Characterising insect plant host relationships facilitates understanding multiple host use

Abstract

Weed biocontrol relies on host specificity testing, usually carried out under quarantine conditions to predict the future host range of candidate control agents. The predictive power of host testing can be scrutinised directly with Aconophora compressa, previously released against the weed Lantana camara L. (lantana) because its ecology in its new range (Australia) is known and includes the unanticipated use of several host species. Glasshouse based predictions of field host use from experiments designed a posteriori can therefore be compared against known field host use. Adult survival, reproductive output and egg maturation were quantified. Adult survival did not differ statistically across the four verbenaceous hosts used in Australia. Oviposition was significantly highest on fiddlewood (Citharexylum spinosum L.), followed by lantana, on which oviposition was significantly higher than on two varieties of Duranta erecta (''geisha girl'' and ''Sheena's gold''; all Verbenaceae). Oviposition rates across Duranta varieties were not significantly different from each other but were significantly higher than on the two non-verbenaceous hosts (Jacaranda mimosifolia D. Don: Bignoneaceae (jacaranda) and Myoporum acuminatum R. Br.: Myoporaceae (Myoporum)). Production of adult A. compressa was modelled across the hosts tested. The only major discrepancy between model output and their relative abundance across hosts in the field was that densities on lantana in the field were much lower than predicted by the model. The adults may, therefore, not locate lantana under field conditions and/or adults may find lantana but leave after laying relatively few eggs. Fiddlewood is the only primary host plant of A. compressa in Australia, whereas lantana and the others are used secondarily or incidentally. The distinction between primary, secondary and incidental hosts of a herbivore species helps to predict the intensity and regularity of host use by that herbivore. Populations of the primary host plants of a released biological control agent are most likely to be consistently impacted by the herbivore, whereas secondary and incidental host plant species are unlikely to be impacted consistently. As a consequence, potential biocontrol agents should be released only against hosts to which they have been shown to be primarily adapted.

Relative host plant species use by the lantana biological control agent Aconophora compressa (Membracidae) across its native and introduced ranges

“…The categorisations derived here correlate well with those derived from nymphal rearing experiments across the host plants sampled in Australia (Manners and Walter, 2009) and also from adult performance tests on these plants (Manners et al, 2010). The results presented here also demonstrate that the host plant associations of A. compressa are consistent across geographic regions sampled, in terms of which plant species are used as primary, secondary or incidental hosts (Figs.…”

“…In general, the results presented here provide further support that fiddlewood is the primary host plant of A. compressa in Australia and that all other hosts, including lantana, are secondary or incidental hosts (Manners and Walter, 2009;Manners et al, 2010). A. compressa has been recorded on particular lantana plants for periods of about 26 weeks (double that recorded in this study - Table 2) and at moderately high levels (about three to five times that recorded in this study) in 2009 and 2010, at the Alan Fletcher Research Station, Sherwood, Brisbane, Australia.…”

“…Aconophora compressa was introduced into Australia from Mexico in 1995 for the biological control of lantana (Lantana camara L.: Verbenaceae) (Palmer et al, 1996) but in Australia is mostly associated with fiddlewood (Citharexylum spinosum L.: Verbenaceae) (Dhileepan et al, 2006;Manners and Walter, 2009;Manners et al, 2010), a tree native to the Caribbean. The available data for A. compressa from field and laboratory studies indicate that fiddlewood is a primary host, whereas lantana and the varieties of D. erecta, (i.e.…”

“…The available data for A. compressa from field and laboratory studies indicate that fiddlewood is a primary host, whereas lantana and the varieties of D. erecta, (i.e. geisha girl and Sheena's gold) are secondary hosts (Dhileepan et al, 2006;Manners and Walter, 2009;Manners et al, 2010).…”

“…compressa is ideal for investigating aspects of the herbivorehost interaction that are relevant to the pre-release evaluation of biocontrol agents because it uses multiple hosts, much of its basic biology on a number of hosts is known (Manners and Walter, 2009;Manners et al, 2010), and it has already been introduced into a new area where it interacts with hosts differently from the way originally anticipated. Furthermore, a number of plant species exist in both Mexico and Australia for which the insect plant interaction has been studied in Australia, including D. erecta (variety not known in Mexico), jacaranda (Jacaranda mimosifolia), lantana (L. camara in Australia is thought to be most closely related to L. urticifolia from Mexico (Scott 2002), although recent evidence suggests that it may be more closely related to lantana from Venezuela and the Dominican Republic (R. Watts, CSIRO, Plant Industries, Canberra, personal communication).…”