Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, USA.
PLoS One. 2013 May 1;8(5):e62632. doi: 10.1371/journal.pone.0062632. Print 2013.
Insect-killing fungi such as Beauveria bassiana are being evaluated as possible active ingredients for use in novel biopesticides against mosquito vectors that transmit malaria. Fungal pathogens infect through contact and so applications of spores to surfaces such as walls, nets, or other resting sites provide possible routes to infect mosquitoes in and around domestic dwellings. However, some insects can detect and actively avoid fungal spores to reduce infection risk. If true for mosquitoes, such behavior could render the biopesticide approach ineffective. Here we find that the spores of B. bassiana are highly attractive to females of Anopheles stephensi, a major anopheline mosquito vector of human malaria in Asia. We further find that An. stephensi females are preferentially attracted to dead and dying caterpillars infected with B. bassiana, landing on them and subsequently becoming infected with the fungus. Females are also preferentially attracted to cloth sprayed with oil-formulated B. bassiana spores, with 95% of the attracted females becoming infected after a one-minute visit on the cloth. This is the first report of an insect being attracted to a lethal fungal pathogen. The exact mechanisms involved in this behavior remain unclear. Nonetheless, our results indicate that biopesticidal formulations comprising B. bassiana spores will be conducive to attraction and on-source visitation by malaria vectors.
球孢白僵菌等杀虫真菌正被评估为新型生物农药的潜在有效成分，用于防治传播疟疾的蚊子媒介。真菌病原体通过接触感染，因此将孢子应用于墙壁、网或其他栖息场所等表面，为感染室内外蚊子提供了可能的途径。然而，一些昆虫可以检测到并主动避开真菌孢子，以降低感染风险。如果蚊子也是如此，这种行为可能会使生物农药方法无效。在这里，我们发现球孢白僵菌的孢子对亚洲主要疟蚊媒介按蚊属斯蒂芬斯的雌性蚊子极具吸引力。我们进一步发现，按蚊属斯蒂芬斯的雌性蚊子更喜欢感染了球孢白僵菌的死虫和垂死的毛毛虫，落在上面，随后被真菌感染。雌性蚊子也更喜欢喷洒油状白僵菌孢子的布，在布上停留一分钟后，有 95%的吸引雌性蚊子被感染。这是昆虫被致命真菌病原体吸引的第一个报告。这种行为涉及的确切机制尚不清楚。尽管如此，我们的研究结果表明，包含球孢白僵菌孢子的生物农药配方将有利于吸引和疟疾媒介的来源访问。
