Variation in plant quality frequently impacts the biology of herbivorous insects. This variability can affect the outcome of biological control projects, especially during colonization of incipient populations and mass production. The invasive species Melaleuca quinquenervia is a weed of Florida that decreases biodiversity of natural areas. At least two chemical variants of M. quinquenervia occur in Florida, each differing in their foliar terpenoid profiles dominated by either viridiflorol or E-nerolidol. Biological control efforts against this weed resulted in the introduction of two insect species. The second agent released was a psyllid, Boreioglycaspis melaleucae. Described herein are results describing changes in the levels of secondary metabolites from plants of each chemotype when fertilized at three levels. Additionally, the results of psyllid feeding studies are presented describing the influence of these factors on the performance and oviposition choice. The results indicate that despite generally lower nitrogen content and increased secondary metabolite concentration in the viridiflorol chemotype, little change in psyllid biology was observed when fed leaves of this chemotype. Chemotype differences primarily influenced oviposition preference, where more than twice the number of eggs were laid on the viridiflorol chemotype. Nymphal development time was also delayed 0.7-day when fed leaves of the viridiflorol chemotype. Regardless of chemotype, nymphal survival increased, and development time decreased when fed leaves from the higher fertilizer level. The difference in susceptibility between the psyllid B. melaleucae and the weevil Oxyops vitiosa may be explained by differences in feeding behavior, whereby the psyllid feeds selectively inside leaves and avoids secondary metabolites stored in oil glands.
Reference: Wheeler, G. and K. Ordung (2005). “Secondary metabolite variation affects the oviposition preference but has little effect on the performance of Boreioglycaspis melaleucae: a biological control agent of Melaleuca quinquenervia.” Biological Control 35(2): 115-123.