Survey of Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae) Parasitoids in Guangxi, China1

The rice leaffolder,Cnaphalocrocis medinalisGuenée (Lepidoptera: Pyralidae), is a migratory insect pest that inflicts significant damage to rice, Oriza sativa L. (Poaceae), in Asia. Reports of damage caused by C. medinalis have increased in several Asian countries in recent decades (Wang et al. 2009). Although cultural, biological and chemical control strategies, including the use of transgenic rice varieties, have been developed (Nathan et al. 2006, Xu et al. 2011, Gurr et al. 2012, Cho et al. 2013,Huang et al. 2014, Punithavalli et al. 2013),many farmers still use insecticides (such as abamectin, amino-avermectin benzoate and chlorantraniliprole) as the main management tools against C. medinalis. Excessive use of insecticides can lead to the development of resistance (Zheng et al. 2011, Zhang et al. 2014, Wang et al. 2016), reduction of natural enemy populations (Ren et al. 2015), and pest resurgence. Natural enemies play an important role in regulating insect pest populations in the field. More than 100 parasitoid species in Ichneumonidae, Braconidae and Chalcidoidea were reported as natural enemies of C. medinalis in Asia (Lou et al. 2013). Nineteen parasitoid species were identified in Nanning, Guangxi Autonomous Region, China (Ren et al. 2015). In Tieăn Giang, Vietnam, C. medinalis larval parasitism rates ranged from 33–90% in rice fields not treated with insecticide applications (Gurr et al. 2012). In Guangdong Province, China, parasitism reached 65.7% in the early-season rice, with Stenomesius maculatus Liao (Hymenoptera: Eulophidae) responsible for 62.5% of total parasitism (Li 1992). Huang et al. (2013) reported that S. maculatus achieved 39.2% parasitism in Guangxi,China.Parasitism byApanteles cyprisNixon (Hymenoptera:Braconidae) was 63.4% in Guizhou Province, China (Ma et al. 2013). Ren et al. (2015) reported that 74% fewer parasitoids were collected from pesticide-treated fields than from untreated fields in Guangxi, China, suggesting that applications of nitenpyram, buprofezin, pymetrozine and avermectin (customary to rice production in China) severely disrupted the activity and abundance of parasitoids. A better understanding of natural parasitism is important to conserve biological control agents.We carried out surveys betweenApril andNovember 2011 at the