Pure forests are often seen as being more prone to damage by specialist pest insects than mixed forests, and particularly mixed forests associating host and nonhost species. We addressed the effect of tree diversity on oak colonization and defoliation by a major specialist pest, the oak processionary moth (OPM) We quantified the number of male OPM moths captured and larval defoliation in pure stands of two oak host species (Quercus robur and Quercus petraea) and in mixed stands associating the two oak species or each oak species with another nonhost broadleaved species. We conducted two complementary studies to test the effect of host species and stand composition: (i) we used pheromone trapping to compare the number of males OPM captured throughout the distribution of oak hosts in France and (ii) we noted the presence of OPM nests and estimated defoliation in mature forests of north‐eastern France. Oak species and stand composition significantly influenced the number of male OPM captured and defoliation by OPM larvae. Quercus petraea was consistently more attractive to and more defoliated by OPM than Q. robur. Both oak trees were attacked more in pure stands than in mixed stands, in particular mixed stands associating oaks with another (nonhost) broadleaved species. The results of the present study support the view that mixed forests are more resistant to specialist pest insects than pure stands, and also indicate that this trend depends on forest composition. Our study provides new insights into OPM ecology and has potential implications for forest management, including the management of urban forests where OPM causes serious human health issues.

中文翻译：

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树种特性和森林组成影响信息素陷阱中捕获的橡树蛾的数量和幼虫落叶的强度

与混交林，尤其是将寄主和非寄主物种相关联的混交林，人们通常认为纯林更容易受到专业害虫的破坏。我们通过一种主要的专业害虫橡树行蛾 (OPM) 解决了树木多样性对橡树定植和落叶的影响 我们量化了两种橡树寄主物种 (Quercus robur 和 Quercus) 的纯林分中捕获的雄性 OPM 飞蛾的数量和幼虫的落叶petraea) 并在混合林中将两种橡树种或每种橡树种与另一种非寄主阔叶树种联系起来。我们进行了两项补充研究来测试寄主物种和林分组成的影响：(i) 我们使用信息素诱捕来比较在法国橡树宿主的整个分布中捕获的雄性 OPM 的数量，以及 (ii) 我们注意到法国东北部成熟森林中 OPM 巢穴的存在和估计的落叶。橡树树种和林分组成显着影响了 OPM 幼虫捕获的雄性 OPM 的数量和落叶。Quercus petraea 始终比 Q. robur 对 OPM 更具吸引力且更容易落叶。两种橡树在纯林中比在混合林中受到的攻击更多，特别是将橡树与另一种（非寄主）阔叶树种联系起来的混合林。本研究的结果支持混交林比纯林更能抵抗特殊害虫的观点，并且还表明这种趋势取决于森林组成。