Abstract:
The tomato/potato psyllid (TPP), Bactericera cockerelli, is a serious pest that causes significant damage to various vegetable and fruit crops. It is a newly invasive pest species in New Zealand since its accidental introduction in 2006. This study is a series of experiments in the laboratory and greenhouse to compare and evaluate the efficiency of two commercially available species of predatory mites (Amblydromalus limonicus and Neoseiulus cucumeris) as potential biocontrol agents of TPP. The first experiment determined predatory preference between eggs and 1st instar nymphs of TPP under choice and no-choice conditions. The second experiment examined the functional and numerical response at constant densities (2, 4, 8, 12, 16, 20, 24 and 28) of TPP eggs and 1st instar nymphs. Both laboratory experiments were conducted under a controlled temperature (25°C), relative humidity (85%) and 14:10 h light:dark (L:D) photoperiod. Results indicated under no-choice conditions, A. limonicus consumed approximately twice as many eggs and 1st instar nymphs as N. cucumeris. Under choice conditions, A. limonicus ate twice as many eggs and 4 times as many1st instar nymphs as N. cucumeris. Both A. limonicus and N. cucumeris preferred TPP eggs over 1st instar nymphs. Both species displayed a type two functional response. A. limonicus had a higher attack rate (approximately 3 times greater) than N. cucumeris, although N. cucumeris had a higher handling time (approximately 2 times greater). The third experiment involved a realistic approach which involved controlling TPP on capsicum plants under experimental greenhouse conditions (at an average temperature of 25 ± 1ºC, average relative humidity at 70 ± 5%, and photoperiod of 16:8 L:D). Results indicated that both A. limonicus and N. cucumeris could reduce TPP population growth and its damage to capsicum plants significantly. It further showed that both species performed almost equally well at the end of the experiment. This opens up a new biocontrol option given that N. cucumeris can be easily and more cheaply mass reared than A. limonicus. This suggests that this predatory mite can potentially be used as a more cost-effective biological control agent for the control of TPP.
