Effectiveness of Two Predatory Mite Species (Acari: Phytoseiidae) in ControllingDiaphorina citri(Hemiptera: Liviidae)

Abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is the insect vector of huanglongbing (HLB), the most devastating citrus disease in the world. The objective of this study was to evaluate the efficacy of two species of commercially available predatory mites, Neoseiulus cucumeris (Oudemans) and N. barkeri (Hughes) (Acari: Phytoseiidae), against D. citri. The predatory mites were evaluated by (1) determining their prey stage preference under no-choice conditions by providing eggs, 1st and 2nd instar nymphs; (2) determining the functional and numerical responses of the predators to varying densities of eggs (from 2 to 32/leaf disk); and (3) evaluating the control effect of N. cucumeris on D. citri on caged trees of Citrus reticulata Blanco in the field, using 1 to 8 sachets (900 ± 100 adult mites per sachet) per tree. The results indicated that N. cucumeris consumed eggs of D. citri only, whereas N. barkeri consumed eggs and 1st instar nymphs. Both predators displayed a Type III functional response (sigmoid). A single female adult of N. cucumeris consumed significantly more D. citri eggs than N. barkeri. N. cucumeris could lay eggs when feeding exclusively on D. citri eggs. The field experiment showed that control effect on D. citri was significantly correlated with the number of N. cucumeris released. Two or more sachets released per tree could achieve significant control at an initial density of 30 adult D. citri (male: female = 1:1) per tree. Improvement of field control efficacy of N. cucumeris on D. citri is discussed.