‘New species association’ biological control? Two coccinellid species and an invasive psyllid pest in New Zealand

The ‘new species association’ biological control approach is based on the ecological principle in which a natural enemy is used that has not coevolved with a pest. The recent incursion of the tomato–potato psyllid (TPP), Bactericera cockerelli to New Zealand offered a unique opportunity to investigate the potential of a new species association for biological control of this pest. This laboratory-based study investigated the potential for a new species association between two New Zealand naturalized coccinellids, Cryptolaemus montrouzieri and Cleobora mellyi, and TPP. A third naturalized New Zealand coccinellid, Scymnus loewii, was compared as a potential ‘old association’. We conducted two experiments to determine consumption rate and feeding behavior, respectively, of adults and fourth-instar larvae of the three coccinellid species on mixed instars of TPP nymphs, using tomato and potato leaflets, and a no-leaflet control. C. montrouzieri consumed up to 30 psyllids over 24 h, depending on leaflet type and predator life stage. C. mellyi adults and larvae were the most voracious predators of psyllids, consuming up to 100 TPP over 24 h. Adult C. mellyi spent more time feeding on psyllids in the control (56%) and potato leaflets (30%) than on tomato leaflets. Larvae spent 79% more time feeding on the no-leaflet control, compared to the potato (24%) and tomato leaflet (14%) treatments. S. loewii consumed relatively few psyllids on all three substrates (<10 over 24 h), and spent less time feeding compared to the other two species. By demonstrating that these predators will consume this psyllid, our results suggest that a new species association may potentially exist between C. montrouzieri, C. mellyi and the TPP.

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► Two naturalized Australian coccinellid species consumed the invasive tomato–potato psyllid pest.
► Coccinellid size and life stage affected the number of psyllids consumed.
► Feeding substrate influenced psyllid consumption.