Acquired Natural Enemies of the Weed Biological Control Agent Oxyops Vitiosa (Colepotera: Curculionidae) (Report‪)‬

Acquisition of novel natural enemies may influence the successful establishment, spread, and impact of introduced weed biological control agents in their adventive range (Goeden & Louda 1976; Semple & Forno 1987; Simberloff 1989; Cornell & Hawkins 1993; Hill & Hulley 1995; McPartland & Nicholson 2003; Norman et al. 2009; Paynter et al. 2010). Of the arthropods introduced for control of invasive plants world wide, approximately 50% suffer sufficient mortality from higher trophic levels to significantly limit suppression of target weeds (Goeden & Louda 1976). The spider mite Tetranychus lintearius (Dufour), for example, was introduced into New Zealand, Australia, and the United States as a biological control agent of the invasive plant Ulex europaeus L. (Fabaceae) (Hill & Stone 1985; Hill et al. 1991). Although successfully established and widely distributed, mites in each country rarely sustained sufficient population densities to provide permanent control of the target weed (Rees & Hill 2001). Subsequent studies demonstrated that a complex of native and introduced predators suppressed T. lintearius populations and limited control of the invasive weed (Peterson 1993; Peterson et al. 1994; Pratt et al. 2003). Considering the ecological risks (Carvalheiro et al. 2008) and expense of biological control, increased attention in the scientific literature has focused on predicting susceptibility of introduced biological control agents to natural enemies in the adventive range (Kuhlmann et al. 2006). Hill & Hulley (1995), for instance, demonstrated that variation in susceptibility of introduced herbivores to parasitoids is related, in part, to evolutionary strategies that render the prey less accessible, apparent, or palatable to the attacker. Along this continuum of use by natural enemies lie those species that are highly apparent yet experience relatively less attack due to the expression of chemical deterrents that render them less palatable or even toxic to prospective natural enemies. The introduced weevil Oxyops vitiosa Pascoe sequesters terpenoids from leaves of its host plant Melaleuca quinquenervia (Cav.) S. T. Blake and larvae excrete these compounds through their integument (Wheeler et al. 2002). The consumption and expression of these terpenoids repels the red imported fire ant (Solenopsis invicta Buren) and red wing blackbird (Agelaius phoeniceus L.) under controlled feeding tests (Wheeler et al. 2002). It remains unclear, however, if this acquired repellency confers protection from the suite of potential novel natural enemies that exist in the herbivore's adventive range.