Behavioral and electrophysiological responses of Coptotermes formosanus Shiraki towards entomopathogenic fungal volatiles Abid Hussain a,⇑ , Ming-Yi Tian a , Yu-Rong He a , John M. Bland b , Wen-Xiang Gu c a Department of Entomology, College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510640, China b United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, 1100 Robert E Lee Blvd, New Orleans, LA 70124, USA c Department of Chemistry, College of Sciences, South China Agricultural University, Guangzhou 510640, China article info Article history: Received 9 November 2009 Accepted 30 August 2010 Available online 29 September 2010 Keywords: Fungal volatiles HS-SPME Repellency Virulence Workers abstract Termites adjust their response to entomopathogenic fungi according to the profile of fungal volatile organic compounds (VOCs). This study demonstrates the pathogenicity of Metarhizium anisopliae, Beau- veria bassiana and Isaria fumosorosea (=Paecilomyces fumosoroseus) towards the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Using no-choice assays, M. anisopliae was found to be highly virulent (LT 50 3.10 d) when compared to B. bassiana (LT 50 6.62 d) and I. fumosoro- sea (LT 50 12.39 d). Also using choice assays, the foraging behavior of C. formosanus was determined in the presence of pathogenic fungi. The highly pathogenic fungi (M. anisopliae) elicited a repellent response, causing most of the termites to forage in a safe zone farthest from the fungal source. This repellency resulted in relatively low mortality similar to the controls. The repellency of M. anisopliae conidia can be used to protect human belongings and timber from termites. While I. fumosorosea cultures were not repellent to C. formosanus workers, the termites were highly susceptible to infection. Electroantenno- graphic responses of workers showed approximately 47% and 78% lower level of response to conidia of B. bassiana and I. fumosorosea, respectively, as compared to M. anisopliae. The VOC profile of repellent cul- tures of M. anisopliae mainly consisted of paraffins (60.97%), while the major proportion of the I. fumos- orosea profile consisted of branched and cyclic alkanes (84.41%). From the above findings, we conclude that the incorporation of I. fumosorosea may increase the control potential of bait. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Termites are highly likely to be exposed to natural enemies that include predators, parasites and pathogens during foraging. Among these natural enemies, fungi are especially important pathogens of insects and many fungi thrive in the same environment as termites. Conditions in a termite nest, including moderate temper- ature and high humidity, are conducive to the growth of fungal species and are important factors in fungal survival and propaga- tion (Kramm et al., 1982). In spite of this, few studies have been able to demonstrate consistent and effective control of termite colonies using fungi or fungal preparations in the field (Rath, 2000). Reasons for this lack of success include both physiological and behavioral mechanisms that termites have evolved to resist infec- tion by disease agents. Physiological mechanisms include cellular and humoral immune responses (Rosengaus et al., 2007; Chouvenc et al., 2009) and antifungal chemical production in termite nests by nest mates, which are primarily composed of fecal material (Rosengaus et al., 1998), sternal and salivary gland secretions (Rosengaus et al., 2004). Behavioral mechanisms include the use of allogrooming to remove fungal conidia from the surface of the cuticle of nest mates (Rosengaus et al., 1998; Shimizu and Yamaji, 2003), walling-off of infected areas of a colony (Milner et al., 1998; Staples and Milner, 2000), pathogen alarm behavior which warns nestmates about the presence of lethal fungi causing them to leave the area (Rosengaus et al., 1999; Myles, 2002) and removal of fun- gal-infected termites (Grace and Zoberi, 1992; Jones et al., 1996; Rath, 2000; Myles, 2002). The work explored in many of the studies mentioned above was focused on the avoidance behavior of termites towards repellent entomopathogenic fungi. The authors Staples and Milner (2000); Myles (2002); Mburu et al. (2009) interpreted that repellency of termites towards virulent strains of entomopathogenic fungi served as a means to eliminate the chance of fungal epizootics in the nest. Furthermore, they suggested that repellency occurred mainly because of variations in the composition of volatile blends emitted by different strains. However, no attempt has been made to compare the volatile organic compounds (VOCs) of entomopath- ogenic fungi in the past. Recent studies by Mburu et al. (2009) on Metarhizium anisopliae and Beauveria bassiana suggested that 1049-9644/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.biocontrol.2010.08.009 ⇑ Corresponding author. E-mail address: solvia_aah@yahoo.com (A. Hussain). Biological Control 55 (2010) 166–173 Contents lists available at ScienceDirect Biological Control journal homepage: www.elsevier.com/locate/ybcon