Artificial and factitious foods support the development and reproduction of the predatory mite Amblyseius swirskii

The generalist predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was reared on Ephestia kuehniella Zeller eggs (Lepidoptera: Pyralidae), decapsulated dry cysts of the brine shrimp Artemia franciscana Kellogg (Anostraca: Artemiidae), and on meridic artificial diets (composed of honey, sucrose, tryptone, yeast extract, and egg yolk) supplemented with pupal hemolymph of the Chinese oak silkworm Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Saturniidae) (AD1), with E. kuehniella eggs (AD2) or with A. franciscana cysts (AD3). Development, reproduction and predation capacity of the predatory mites were assessed in the first (G1) and sixth generation (G6) of rearing on the different diets. Immature survival rates in G1 were similar on all diets (96.8–100 %). After six generations, however, survival of A. swirskii was significantly reduced on all diets except on A. franciscana cysts. Oviposition rates did not differ between generations when females were fed on E. kuehniella, AD2 or AD3. The total number of deposited eggs was similar among diets except in G6 where the females fed on A. franciscana cysts produced more eggs than those maintained on E. kuehniella eggs. On most diets the intrinsic rates of increase in G1 were superior to those in G6, except for predators supplied with A. franciscana cysts where no differences were observed among generations. Female mites did not lose their capacity to kill first instar Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) after six generations on the different diets, but predation rates in G6 on E. kuehniella were lower than in G1. In conclusion, the different factitious and artificial diets tested in the present study supported the development and reproduction of A. swirskii for a single generation but fitness losses occurred to a varying degree after several generations on E. kuehniella eggs or the artificial diets. Artificial diet enriched with A. franciscana cysts yielded better results than the other artificial diets. Amblyseius swirskii performed best on decapsulated Artemia cysts indicating their potential for use in the mass production of the predator or to sustain its populations in the crop after release.     

Solid artificial diets for the phytoseiid predator Amblyseius swirskii

Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is a key predator of a wide range of pests including thrips, whitefly and several mite pests. A number of artificial diets have been developed for this predator, but all of these are liquid, complicating their use in mass production. In the present study, we investigated the survival, development and reproduction of A. swirskii fed on several dry artificial diets: the tested diets were freeze dried forms of previously developed liquid meridic artificial diets supplemented with extracts of decapsulated cysts of Artemia franciscana Kellogg (Anostraca: Artemiidae) or with pupal hemolymph of Chinese oak silkworm Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Saturniidae), and newly composed powdered meridic artificial diets supplemented with ground dry A. franciscana cysts or lyophilized pupal hemolymph of A. pernyi. Performance of the mite on the artificial diets was compared with that on cattail pollen (Typha latifolia L.). Developmental time of A. swirskii females offered lyophilized diets was significantly shorter than on powdered diets. Total fecundity was significantly higher for females fed on the lyophilized diets than for those maintained on the powdered diet with A. franciscana. Daily oviposition rates were similar on T. latifolia pollen and both lyophilized diets but lower on both powdered diets. The highest intrinsic rate of increase was observed when A. swirskii was fed on T. latifolia pollen (0.210 females per female per day), followed by the freeze dried diets enriched with A. pernyi and A. franciscana (0.195 and 0.184 females per female per day, respectively), and the lowest growth rates were observed on the powdered diets supplemented with A. franciscana and A. pernyi (0.159 and 0.158 females per female per day, respectively). In conclusion, the phytoseiid was able to effectively feed on solid, powdered artificial diets. Freeze-drying of liquid diets did not influence their value to support the development and reproduction of A. swirskii. For mass rearing purposes, these dry diets have several advantages over liquid ones, including more convenient application and storage. Furthermore, they are believed to have better potential for use as supplemental foods to sustain predatory mite populations in the crop after release.     

Effect of mass rearing on the genetic diversity of the predatory mite Amblyseius swirskii

Amblyseius swirskii Athias‐Henriot (Acari: Phytoseiidae) is a predatory mite used to control whiteflies and thrips in protected crops. This biocontrol agent, originating from the Eastern Mediterranean region, has been mass‐reared for commercial use since 2005 and is widely used in augmentative biocontrol programs. As a polyphagous predator, it has to cope with different biotic and abiotic factors. However, possible adaptation to mass rearing for production might be hindering its resilience and capacity for optimum performance in the field. In this study, we investigated the effect of long‐term mass rearing on the genetic diversity of A. swirskii. We identified six microsatellite loci from whole‐genome nanopore sequencing of A. swirskii and used these in a comparative analysis of the genetic diversity and differentiation in eight wild populations collected from Israel in 2017 and a commercially available population. Our results indicate that the commercial population is 2.5× less heterozygous than the wild A. swirskii. Furthermore, the commercial population has the highest genetic differentiation from all the natural populations, as indicated by higher pairwise F_st values. Overall, we show that commercially reared A. swirskii have reduced genetic variation compared to their wild counterparts, which may reduce their performance when released to control pests in an integrated pest management (IPM) context.     

Impact of relative humidity and water availability on the life history of the predatory mite Amblyseius swirskii

The predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is currently used as an efficient biological control agent of thrips, whiteflies and spider mites, which are economically damaging pests of ornamental plants and vegetable crops grown in greenhouses and fields worldwide. Currently, the effects of relative humidity (RH) and water availability on the optimal growth of A. swirskii are unknown. Here, we test the combined effects of different levels of RH (33%, 53%, 73% and 92%) and water availability on the development and reproduction of male and female A. swirskii feeding on the dried fruit mite, Carpoglyphus lactis (Linnaeus). While eggs failed to hatch at 33% RH, the survival rates of the immature stages at?≥?53% RH increased solely in response to water availability and not due to changes in RH. Regarding growth and development, low RH extended the egg–adult duration and pre-oviposition period. We also found that the negative effects of low RH on fecundity were partially or completely eliminated when drinking water was available. For the life table parameters, the highest values of net reproductive rate (R₀) and intrinsic rate of natural increase (r) were achieved at the highest RH and when drinking water was available. Overall, water availability mitigated the negative effect of low RH on female reproduction, and female development was more sensitive to water availability than male development. Lastly, a comparison of similar research on A. swirskii suggested that water availability and RH are more influential on r than food source or temperature.

     

Sublethal effects of fenazaquin on life table parameters of the predatory mite Amblyseius swirskii (Acari: Phytoseiidae)

Knowledge of the impact of acaricides on predatory mites is crucial for integrated pest management programs. The present study evaluated the sublethal effect of fenazaquin (Pride^® 20 % SC, Behavar, Iran) on life table parameters of the subsequent generation of the predatory mite, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), fed on Tetranychus urticae Koch under laboratory conditions [26 ± 1 °C, 70 ± 3 % RH and 16:8 (L:D) h]. The sublethal concentrations including LC₁₀, LC₂₀ and LC₃₀ were determined using a dose–effect assay. The total development time of both sexes enhanced with an increase in concentration. The oviposition period and total fecundity decreased in dose-dependent manner. The intrinsic rate of increase (r) and finite rate of increase (λ) significantly descended with concentration enhancing from LC₁₀ to LC₃₀, compared with the control. The net reproductive rate (R ₀) ranged between 2.76 and 7.37 offspring. Overall, the results indicated that fenazaquin had negative effects on development and life table parameters of the subsequent generation of A. swirskii. In conclusion, fenazaquin is not a compatible acaricide with A. swirskii and should not be used with this predatory mite in integrated management of T. urticae.     

Potential predation of the exotic Amblyseius swirskii on Euseius concordis (Acari: Phytoseiidae), a predatory mite commonly found in Brazil

Intra/interspecific predation by A. swirskii.

Both Benin and Netherlands populations of Amblyseius swirskii engaged in cannibalism, and in predation on Euseius concordis larvae. Provision of pollen decreased cannibalism considerably, but had a smaller effect on predation on E. concordis. Potential effect of the eventual introduction of A. swirskii for control of Bemisia tabaci in Brazil is discussed.     

Prey suitability of western flower thrips,Frankliniella occidentalis,and onion thrips,Thrips tabaci,for the predatory mite Amblyseius swirskii

Western flower thrips, Frankliniella occidentalis, and onion thrips, Thrips tabaci, are both important polyphagous pests of vegetables and ornamentals in greenhouses. Difficulties in biological control of these pests have prompted a search for new natural enemies. Most recently, the predatory mite Amblyseius swirskii has been commercialised as biological control agent of whiteflies and thrips. However, little is known about the suitability of thrips as prey for A. swirskii. We therefore assessed prey acceptance and life history of A. swirskii when feeding on F. occidentalis and T. tabaci at 25±1°C. Amblyseius swirskii juveniles preyed upon first larval instars of both F. occidentalis and T. tabaci but suffered from high mortality (67 and 78%). Developmental time (egg to adult) of A. swirskii was 7.8 days with either prey species. Adult A. swirskii females readily accepted first larval instars of both thrips species, which were attacked in <20 min on a leaf and <10 min in an artificial cage. Oviposition rates (0.92 and 0.99 eggs/female/day) and offspring sex ratios (63 and 70% females) were similar with F. occidentalis and T. tabaci as prey. Less than one-third of juveniles reaching adulthood and oviposition rates below one egg/female per day resulted in relatively low intrinsic rates of increase (r _m) (0.056 and 0.024 per day with F. occidentalis and T. tabaci, respectively). Altogether, our study suggests that the recently reported superiority of A. swirskii to the widely used Neoseiulus cucumeris in suppression of thrips is due to other traits than its population growth capacity with thrips as prey.     

Life history and demography of the predatory mite,Amblyseius longispinosus Evans

The life history and demography of Amblyseius longispinosus Evans were studied under laboratory conditions 25–28°C and 65–85% RH using the red form of the twospotted spider mite, Tetranychus urticae Koch complex as prey. The entire development from egg to adult averaged 102.5 h for both sexes with a survival rate of 90.0%. Immature females consumed more prey eggs than males, averaging 7.9 and 6.4 eggs/day, respectively. The embryonic development time for male eggs was longer (average 45.2 h) than for female eggs (average 42.6 h). The average duration of succeeding stages did not differ between the sexes: larva, 15.7; protonymph, 21.1; and deutonymph, 23.0 h. Larvae were not observed to feed. Statistically significant differences between sexes were noted with respect to consumption of the deutonymphs (female, average 4.0±0.2; male, average 2.9±0.3 eggs/day) but not of the protonymphs. Mating occurred on the same day as adult emergence and was repeated several times during the reproductive life. Egg laying started on the second day after emergence. Parameters relating to oviposition were: fecundity, gross (50.7) and net (43.3) eggs/female; hatchability, 99.6% (gross) and 99.5% (net); the oviposition lasted at most 28 days and showed a peak in the first week. Net reproductive rate (R₀) was 36.7 female offspring/female/generation time (T) of 9.0 days. The sex ratio was biased toward the females (71.9%), while the intrinsic rate of increase (r_m) was 0.4 with a doubling time (DT) of 1.7 days. Males lived longer (36 days) than females (30 days) with a LT₅₀ for males of 26 days and for females of 22 days.     

山楂叶螨对胡瓜钝绥螨的吸引作用研究

采用两侧吸引作用试验测定天敌胡瓜钝绥螨Amblyseius cucumeris Oudemans在田间对山楂叶螨的搜索和控制能力。结果表明：山楂叶螨不同螨态对胡瓜钝绥螨均有显著的吸引作用,排泄物对胡瓜钝绥螨没有明显的吸引作用。山楂叶螨对胡瓜钝绥螨的这种吸引作用说明胡瓜钝绥螨在田间具有自动搜索山楂叶螨的能力,可用于山楂叶螨的生物防治。     

Photoperiodism and thermoperiodism in the predatory mite Amblyseius potentillae are probably based on the same mechanism

Summary A comparative study was made of the photoperiodic and thermoperiodic induction of diapause in the phytoseiid mite Amblyseius potentillae. Sensitivity to thermoperiod was found to be highest during the protonymphal and deutonymphal stages, with some sensitivity still being present in the young adult. Summation of both photoperiodic and thermoperiodic cycles was shown to take place, which demonstrated the presence of a photoperiodic counter as well as a thermoperiodic counter in these mites. Vitamin A appeared to be necessary for some early step in the physiological mechanism of diapause induction and not just for the expression of the diapause response. The light sensitivity threshold for photoperiodic induction of diapause was found to be extremely low, viz. less than 0.02 W/cm². Moreover, the light sensitivity threshold appeared to be strongly temperature dependent in A. potentillae. Experiments in which the mites experienced various sequences of short-day photoperiods and short-day thermoperiods, applied either concurrently or in succession, showed that the information collected by the photoperiodic counter and the thermoperiodic counter is integrated into one induction sum. These results strongly suggest that photoperiodic and thermoperiodic induction of diapause in these mites is based on the same physiological mechanism.Abbreviations DD continuous darkness - LL continuous light - LD light-dark cycle (e.g. LD 16:8 is a cycle of 16 h of light and 8 h of darkness) - TC thermoperiodic cycle (e.g. TC 16:8 (27°: 15°) is a thermoperiod with a 16 h thermophase of 27 °C and an 18 h cryophase of 15°C)     

Beneficial effect of supplementing an artificial diet for Amblyseius swirskii with Hermetia illucens haemolymph

Artificial diets have been developed to sustain the mass rearing of a wide range of arthropod natural enemies, with varying success. In some cases, such diets can be optimized using insect‐derived materials, such as haemolymph. In this study, we examined the effect of supplementing haemolymph of the black soldier fly, Hermetia illucens, to a basic artificial diet for the phytoseiid mite Amblyseius swirskii. The survival, development and reproduction of the predatory mite were assessed when fed on artificial diets composed of honey, sucrose, tryptone, yeast extract and egg yolk, supplemented with 5%, 10%, or 20% of H. illucens pre‐pupal haemolymph. Developmental time from larva to adult was shorter for males and females offered artificial diets supplemented with 20% haemolymph vs. the basic diet. The oviposition rate and total fecundity of females reared on the basic diet were substantially lower than those of females supplied with the enriched diets. The intrinsic rate of increase was highest on the diet containing 20% haemolymph, followed by those containing 10% and 5% haemolymph. In a subsequent diet‐switching experiment, mites fed on the basic diet in their juvenile stages were switched upon adulthood to diet enriched with different concentrations of H. illucens haemolymph. The females that were fed with the enriched diets from the adult stage on had higher oviposition rates and fecundities than those maintained on the basic diet, but their reproductive parameters were not significantly affected by the concentration of the haemolymph in the artificial diet. In conclusion, supplementing artificial diets with black soldier fly haemolymph significantly improved their nutritional value for A. swirskii. Our findings indicate the potential of using H. illucens as a cheap source for haemolymph in artificial diets, as the fly can be cost‐effectively produced at a large scale on organic waste materials.     

Prey preference of predatory mite Amblyseius swirskii (Acari: Phytoseiidae) on Tetranychus urticae (Acari: Tetranychidae) and Bemisia tabaci (Hemiptera: Aleyrodidae)

Tetranychus urticae Koch (Acari: Tetranychidae) and Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) are major pests in greenhouse crops. Recently, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was shown to be an effective biological control agent of both pests. Therefore, the prey preference of A. swirskii was determined using immature stages of T. urticae and B. tabaci in three various treatments based on Manly's β preference index (β). These treatments consisted of immature stages of two prey species (egg, first and second instar nymphs) with densities 12:12, 6:6 and 3:3, respectively, and with 13 replicates. After 24?h starvation, same-aged females of A. swirskii were added to the leaf discs. All experiments were done on bean leaf discs in Petri dishes (8?cm in diameter) in laboratory conditions with 25?±?2°C, 70?±?5% relative humidity and the photoperiod of 16L:8D hours. Comparing the preference indices using t-tests indicates a significant preference of the predator on eggs (t?=?10.80, df?=?24, P?t?=?8.17, df?=?24, P?T. urticae than B. tabaci. Our findings suggest that developmental stages of prey have effect on the prey selection by A. swirskii.     

Amblyseius andersoni Chant (Acari: Phytoseiidae), a successful predatory mite on Rosa spp

Roses on commercial nurseries commonly suffer from attacks by the two-spotted spider mite, Tetranychus urticae, which have a negative influence on growth and quality. The aim of this project is to find natural enemies that are well adapted to roses, and may improve biological control. At different sites such as a plant collection garden, public parks and field boundaries, leaves were sampled from roses to identify the indigenous species of predatory mites. Amblyseius andersoni was amongst other species frequently found, which suggests that this species thrives well on roses. The possibility for biological control of spider mites with A. andersoni was investigated both in container roses outdoors and in glasshouses. In plots of outdoor roses artificially infested with spider mites, the following treatments were carried out: spider mites alone (untreated plot), Amblyseius andersoni Amblyseius andersoni and ice plants, Neoseiulus californicus, Neoseiulus californicus and ice plants. There were four replications of the treatments. The ice plants, Delosperma cooperi, were added to some treatments to supply pollen as extra food for the predatory mites. Natural enemies such as Chrysoperla spp., Conwentzia sp., Orius sp., Stethorus punctillum, and Feltiella acarisuga occurred naturally and contributed to the control of spider mites. After one month the spider mites were eradicated in all treatments. At the end of the trial, predatory mites were collected from all plots for identification. The ratio of Amblyseius andersoni to Neoseiulus californicus was approximately 9:1. There was no obvious effect of the ice plants on the number of predatory mites. On a nursery, where new roses are bred and selected, Amblyseius andersoni was released in three glasshouses after one early treatment with bifenazate against two-spotted spider mite Tetranychus urticae. In two of these glasshouses Neoseiulus californicus was also released. Samples, which were taken in the summer months showed that the spider mites were kept at a very low level. Amblyseius andersoni was found, even if spider mites were absent. Rose plants infested with spider mites, that were brought in to the glasshouses later developed spider mite 'hotspots'. Phytoseiulus persimilis was introduced in the hot spots and contributed to the control along with Neoseiulus californicus, Amblyseius andersoni and naturally occurring Feltiella acarisuga. These observations showed that Amblyseius andersoni is a good candidate for preventing spider mite outbreaks, as it easily survives without spider mites. This predatory mite is able to survive on other food, including thrips and fungal spores.     

Biology and feeding behaviour of the predatory mite,Amblyseius Brazilli [Mesostigmata: Phytoseiidae]

The predator passes through the larval, protonymphal, deutonymphal and adult stages. The life cycle from egg to adult was about 7 days for both sexes. The adult female longevity was 30 days. The adult stage consumed more prey than other stages. The number of eggs deposited per day increased when fed on pollen or mite with pollen, and the developmental period was shorter. The mite could develop on royal jelly but took a longer period and deposited half the number of eggs deposited on pollen or prey. Honey was insufficient to induce development or a high rate of reproduction. A combination of royal jelly and honey encouraged development, oviposition and survival.

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Résumé Le prédateur passe par quatre stades: la larve, la protonymphe, la deutonymphe et l'adulte. Le cycle de vie de l'œuf à l'adulte est de 7 jours pour les deux sexes. La longévité de la femelle adulte est de 30 jours. La consommation de proies de l'adulte excède celle des autres stades. Le nombre d'œufs déposés par jour augmente dans le cas de l'élevage sur pollen ou sur tétranyques plus pollen, et la période de développement est plus courte. L'acarien peut se développer sur la gelée royale mais plus lentement et dépose la moitié du nombre d'œufs obtenus dans le cas du pollen ou de proies. Le miel est insuffisant pour le développement et la reproduction. Un mélange de gelée royale et de miel améliore le développement, l'oviposition et la survie.

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This work was conducted as part of a programme of research on the predacious mites of Brazil, under support of a National Research Council grant to Dr.E. M. El-Banhawy     

Intraguild predation among the predatory mites Amblyseius eharai,Amblyseius cucumeris and Amblyseius barkeri

Predator species with the same prey interact not only by competition for food and space but also by intraguild predation (IGP). The impact of IGP on introduced phytoseiid mites and native species in the context of biological control is a matter of considerable debate. Amblyseius eharai is the dominant native citrus species in central China, while Amblyseius cucumeris and Amblyseius barkeri are candidates for importation. All three species can feed on the spider mite Panonychus citri, which is the main pest in citrus. This study investigated, in the laboratory, possible IGP among these species in the absence and presence of P. citri, respectively. IGP in different densities of shared prey and intraguild (IG) prey was also studied. All three species consumed heterospecific larvae and eggs but not adults, and the IGP rate of larvae was significantly higher than that of eggs in the absence of shared prey. Additionally, the IGP rate of each group was reduced dramatically in the presence of both shared and IG prey when compared to the absence of shared prey. This occurs most likely because the three species prefer to feed on their natural prey P. citri, rather than on IG prey. Our results showed that A. eharai seems to be a more voracious IG predator than A. cucumeris. A. eharai was much more prone to IGP than A. barkeri.