Memari Zahra, Karimi Javad, Kamali Shokoofeh, Goldansaz Seyed Hossein, Hosseini Mojtaba
Biocontrol and Insect Pathology Laboratory, Department of Plant Protection, School of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.
College of Agriculture and Natural Resources, University of Tehran, Karaj Campus, Iran.
J Nematol. 2016 Dec;48(4):261-267. doi: 10.21307/jofnem-2017-034.
The carob moth () is the key pest of pomegranate, which causes a significant percentage of losses in pomegranate orchards and warehouses of Iran annually. The pest larvae are characterized by displaying a cryptic behavior within the fruit, which avoids most routine control techniques, especially chemical method. The low efficiency of traditional measurements and also the rich species diversity of natural enemies within the infested fruits highlight the necessity of exploring effective control methods, especially environmental friendly approaches. Entomopathogenic nematodes (EPNs) are a group of biological control agents that actively search for the host, including those in a cryptic habitat like the carob moth larvae within infested fruits. Here, we assumed that treatment of the infested and dropped fruits with EPNs may provide new insight into the management of the carob moth. Three species of EPNs, , , and were selected and used in a series of in vitro and in vivo experiments. In preliminary assays, the EPNs species were used with different concentrations of infective juveniles (IJs) (0, 1, 5, 10, 25, and 50 IJ/larvae) in 2-cm diam. plates. The mortality rates of the laboratory tests were 79.75% and 76.5% for and , corresponded to LC value of 2.02 IJ/larva for and 2.05 IJ/larva for . On the contrary, demonstrated low virulence on the pest larvae in petri tests with a LC = 426.92 IJ/larva. Hence, both species were selected for subsequent experiments. The penetration rate for and into the hemocoel of the pest was 43% and 31%, respectively, and the corresponding reproduction rate was 15,452 IJ/larva for and 18,456 IJ/larva for . The gathered data from those in vitro tests were used for a field assay. Different concentrations (5, 10, 50, 100, and 160 IJ/cm of the arena) of and were applied in the field test. The mean mortality results from the last test were 10.89% and 26.65% for and , respectively. Finally, we found that these low virulence rates of the nematodes were attributed to inhibitory/repellency effects of saprophytic fungi within the infested pomegranates, a usual status of the infested fruits in autumn or winter seasons. Future work on additional EPN populations more adapted to the extreme conditions of the pomegranate production area in Iran may provide sufficient evidence to continue the further investigation on the best EPN species populations and advanced formulations with high durability.
角额壁蜂是石榴的主要害虫，每年在伊朗的石榴园和仓库中造成相当大比例的损失。该害虫幼虫的特点是在果实内表现出隐匿行为，这使得大多数常规防治技术，尤其是化学方法失效。传统防治措施效率低下，且受侵染果实内天敌种类丰富，这凸显了探索有效防治方法的必要性，尤其是环境友好型方法。昆虫病原线虫是一类生物防治剂，能够主动寻找宿主，包括在受侵染果实内处于隐匿栖息地的角额壁蜂幼虫。在此，我们假设用昆虫病原线虫处理受侵染并掉落的果实可能为角额壁蜂的管理提供新的思路。选择了三种昆虫病原线虫，即[线虫种类1]、[线虫种类2]和[线虫种类3]，并用于一系列体外和体内实验。在初步试验中，将这些昆虫病原线虫种类与不同浓度的感染性幼虫（IJs）（0、1、5、10、25和50条IJs/幼虫）在直径为2厘米的培养皿中使用。实验室测试中，[线虫种类1]和[线虫种类2]的死亡率分别为79.75%和76.5%，[线虫种类1]的LC值为2.02条IJs/幼虫，[线虫种类2]的LC值为2.05条IJs/幼虫。相反，[线虫种类3]在培养皿试验中对害虫幼虫的毒力较低，LC值为426.92条IJs/幼虫。因此，选择了这两种[线虫种类1和2]进行后续实验。[线虫种类1]和[线虫种类2]进入害虫血腔的穿透率分别为43%和31%，相应的繁殖率分别为[线虫种类1]的15452条IJs/幼虫和[线虫种类2]的18456条IJs/幼虫。从这些体外试验收集的数据用于田间试验。在田间试验中应用了不同浓度（5、10、50、100和160条IJs/cm试验区域）的[线虫种类1]和[线虫种类2]。最后一次试验的平均死亡率结果显示，[线虫种类1]和[线虫种类2]分别为10.89%和26.65%。最后，我们发现线虫的这些低毒力率归因于受侵染石榴内腐生真菌的抑制/驱避作用，这是秋冬季节受侵染果实的常见状况。未来对更适应伊朗石榴产区极端条件的其他昆虫病原线虫种群的研究可能会提供充分证据，以便继续进一步研究最佳的昆虫病原线虫种类种群和具有高耐久性的先进制剂。
