The Papua New Guinea University of Technology, Department of Agriculture, Lae 411, Morobe Province, Papua New Guinea.
University of Southern Queensland, Centre for Crop Health, Institute for Agriculture and the Environment, Research and Development Division, Toowoomba 4350, Australia.
J Invertebr Pathol. 2017 Sep;148:67-72. doi: 10.1016/j.jip.2017.05.010. Epub 2017 Jul 17.
Metarhizium anisopliae has a wide range of coleopteran hosts, including weevils. Some susceptible insects are known to modify their behavior to prevent infection, typically detecting virulent strains by olfaction, and avoiding physical contact with sources of infection. Laboratory olfactometer assays were conducted on the sweetpotato weevil Cylas formicarius to test the hypothesis that insects would avoid a more virulent strain of M. anisopliae when presented with a strain of low virulence or an untreated control. When adult weevils were allowed to choose between paired test arenas containing sweetpotato roots and M. anisopliae isolates on agar cores, weevils avoided arenas with the highly virulent isolate QS155, showing a preference for either roots with uninoculated agar cores or cores with the low virulence isolate QS002-3. When roots or whole sweetpotato plants were inoculated with M. anisopliae, the preferences of weevils remained broadly similar; weevils were repelled by the highly virulent isolate QS155 when tested against either QS002-3 or uninoculated roots and plants, however weevils were not repelled by the low virulence isolate QS002-3 tested against uninoculated controls. When single-sex groups of weevils were tested separately in the olfactometer using uninoculated whole plants and plants treated with isolate QS155, males and females responded similarly and statistically identical preferences were found for the untreated plants. When weevils were released singly at different times of the day the response time for males was significantly shorter in the afternoon compared to the morning. Males were always significantly faster to respond to olfactory stimuli than females. Understanding factors that may lead to avoidance of virulent M. anisopliae strains by C. formicarius will be an essential part of developing an 'attract-and-infect' strategy for the management of C. formicarius.
金龟子绿僵菌有广泛的鞘翅目宿主，包括象鼻虫。一些易感染的昆虫已知会改变它们的行为以防止感染，通常通过嗅觉检测毒力菌株，并避免与感染源物理接触。对甘薯象鼻虫 Cylas formicarius 进行了实验室嗅觉计测定，以检验昆虫在接触低毒力菌株或未处理对照时是否会避免更毒力的金龟子绿僵菌菌株的假设。当成年象鼻虫被允许在含有甘薯根和琼脂核心上的金龟子绿僵菌分离物的成对测试区之间选择时，象鼻虫避免了含有高毒力分离物 QS155 的区，表现出对未接种琼脂核心的根或低毒力分离物 QS002-3 的偏好。当用金龟子绿僵菌接种根或整个甘薯植物时，象鼻虫的偏好仍然大致相似；当测试对 QS002-3 或未接种的根和植物时，高毒力分离物 QS155 会排斥象鼻虫，但当测试对未接种的对照物时，低毒力分离物 QS002-3 不会排斥象鼻虫。当在嗅觉计中使用未接种的整个植物和用分离物 QS155 处理的植物对单独的单性象鼻虫组进行测试时，雄性和雌性的反应相似，并且对未处理的植物发现了统计学上相同的偏好。当象鼻虫在一天中的不同时间单独释放时，雄性的反应时间在下午明显短于早晨。雄性对嗅觉刺激的反应速度始终明显快于雌性。了解可能导致 C. formicarius 回避毒力金龟子绿僵菌菌株的因素，将是开发针对 C. formicarius 的“吸引-感染”策略的重要组成部分。
