Understanding Heliothine (Lepidoptera: Heliothinae) Pests: What is a Host Plant? Author(s): John Paul Cunningham and Myron P. Zalucki Source: Journal of Economic Entomology, 107(3):881-896. 2014. Published By: Entomological Society of America URL: http://www.bioone.org/doi/full/10.1603/EC14036 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. REVIEW Understanding Heliothine (Lepidoptera: Heliothinae) Pests: What is a Host Plant? 1 2,3 JOHN PAUL CUNNINGHAM AND MYRON P. ZALUCKI J. Econ. Entomol. 107(3): 881Ð896 (2014); DOI: http://dx.doi.org/10.1603/EC14036 ABSTRACT Heliothine moths (Lepidoptera: Heliothinae) include some of the worldÕs most dev- astating pest species. Whereas the majority of nonpest heliothinae specialize on a single plant family, genus, or species, pest species are highly polyphagous, with populations often escalating in size as they move from one crop species to another. Here, we examine the current literature on heliothine host-selection behavior with the aim of providing a knowledge base for research scientists and pest managers. We review the host relations of pest heliothines, with a particular focus on Helicoverpa armigera (Hu¨ bner), the most economically damaging of all heliothine species. We then consider the important question of what constitutes a host plant in these moths, and some of the problems that arise when trying to determine host plant status from empirical studies on host use. The top six host plant families in the two main Australian pest species (H. armigera and Helicoverpa punctigera Wallengren) are the same and the top three (Asteraceae, Fabaceae, and Malvaceae) are ranked the same (in terms of the number of host species on which eggs or larvae have been identiÞed), suggesting that these species may use similar cues to identify their hosts. In contrast, for the two key pest heliothines in the Americas, the Fabaceae contains Ϸ1/3 of hosts for both. For Helicoverpa zea (Boddie), the remaining hosts are more evenly distributed, with Solanaceae next, followed by Poaceae, Asteraceae, Malvaceae, and Rosaceae. For Heliothis virescens (F.), the next highest Þve families are Malvaceae, Asteraceae, Solanaceae, Convolvulaceae, and Scrophulariaceae. Again there is considerable overlap in host use at generic and even species level. H. armigera is the most widely distributed and recorded from 68 plant families worldwide, but only 14 families are recorded as a containing a host in all geographic areas. A few crop hosts are used throughout the range as expected, but in some cases there are anomalies, perhaps because host plant relation studies are not comparable. Studies on the attraction of heliothines to plant odors are examined in the context of our current understanding of insect olfaction, with the aim of better understanding the connection between odor perception and host choice. Finally, we discuss research into sustainable management of pest heliothines using knowledge of heliothine behavior and ecology. A coordinated international research effort is needed to advance our knowledge on host relations in widely distributed polyphagous species instead of the localized, piecemeal approaches to understanding these insects that has been the norm to date. KEY WORDS polyphagy, host relation, volatile, pest management Heliothines are a group of noctuid moths whose larvae AsteraceaeÑ74%; see also Mitter et al. 1993). These feed predominantly on ßowers and plant reproductive Þgures suggest a high degree of host specialization in structures, giving these insects a variety of common most heliothines, as is common in phytophagous in- names, such as bollworm, budworm, earworm, pod sects (Jermy 1984). borer, and ßower caterpillar (Zalucki et al. 1986). Although only a few heliothines are considered to Worldwide there are some 365 species in the subfam- be polyphagous, some of these species are widely ily (Cho et al. 2008). In North America, 148 heliothine known and studied, and are some of the worldÕs most species in 14 genera have been described (Hardwick important agricultural pests. These pest species ap- 1996, Knudson et al. 2003), with host plants recorded pear to be in a single “Heliothis” clade, suggesting the for 92 of these species; based on these records, we trait was inherited from a common ancestor (Cho et estimate 55% have been recorded as having been al. 2008). Heliothis virescens (F.) and Helicoverpa zea found on a single host species, 83% from a single genus, (Boddie) are the main heliothine pests in North and and 96% from a single plant family (predominantly South America (Bergvinson 2005) where these moths have been recorded from 235 plant species in 36 fam- 1 School of Earth, Environmental and Biological Sciences, Queens- ilies, with a large overlap in host plant use for the two land University of Technology, Brisbane 4001, Australia. 2 species (see compilation by Kogan et al. 1989). To- School of Biological Sciences, The University of Queensland, Ͼ Brisbane 4072, Australia. bacco budworm (He. virescens) infests 19 crops, 3 Corresponding author, e-mail: [email protected]. while the corn earworm, H. zea, infests at least 30 0022-0493/14/0881Ð0896$04.00/0 ᭧ 2014 Entomological Society of America 882 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 107, no. 3 (Blanco et al. 2007). These moths are important pests compared with adult traits (host Þnding and recogni- of crops, such as maize, cotton, soybean, tomato, to- tion)? Are there common attributes of host species that bacco, alfalfa; horticultural crops such as beans, sweet serve as deÞnitive host cues? Are there differences in the corn, and tomato; as well as ßoriculture crops such as way host cues are perceived in specialist and generalist chrysanthemum. As the name implies, the tobacco species? Are there particular behavioral traits present in budworm shows a preference for laying eggs on the polyphagous heliothine species that have enabled them Solanaceae (e.g., tobacco and tomato), while H. zea to successfully use agro-ecosystems? (the corn earworm) prefers hosts in the Poaceae Determining the extent and nature of polyphagy is (maize, sorghum; Bergvinson 2005). However, a wide essential for understanding the behavioral- and evo- range of crops can support these pests, as we show in lutionary ecology of heliothines (Cho et al. 2008), and the following analysis of host use. In addition to these in the design and implementation of effective pest major pest species, other heliothines have been recorded management strategies (Jallow et al. 2004). Here, we from more than one plant family in North AmericaÑ use published studies on polyphagous heliothines to Heliothis borealis (Hampson) (four families), Heliothis further our understanding of what constitutes a “host oregonica (Hy. Edwards) (three families), Schinia tertia plant.” We begin by carrying out a simple analysis of (Grote) (two families), and Schinia olivacea Smith (two host plant use in the four major pest species, to in- families)Ñbut none are regarded as pests. vestigate whether particular plant species, or families, Helicoverpa armigera (Hu¨ bner) is widespread are favored as hosts. We then review information on throughout Europe, Africa, Asia, and Australia, where host preferences, and evidence for innate (genetic) it causes extensive damage to a wide range of crops and acquired (learnt) differences in these preferences (Zalucki et al. 1986, Sharma 2005). More recently the within species, exploring additional physiological de- species has spread to South America (Czepak et al. terminants of host plant use. Focusing on olfaction in H. 2013, Specht et al. 2013, Tay et al. 2013), with devas- armigera, we investigate how current knowledge of sen- tating effects in the broad acre cropping systems in sory biology can help our understanding of host choice Brazil (C. Czepak, personal communication). Cer- and polyphagy. We conclude by considering how an tainly the presence of a diverse indigenous heliothine in-depth knowledge of the nature of polyphagy might be fauna and similar polyphagous pests has not prevented applied to pest management of some of the worldÕs most its establishment and spread. The area in the new economically important species. world at risk of H. armigera invasion extends well beyond Brazil as suggested by Zalucki and Furlong Host Plant Use by Polyphagous Heliothines (2005) using a simple CLIMEX model. The species has the potential to spread into the southern United States, What Constitutes a Host? Before presenting an with seasonal migration much further north (D. J. analysis of host use in polyphagous heliothines, we Kriticos, unpublished data). must Þrst consider how well host plant