Evaluation of Stratiolaelaos scimitus and Neoseiulus barkeri for biological control of thrips on greenhouse cucumbers

Stratiolaelaos scimitus Berlese (Acari: Laelapidae) is an important soil-dwelling predatory mite used to control thrips and it is necessary to explore its potential predation capacity. In the present study, the functional response for S. scimitus on the pupae of Frankliniella occidentalis Pergande was examined. In addition, the effects of released S. scimitus for the control of Thrips tabaci Lindeman and F. occidentalis on greenhouse cucumber were evaluated, and compared with that of the common predator Neoseiulus barkeri Hughes (Acari: Phytoseiidae). The results showed that S. scimitus exhibited a Holling type II functional response on thrips pupae. The greenhouse study indicated that the release of N. barkeri and S. scimitus separately at the density of 250 mites/m² suppressed the population growth of thrips. In comparison with control plots, N. barkeri and S. scimitus reduced the population of T. tabaci by 76% and 64% in six weeks, respectively. Releases of N. barkeri and S. scimitus led to a reduction in F. occidentalis by 41% and 43%, respectively. Significantly lower densities of both thrips species per leaf were recorded in treatments of individual releases of N. barkeri or S. scimitus than that in the control plots. The findings highlight the potential for utilising N. barkeri and S. scimitus as biological control agents of T. tabaci and F. occidentalis, respectively.     

Use of polypropylene bags for mass rearing Neoseiulus baraki (Acari: Phytoseiidae), a predatory mite of Aceria guerreronis Keifer (Acari: Eriophyidae)

An efficient, low cost and practicable mass rearing method for the predatory mite, Neoseiulus baraki Athias-Henriot (Acari: Phytoseiidae) was developed using a bag made of two-ply polypropylene (gauge 150, 24 cm × 36 cm) sheets. Introducing 20 N. baraki females into the bag produced a mean number 5218 ± 212.10 offspring in 6 weeks with a 260-fold increase of the initial population.     

To be an intra‐guild predator or a cannibal: is prey quality decisive?

Abstract.  1. Many cannibalistic species are also intra-guild predators. Such predators will often face the decision whether to consume a conspecific or a heterospecific prey from the same guild. This decision may depend on the relative quality and abundance of the prey but also on other factors such as relatedness by descent, prey-specific defence and the probability of the victim harbouring shared diseases.
2. Here, intra-guild interactions among two cannibalistic species of predatory mites, Iphiseius degenerans and Neoseiulus cucumeris (Acari: Phytoseiidae) that belong to closely related genera were studied.
3. Individuals of I. degenerans were offered a diet of conspecifics or heterospecifics. Because I. degenerans is capable of recognising kin individuals from non-kin, and they were exclusively offered conspecifics that were either distantly related or non-kin, it was expected that it would not refrain from cannibalising for reasons of possible relatedness.
4. When corrected for numbers of victims eaten, survival, and juvenile development of predators fed with intra-guild prey was higher than that of cannibals. This was probably caused by a higher quality of heterospecific victims, even though conspecific victims were larger and therefore potentially contained more food. This led to the prediction that the predators should strongly prefer heterospecific prey. This was indeed borne out in independent choice experiments. Thus, the choice of predators between heterospecific and conspecific prey is not only affected by avoidance of consuming conspecifics, but also by relative prey quality.     

Predation,oviposition and conversion rates of the predacious mite,Neoseiulus californicus (McGregor) consuming different densities of Tetranychus urticae Koch,Bemisia tabaci (Genn.) and Thrips tabaci Lind.

Rates of prey consumption, egg production and prey conversion by the predacious mite, Neoseiulus californicus (McGregor) were estimated at different densities of Tetranychus urticae Koch, Bemisia tabaci (Genn.) and Thrips tabaci Lind. in the laboratory. N. californicus females functionally and numerically responded to the increasing densities of T. urticae nymphs, B. tabaci nymphs and T. tabaci larvae showing Holling’s type II. The maximum mean predation and oviposition rates by the predator females devouring T. urticae, B. tabaci and T. tabaci occurred at 15, 10 and 10 prey individuals/day, respectively, followed by the plateau levels at higher prey densities. N. californicus females exhibited the highest feeding and oviposition on T. urticae nymphs, followed by T. tabaci larvae and B. tabaci nymphs. The predator females showed the highest efficiency in converting the prey into egg progeny at 5 individuals/day of the previous prey species, respectively. T. urticae was the most favourable for N. californicus females, followed by T. tabaci and B. tabaci.     

The influence of pollen on combining predators to control Frankliniella occidentalis in ornamental chrysanthemum crops

Small scale glasshouse trials showed that second instar nymphs of Orius laevigatus reduced Frankliniella occidentalis numbers (78-92%) more than Neoseiulus cucumeris (0-30%). Combining the predators did not increase reduction of thrips numbers (84-93%). Pollen did not increase thrips control, but led to an increase in the number of thrips.     

Use of spinosad and predatory mites for the management of Frankliniella occidentalis in low tunnel‐grown strawberry

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is a major pest of strawberry. The efficacy of three species of predatory mites, Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) (both: Acari: Phytoseiidae), and Hypoaspis miles (Berlese) (Acari: Laelapidae), and their compatibility with spinosad for the control of this thrips was evaluated in commercial strawberry in spring. Low tunnel‐grown strawberry was treated with ‘water then mites’, ‘spinosad then mites’, or ‘mites then spinosad’. Predatory mites were released as single‐, two‐ and three‐species combinations. Overall, spinosad‐treated plants had fewer thrips than water‐treated plants (control). In all treatment regimes, each species of predatory mite reduced the number of thrips relative to those plants that received no mites. Predatory mites were most effective in reducing thrips when released after spinosad was applied. Any multiple‐species combination of predatory mites reduced thrips numbers more than single‐species releases. The two‐species combination of T. montdorensis (foliage inhabiting) and H. miles (soil dwelling) was the most effective in suppressing thrips. The next most effective combination was a three‐species release. Of multiple‐species combinations, the two‐species combination of T. montdorensis and N. cucumeris was the least effective in suppressing thrips numbers. The spinosad and mites only temporarily reduced the numbers of F. occidentalis. This suggests that further application of predatory mites, spinosad, or both is required to maintain F. occidentalis populations below an economically damaging level.     

Comparative life-history traits of three phytoseiid mites associated with Tetranychus urticae (Acari: Tetranychidae) colonies in clementine orchards in eastern Spain: implications for biological control

The management of Tetranychus urticae, a key pest of clementine trees, is mainly based on the use of acaricides. However, more environmentally safe measures, such as biological control, are being encouraged. Life-history traits of the three most abundant phytoseiid mites associated with T. urticae on this crop (Euseius stipulatus, Phytoseiulus persimilis and Neoseiulus californicus) were studied. The experiments were performed under laboratory conditions (25°C, 80 ± 5% RH and 16:8 h (L:D)) on clementine leaves and T. urticae as prey. Euseius stipulatus could not complete its life cycle, whereas P. persimilis and N. californicus completed it satisfactorily. The estimated intrinsic rate of increase (r _m) was significantly higher for P. persimilis (0.344 day⁻¹) than for N. californicus (0.244 day⁻¹) and both were higher than the r _m value of T. urticae on clementine leaves. Implications of these results for the biological control of T. urticae in this crop are discussed.     

Effect of pollen supplement on intraguild predatory interactions between two omnivores: The importance of spatial dynamics

Arthropods often engage in complex trophic interactions such as intraguild predation (IGP), true omnivory (i.e., feeding on plants and prey), and apparent competition. Theoretical treatments of the effects of such interactions on herbivore populations have been concerned almost entirely with equilibrium conditions. Yet these interactions are common in non-equilibrium settings such as agroecosystems, where they are likely to have a strong influence on pest populations. We therefore tested short-term effects of IGP and food supplementation on interactions between two predators (the phytoseiid mite Neoseiulus cucumeris and the anthocorid bug Orius laevigatus) and their shared prey, Frankliniella occidentalis, on strawberry plants. All three consumers feed on strawberry pollen, both mites and bugs prey on thrips, and the bug also feeds on the mites (IGP). Strong IGP on mites (IG prey) by the bugs (IG predator) was recorded in structurally-simple arenas. In a more complex setting (whole-plants), however, the intensity of IGP differed among plant structures. Likewise, pollen supplementation reduced both IGP and predation on thrips in a structurally simple setting. In the whole-plant experiment, IGP was more intense on pollen-bearing than pollen-free flowers. The study illustrated how spatial dynamics, generated when consumers track food sources differently in the habitat and possibly when herbivorous and IG prey alter their distribution to escape predation, led to site-specific configuration of interacting populations. The intensity of resulting trophic interactions was weakened by food supplementation and by increased complexity of the habitat.     

Effect of multiple mating on reproduction and longevity of the phytoseiid mite <Emphasis Type="Italic">Neoseiulus californicus</Emphasis>

Females of some insects and mites that mate repeatedly (multiple-mated females) or that have limited food supply have a shortened life span, compared to females that are allowed to mate only once (single-mated females) or that have ample food. The present study focused on the relationship between mating frequency and various reproduction-related parameters in a commercial strain (Spical) of the phytoseiid mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae). The impetus for this study came from the previous finding that single-mated females displayed an extremely long postoviposition period (ca. 60 days), accounting for more than 75% of the total adult longevity. In the present study it was found that the postoviposition period in the multiple-mated females was shorter than in the single-mated females and that longevity was gradually shortened with increasing mating frequency. Total egg production in females that mated twice or more was higher than in single-mated females, but egg production did not increase further with more than two matings. Single- and multiple-mated females ceased oviposition on the 24th and 34th day of adult life, respectively; multiple-mated females produced only male progeny on and after the 30th day. The postoviposition period of multiple-mated females was 40% shorter than that of single-mated females. Yet, the postoviposition period of the multiple-mated females is still more than 30 days, suggesting that other factors besides mating frequency have an influence on the prolonged postoviposition period. The reproductive ability of the Spical strain females gradually decreased with increasing virgin period (i.e. with increasing age), but they did not lose their reproductive potential--not even when mating was delayed for more than 2 months (i.e. females remained virgin for 70 days).     

Predatory behaviors of Neoseiulus californicus and Galendromus helveolus (Acari: Phytoseiidae) attacking Oligonychus perseae (Acari: Tetranychidae)

Predatory behaviors of Neoseiulus californicus (McGregor) and Galendromus helveolus (Chant) attacking Oligonychus perseae Tuttle, Baker and Abbatiello on avocado leaves were videotaped and analyzed. Behaviors were recorded for “fresh” predators that were used ≤ 48 hr post receipt from a commercial insectary and “cold stored” predators that were maintained at 12°C for ≈ 14 days. Fresh and cold stored G. helveolus were observed to attack O. perseae only after invading webbed nests. Conversely, fresh and cold stored N. californicus employed three different modes of predatory attack: (1) intercepting and attacking migrant O. perseae outside of web nests; (2) attacking prey through nest webbing; or (3) invading and attacking O. perseae inside nests. Predatory efficacy of both N. californicus and G. helveolus was reduced following cold storage, as both species engaged in certain predatory behaviors less frequently in comparison to predators that were not stored at low temperatures. Our observed results for N. californicus and G. helveolus attacking O. perseae are interpreted in relation to the chaetotaxy hypothesis, which proposes that phytoseiid invasion efficiency and propensity of webbed nests is facilitated by dorsal setal lengths. This revised version was published online in July 2006 with corrections to the Cover Date.