Caoili Barbara L, Latina Romnick A, Sandoval Regina Faye C, Orajay Joey I
Institute of Weed Science, Entomology, and Plant Pathology, College of Agriculture and Food Science, University of the Philippines Los Baños, College Laguna, 4031, Philippines.
Del Monte Philippines, Inc., Camp Philips, Manolo Fortich, Bukidnon, 8705, Philippines.
J Nematol. 2018 Sep 3;50(2):99-110. doi: 10.21307/jofnem-2018-024.
In search for local entomopathogenic nematode (EPN) species as a biological control agent of lepidopterous insect pests of corn, a survey for EPN in the major islands in the Philippines was conducted. Seven EPN populations from 279 soil samples were isolated using Ostrinia furnacalis, the key target insect pest of corn in the country, as bait. Analysis of the ITS1-5.8S-ITS2 ribosomal DNA sequence revealed the presence of Steinernema abbasi, Steinernema minutum , Steinernema tami , and Heterorhabditis indica . The pathogenicity of these EPN was tested in Ostrinia furnacalis , Spodoptera litura , and Helicoverpa armigera larvae under laboratory conditions. All the EPN isolates were pathogenic to the lepidopteran species with, H. indica PBCB and S. abbasi MBLB exhibiting the highest virulence (88%-99.33% and 90%-100% mortality, respectively) at 48 hr post infection (HPI) and thus, further studies were done on these two EPN. The highest penetration rate at 48 HPI was observed in H. armigera infected with S. abbasi MBLB (28.15%), while the lowest was in O. furnacalis infected with H. indica PBCB (14.25%). Nonetheless, based on LC 50 at 48 HPI, H. indica PBCB was most virulent to S. litura (8.89 IJ per larva), but not significantly different from O. furnacalis (10.52 IJ per larva). Steinernema abbasi MBLB was most virulent to O. furnacalis (10.98 IJ per larva), but not significantly different to S. litura (17.08 IJ per larva). LT 50 estimates showed that O. furnacalis was significantly the most susceptible to H. indica PBCB (21.90 hr) and S. abbasi (21.18 hr). Our results suggest that H. indica PBCB and S. abbasi MBLB are good candidates as biological control agents against these insect pests of corn. Moreover, O. furnacalis as alternative bait for EPN was discussed. To date, this is the most extensive research on Philippine EPN, comprised of wide sampling coverage, molecular identification and bioefficacy assays.
为寻找当地昆虫病原线虫（EPN）物种作为玉米鳞翅目害虫的生物防治剂，在菲律宾的主要岛屿开展了EPN调查。以该国玉米的主要靶标害虫亚洲玉米螟为诱饵，从279份土壤样本中分离出7个EPN种群。对ITS1-5.8S-ITS2核糖体DNA序列进行分析，结果显示存在阿巴西斯氏斯氏线虫、微小斯氏线虫、塔米斯氏线虫和印度异小杆线虫。在实验室条件下，对这些EPN在亚洲玉米螟、斜纹夜蛾和棉铃虫幼虫中的致病性进行了测试。所有EPN分离株对鳞翅目物种均具有致病性，印度异小杆线虫PBCB和阿巴西斯氏斯氏线虫MBLB在感染后48小时（HPI）时表现出最高毒力（死亡率分别为88%-99.33%和90%-100%），因此，对这两种EPN进行了进一步研究。在感染阿巴西斯氏斯氏线虫MBLB的棉铃虫中，48 HPI时观察到最高穿透率（28.15%），而在感染印度异小杆线虫PBCB的亚洲玉米螟中最低（14.25%）。尽管如此，根据48 HPI时的LC50，印度异小杆线虫PBCB对斜纹夜蛾的毒力最强（每头幼虫8.8 IJ），但与亚洲玉米螟（每头幼虫10.52 IJ）无显著差异。阿巴西斯氏斯氏线虫MBLB对亚洲玉米螟的毒力最强（每头幼虫10.98 IJ），但与斜纹夜蛾（每头幼虫17.08 IJ）无显著差异。LT50估计值表明，亚洲玉米螟对印度异小杆线虫PBCB（21.90小时）和阿巴西斯氏斯氏线虫（21.18小时）最为敏感。我们的结果表明，印度异小杆线虫PBCB和阿巴西斯氏斯氏线虫MBLB是防治这些玉米害虫的良好生物防治候选剂。此外，还讨论了亚洲玉米螟作为EPN替代诱饵的问题。迄今为止，这是对菲律宾EPN最广泛的研究，包括广泛的采样覆盖、分子鉴定和生物效能测定。
