Biol Invasions (2010) 12:2895–2912 DOI 10.1007/s10530-010-9735-6 ORIGINAL PAPER Micro-managing arthropod invasions: eradication and control of invasive arthropods with microbes Ann E. Hajek • Patrick C. Tobin Received: 15 May 2009 / Accepted: 23 September 2009 / Published online: 31 March 2010 Ó Springer Science+Business Media B.V. 2010 Abstract Non-indigenous arthropods are increas- arthropod management programs within a general ingly being introduced into new areas worldwide and context, and compare the use of microbes in gypsy occasionally they cause considerable ecological and moth management with diverse microbes being economic harm. Many invasive arthropods particu- developed for use against other invasive arthropods. larly pose problems to areas of human habitation and native ecosystems. In these cases, the use of Keywords Arthropod pathogens Á environmentally benign materials, such as host-spe- Augmentation biological control Á Biological cific entomopathogens, can be more desirable than invasions Á Classical biological control Á broader spectrum control tactics that tend to cause Containment Á Eradication Á Lymantria dispar greater non-target effects. The majority of successful eradication programs using arthropod pathogens have targeted invasive Lepidoptera with Bacillus thurin- Introduction giensis kurstaki (Btk), such as eradication efforts against the gypsy moth, Lymantria dispar (L.), in The introduction of non-native arthropods in natural North America and New Zealand. Both Btk and areas such as wetlands and forests is increasing in Lymantria dispar nucleopolyhedrovirus have been frequency due to the relatively recent waves of successfully used in efforts to limit the spread of increased global trade and travel (National Research L. dispar in the United States. For invasive arthropod Council 2002; Work et al. 2005; Brockerhoff et al. species that are well established, suppression pro- 2006; Liebhold et al. 2006; McCullough et al. 2006). grams have successfully used arthropod-pathogenic Some introductions result in the successful establish- viruses, bacteria, fungi and nematodes for either ment of an invasive species that in turn causes short- or long-term management. We will summarize considerable environmental and economic harm to the use of pathogens and nematodes in invasive the functioning and composition of native communi- ties and ecosystems (Parker et al. 1999; Mack et al. 2000; Pimentel et al. 2005). Generally, the invasive A. E. Hajek (&) Department of Entomology, Cornell University, Ithaca, species that receive the most attention are those that NY 14853-2601, USA alter communities and ecosystems, sometimes irre- e-mail: [email protected] versibly, over a geographically broad area. As we increase our awareness and ability to detect new P. C. Tobin USDA Forest Service, Northern Research Station, introductions, more invasive species could be com- Morgantown, WV 26505-3101, USA bated before their inimical effects are irreversible. 123 2896 A. E. Hajek, P. C. Tobin Efforts to combat invasive species begin with reproducing individual of a species or the reduction of prevention of introduction and establishment. In some their population density below sustainable levels’’ instances, the arrival of a new species is detected early (Myers et al. 2000). Debate on the feasibility of enough to prevent establishment through intervention eradication has been quite contentious in the past strategies (Veitch and Clout 2002; Glare 2009; Hajek (DeBach 1964; Knipling 1979; Carey 1991). Dahlsten and Tobin 2009; Simberloff 2009), or the founder and Garcia (Dahlsten and Garcia 1989) edited a survey population size is insufficient to successfully establish of efforts to eradicate invasive arthropod species and even without use of control tactics (Williamson and plant pathogens and argued that eradication programs Fitter 1996; Simberloff and Gibbons 2004). Numerous were often crisis situations and focused heavily on use countries have developed risk assessments to define of chemical pesticides without adequate knowledge of those species that are known to arrive frequently, pests and systems being treated. Of the 12 eradication mostly due to trade, and that have the potential for programs described in their book, only four were establishment and costly impacts; thus, many detection considered successful. However, the low rate of efforts specifically target these commonly-introduced eradication success does not necessarily argue against invaders arriving along known pathways (Committee attempting eradication if, for example, the benefits of on the Scientific Basis for Predicting the Invasive eradication exceed the costs of the effort (Regan et al. Potential of Nonindigenous Plants and Plant Pests in 2006; Edwards and Leung 2009). the United States 2002). There is also recognition of the While eradication of an unwanted arthropod is importance of ballast water in the introduction of indeed possible (Simberloff 2009), success is only aquatic species and the need to manage this invasion likely under relatively strict conditions (Myers et al. pathway (Ruiz et al. 2000; Drake and Lodge 2004). 2000). General guidelines have been developed pre- The identification of important invasion pathways senting criteria that are necessary for success in and vectors as well as those species likely to be eradication: effective methods for detection and con- introduced help to optimize available, yet usually trol, authority to do what is needed, measures to limited, resources to maintain surveillance programs at prevent reinvasion, and funding, because eradication ports-of-entry. However, given the volume of global campaigns are usually quite costly (Myers et al. 2000). trade and travel, and the fact that only a very small Additional costs would also be required to ecologi- proportion of pathways and vectors are checked, many cally restore the impacted area following an eradica- species still become introduced despite these efforts tion effort (Myers et al. 2000; Hall and Hastings 2007). (Work et al. 2005; Brockerhoff et al. 2006; Liebhold Restoring an ecosystem to the conditions existing prior et al. 2006; McCullough et al. 2006). For example, to establishment of an invasive is difficult, especially Brockerhoff et al. (2006) reported that roughly 10% of when the native flora and fauna present before the shipments entering New Zealand are inspected by invasive established had not been well documented. quarantine officers, while \2% of cargo entering the In the event that eradication efforts are initially not United States is inspected (Work et al. 2005; feasible or become infeasible, the subsequent options McCullough et al. 2006). In addition, some species are to attempt control through containment or pop- are not considered as pests in their native ranges but are ulation suppression, or to do nothing. In general, considerably more problematic when introduced into methods for controlling arthropods have been devel- new regions, such as the emerald ash borer [Agrilus oped for many diverse systems and pests over many planipennis (Fairmaire)] invasion of North America years but, the standard methods have generally (Poland and McCullough 2006) and the fall webworm targeted pests of managed resources, in particular invasion [Hyphantria cunea (Drury)] of Asia (Gomi agriculture and forestry. However, many of the tactics 2007). Thus, efforts to prevent introductions of only and especially the use of chemical pesticides to known pests can be inadequate. control arthropod pests in managed systems such as If establishment of a non-native arthropod has not agricultural and horticultural crops, are not appropri- been prevented, and a newly established species is ate for use outside of these systems due to pesticide considered to be potentially harmful, then the first label regulations. In natural areas and especially those management approach considered is often eradication. areas that are publicly-owned such as federal- or Eradication is the forced ‘‘removal of every potentially state-managed areas, there are regulations restricting 123 Micro-managing arthropod invasions 2897 pest control practices (e.g., National Environmental using microbes for arthropod control has been exten- Policy Act) due to concerns regarding, for example, sively evaluated and the microbes that are used are the potential for non-target effects and toxicity to predominantly very host specific (Hajek 1999; humans and wildlife. These regulations can prohibit Hokkanen and Hajek 2003; O’Callaghan and the use of broad spectrum tactics, such as use of Brownbridge 2009), especially in comparison with chemical pesticides. Moreover, in urban areas, there most chemical insecticides. can be considerable human objection to any man- In this review, we will first present successful agement interventions against invasive arthropods examples of the use of a microbial biopesticide to (e.g., East Bay Pesticide Alert 2009), which increases eradicate non-native arthropod species. We will then the need for environmentally benign tactics. Thus, focus on the use of pathogens and parasitic nema- methods for controlling invasive arthropods must be todes in the management of spread and population tailored for individual ecosystems being impacted by suppression of established non-native invasive arthro- a particular invasive species and, depending on the pods. In particular, management efforts aimed at area, tactics often must be environmentally benign. eradicating, containing, and suppressing populations Invasive species