Prey stage preference and functional and numerical responses of Neoseiulus barkeri Hughes (Acari: Phytoseiidae) to eggs of Raoiella indica Hirst (Acari: Tenuipalpidae)

Raoiella indica Hirst (Acari: Tenuipalpidae) is a polyphagous pest widely dispersed worldwide and a particular threat to crops from the Arecaceae family. Control measures are still being evaluated in recently invaded countries. A possible control strategy for this pest is the use of predatory mites. A recent study has suggested Neoseiulus barkeri Hughes (Acari: Phytoseiidae) as a potential biological control agent of R. indica. In the present study we determined the prey stage preference of N. barkeri when offered different stages of R. indica besides its functional response and numerical over its prey stage preferred. The predatory mite N. barkeri showed a marked preference for eggs over other stages of the prey. The regression analysis indicated that the predatory mite N. barkeri exhibited a Type II functional response. The prey density needed to start the oviposition was 10 R. indica eggs. The number of eggs laid by N. barkeri females increased with an increase in the prey density and tended to stabilize when prey availability was greater than 80 R. indica eggs, with average oviposition of 2 eggs/female. Our study suggests that N. barkeri shows potential to reduce populations of R. indica, especially at low prey densities. However, further studies are needed to investigate whether R. indica supports the development of immature stages of N. barkeri.

Functional response and prey stage preference of Neoseiulus barkeri on Trasonemus confusus

The fungivorous Tarsonemus confusus Ewing is a tarsonemid mite causing a so call ‘black-dot’ symptom on the bagged apple fruit in North China, and the phytoseiid mite Neoseiulus barkeri Hughes is a cosmopolitan generalist predator of many agricultural and horticultural pests. In the present study, we evaluated the biological control potential of N. barkeri on T. confusus, by determining its functional response type to prey density of and prey stage preference on both active and quiescent life stages of T. confusus (i.e., eggs, larvae, quiescent larvae and female adults). We found that N. barkeri exhibited all three types of functional response. When fed on eggs and quiescent larvae of T. confusus, N. barkeri had a Type II functional response (i.e., inverse density-dependent predation rate); however, a Type I functional response (i.e., density-independent predation rate) was detected when N. barkeri preyed on T. confusus larvae and a Type III functional response (i.e., sigmoid density-dependent predation rate) when preyed on T. confusus adults. We further showed that the ‘constant prey’ functional response models fit our data better than the ‘depleted prey’ models, as the predator left and reencountered the previously fed prey which reduced its searching efficiency. When all active and quiescent life stages of T. confusus were available, N. barkeri significantly preferred larvae over other prey stages for feeding. Our results imply that due to its quick response to the increasing prey larval and adult densities, N. barkeri could consume a great number of active prey and is thus capable to decline the current fruit damage caused by prey feeding and to potentially prevent the prey population build-up later in the season. Furthermore, predators with Type II response may be efficient at low prey densities, thus augmentative release of N. barkeri early in the season may also suppress the egg and quiescent larva populations of T. confusus. Knowledge from this study provides insights into our understandings in the biological control ecology of N. barkeri.

Influence of Feeding with different Plant Pollens on Prey- Stage Preference and Predation Rate of Neoseiulus Californicus (Mcgregor) (Acari: Phytoseiidae)

Neoseiulus californicus (Acari: Phytoseiidae) is an effective predator in greenhouses which feeds on plant injurious mites. Searching capacity is one of importance in the effectiveness of this predatory mite. In this research, the population fed with corn pollen, walnut and date pollen and the spider mite (four strains) were investigated. The prey-stage preference of N. californicus was studied on different developmental stages of Tetranychus urticae. The predation rate of rearing population of N. californicus was determined; it was used eggs of T. urticae. Experiments were carried out on strawberry disc in Petri dish (6 cm diameter) under laboratory conditions (27±1ºC temperature, 70±5% RH and 16L: 8D photoperiod). After 24 hours, the total numbers of prey consumed were counted. The predatory mites reared on different pollens prefer eggs or nymphs to adults and the Preference Index of different strains was not different. Result of consumed of spider mites by female predatory mites indicated the predation rate of the predatory mites fed with corn pollen (9±1.46), walnut pollen (8.19±0.99) and Date pollen (8.28±0.80) did not any significant difference, however when spider mites and the mentioned pollens were used, the predation rate of predatory mites when fed with T. urticae (14.74±0.94), Walnut (15.24±1.05) and date pollen (14.17±1.04) show significant difference with the population of corn pollen (10.0±0.95). The predation rate of four strains decreased at present of plant pollens. Use of the predatory mite fed with the different developmental stage of two-spotted spider mite and pollen in the biological control of the pests is useful.