡率为 56% 至 62%。剂量为 100-500 IJ/昆虫的线虫在 36 小时内导致 51% 的死亡率。线虫在两种害虫中都成功繁殖。第三个生物测定系列研究了选定分离株的迁移和宿主偏好能力以及线虫对蚂蚁的附着。在筛网条件下研究了受土壤水分和土壤类型影响的 IJ 的扩散。线虫对这两种害虫都表现出积极的吸引力，但没有 IJ 的优先运动。在 pF 3.5 和 pF 4.2（湿度 9-15%）的砂质粘壤土中，线虫的传播和持久性（最多 89 天）是有利的。这项研究的结果足以令人鼓舞，可以着手进行原位测试。对于集成的 S. vayssierei 控制，讨论了诸如开发在田间条件下使用的适当的田间应用方法等含义，因为即使是中等水平的控制也可能在经济上有利可图。