Beat sampling accuracy in estimating spruce spider mite (Acari: Tetranychidae) populations and injury on juniper

The use of a standardized beat sampling method for estimating spruce spider mite, Oligonychus ununguis (Jacobi) (Acari: Tetranychidae), densities on a widely used evergreen ornamental plant species, Juniperus chinensis variety 'Sargentii' A. Henry (Cupressaceae), was examined. There was a significant positive relationship between total spruce spider mite densities and spider mite densities from beat sampling on juniper. The slope and intercept of the relationship may be used by pest managers to predict total spider mite densities on plants from beat sample counts. Beat sampling dramatically underestimates the total number of spider mites on a foliage sample. The relationships between spruce spider mite feeding injury and spider mite density estimates from beat sampling juniper foliage and total spider mite counts on foliage were also examined. There was a significant positive relationship between spruce spider mite density as estimated from beat sampling and injury to the plants. There was a similar positive relationship between the total number of spruce spider mites and injury to the plants, suggesting that a pest manager could use beat sampling counts to estimate plant injury and related thresholds. These findings have important implications to decision-making for spruce spider mite control, especially as it relates to threshold levels and determining rates of predator releases. Further assessment of the effectiveness of beat and other sampling methods across multiple spider mite- host plant associations needs to be examined to enable pest managers to select sampling plans that are feasible and reliable.     

Control of phytoseiids in a spider mite mass-rearing system (Acari: Phytoseiidae,Tetranychidae)

Phytoseiid mites which contaminated the spider mite colony and interfered with the mass-rearing of spider mites were controlled by dipping in hot water. Immersion for 60 s in water of 50°C killed all stages ofAmblyseius fallacis (Garman),A. womersleyi Schicha andPhytoseiulus persimilis (Athias-Henriot) (Acari: Phytoseiidae). Only approximately 0.3% of theA. womersleyi eggs hatched, and this seems negligible. The populations ofTetranychus kanzawai Kishida andT. urticae (Koch) (Acari: Tetranychidae) were reduced. However, they recovered well. Although this treatment resulted in the withering of some soybean seedlings, the next trifoliate leaf to be produced was normal. A very satisfactory result was obtained when this technique was applied to the mass-rearing system.     

Biological control of the two-spotted spider mite Tetranychus urticae on strawberries by the predatory phytoseiid mite Typhlodromus pyri (Acari, Tetranychidae, Phytoseiidae)

The ‘Mikulov’ strain of the predatory mite Typhlodromus pyri Scheuten from south Moravian vineyards was released on cultivated strawberries infested with the two-spotted spider mite, Tetranychus urticae Koch. The strawberries were grown in field plantations and under glass. Typhlodromus pyri on vine shoots were successfully introduced into the field strawberry plantation but they produced no demonstrable control of the spider mites and they eventually declined in density with their prey. In contrast, T. pyri gave good control of spider mites in the glasshouse despite the occurrence of low humidity and water stress of the plants.     

Biological control of spider mites on grape by phytoseiid mites (Acari: Tetranychidae,Phytoseiidae): emphasis on regional aspects

Leaf samples were taken from 34 (1998) and 10 (1999) vineyards in five valleys in western Oregon to assess spider mite pests and biological control by predaceous phytoseiid mites. A leaf at a coordinate of every 10 m of border, 5 m into a vineyard, was taken to minimize edge effects; 20 leaves were taken at regular intervals from vineyard centers. Variables recorded at each site included grape variety and plant age, chemicals used, and vegetation next to vineyards. Sites were rated as occurring in agricultural versus riparian settings based on surrounding vegetation types. Multiple linear regressions and a computer genetic algorithm with an information content criterion were used to assess variables that may explain mite abundances. Typhlodromus pyri Scheuten was the dominant phytoseiid mite species and Tetranychus urticae Koch the dominant tetranychid mite species. High levels of T. urticae occurred when phytoseiid levels were low, and low levels of T. urticae were present when phytoseiid levels were high to moderate. T. urticae densities were higher in vineyards surrounded by agriculture, but phytoseiid levels did not differ between agricultural and riparian sites. Phytoseiids had higher densities on vineyard edges; T. urticae densities were higher in centers. Biological control success of pest mites was rated excellent in 11 of 44 vineyards, good in 27, and poor in only six sites. Predaceous mites appeared to be the principal agents regulating spider mites at low levels in sites where pesticides nontoxic to predators were used. Effects of surrounding vegetation, grape variety, growing region, and other factors on mites are discussed.     

The process of population increase and patterns of resource utilization of two spider mites,Oligonychus ununguis (Jacobi) andPanonychus citri (McGregor), under experimental conditions (Acari: Tetranychidae)

Summary Pattern of population growth and characteristics of habitat utilization and of migration by two species of spider mites were studied under experimental conditions. The population growth ofOligonychus ununguis (Jacobi) on a chestnut occurred only on a single mite-release leaf over a long period, and few individuals moved away. Most of the 2nd progeny generation females of this species emigrated from the mite-release leaf as well as the sapling by means of ballooning threads. During this growth period, population density on the mite-release leaf levelled off, whereas that on the sapling increased. In contrast, the foundress ofPanonychus citri (McGregor) on citrus actively moved over several neighbouring leaves, and until the 2nd progeny generation females emerged, individuals were distributed over all the sapling leaves by means of walking. Emigration from the sapling was not observed until the 2nd progeny females emerged, and after that the mites emigrated by means of ballooning threads. The population density ofP. citri on the sapling levelled off and was rather decreased on the mite-release leaf at the time of mite emigration. Comparing the changing pattern of the relative degree of aggregation (m ^*/m) measured in two different units between these two species, the pattern ofm ^*/m in 1 cm² on the mite release leaf inO. ununguis resembled that of the unit of leaves on the sapling inP. citri. This result as well as behavioural observations indicate that migration ofO. ununguis is the movement from leaf to leaf and that ofP. citri from sapling to sapling. It is, therefore, concluded that the boundary of the microhabitat is a single leaf forO. ununguis but sapling or foliage forP. citri. This work was presented in Annual Meeting of Jap. Soc. Appl. Ent. Zool., 1981 in Okayama.     

Life-history of predatory mites Neoseiulus californicus and Phytoseiulus persimilis (Acari: Phytoseiidae) on four spider mite species as prey, with special reference to Tetranychus evansi (Acari: Tetranychidae)

The commercially available strains of Phytoseiulus persimilis Athias-Henriot, the biological control agent of Tetranychus urticae Koch, perform poorly in the Western Mediterranean, probably because they are not well adapted to local climatic conditions. For that reason, efforts are being focused on the development of a biological control programme using native phytoseiid mites. Four species of red spider mites can be found in vegetable crops in eastern Spain: T. urticae, Tetranychus turkestani Ugarov and Nikolski, Tetranychus ludeni Zacher and the recently introduced Tetranychus evansi Baker and Pritchard. To evaluate their potential role as biological control agents, the present study evaluates the life-history of local populations of Neoseiulus californicus (McGregor) and P. persimilis when fed on T. urticae, T. turkestani, T. evansi, and T. ludeni in the laboratory. Results indicate that N. californicus and P. persimilis are able to feed and complete their development on the four tested red spider mite species. The predators may exhibit a particularly high capacity for population increase when fed on T. urticae, T. turkestani, and T. ludeni, thus may be able to provide effective control of these species in the field. When fed T. evansi, however, predator performance was poor; significant increase in development and preoviposition times, and a reduction in oviposition period and fecundity were recorded. The resultant low capacity for population growth suggests poor ability of the two tested predators to suppress T. evansi populations on commercial crops. It is unlikely therefore that P. persimilis and N. californicus, now being widely used to control T. urticae in greenhouse crops in Central Europe, will be able to halt any spread of T. evansi to greenhouse crops in temperate areas.     

Arrestment response of the predatory mite Amblyseius longispinosus to Schizotetranychus nanjingensis webnests on bamboo leaves (Acari: Phytoseiidae, Tetranychidae)

The response of the predatory mite Amblyseius longispinosus (Acari: Phytoseiidae) to the webnest of the spider mite nanjingensis (Acari: Tetranychidae) was examined using two-choice tests in the laboratory. A. longispinosus females were found significantly more often on leaves with webnests than on leaves without webnests and were often observed searching under the webbing. Because spider mites and their eggs were removed from the webnests before experiments, predators responded to stimuli associated with webbing, mite feeding damage and other residues in the webnests.     

Factors affecting location of Banks grass mite,Oligonychus pratensis (Acari: Tetranychidae), on corn leaves

The site on which adult female Banks grass mite,Oligonychus pratensis (Banks), settled when placed on corn (Zea mays L.) leaves was significantly influenced by light, leaf surface, and gravity. Mites chose the abaxial side of corn leaves when light was excluded as a factor. With a light source present, the mites went to and stayed on the leaf surface away from light. In the absence of light and leaf-surface influences, gravity showed significant effect on the choice of the under site of corn leaves by the mites; this effect also existed with light present, and acted in concert with normal light conditions (i.e., light from above). Results suggest that both heat and ultraviolet light may be responsible for the observed light effect.     

Verified and potential pathogens of predatory mites (Acari: Phytoseiidae)

Several species of phytoseiid mites (Acari: Phytoseiidae), including species of the genera Amblyseius, Galendromus, Metaseiulus, Neoseiulus, Phytoseiulus and Typhlodromus, are currently reared for biological control of various crop pests and/or as model organisms for the study of predator-prey interactions. Pathogen-free phytoseiid mites are important to obtain high efficacy in biological pest control and to get reliable data in mite research, as pathogens may affect the performance of their host or alter their reproduction and behaviour. Potential and verified pathogens have been reported for phytoseiid mites during the past 25 years. The present review provides an overview, including potential pathogens with unknown host effects (17 reports), endosymbiotic Wolbachia (seven reports), other bacteria (including Cardinium and Spiroplasma) (four reports), cases of unidentified diseases (three reports) and cases of verified pathogens (six reports). From the latter group four reports refer to Microsporidia, one to a fungus and one to a bacterium. Only five entities have been studied in detail, including Wolbachia infecting seven predatory mite species, other endosymbiotic bacteria infecting Metaseiulus (Galendromus, Typhlodromus) occidentalis (Nesbitt), the bacterium Acaricomes phytoseiuli infecting Phytoseiulus persimilis Athias-Henriot, the microsporidium Microsporidium phytoseiuli infecting P. persimilis and the microsporidium Oligosproridium occidentalis infecting M. occidentalis. In four cases (Wolbachia, A. phytoseiuli, M. phytoseiuli and O. occidentalis) an infection may be connected with fitness costs of the host. Moreover, infection is not always readily visible as no obvious gross symptoms are present. Monitoring of these entities on a routine and continuous basis should therefore get more attention, especially in commercial mass-production. Special attention should be paid to field-collected mites before introduction into the laboratory or mass rearing, and to mites that are exchanged among rearing facilities. However, at present general pathogen monitoring is not yet practical as effects of many entities are unknown. More research effort is needed concerning verified and potential pathogens of commercially reared arthropods and those used as model organisms in research.     

Population dynamics of phytophagous and predatory mites (Acari: Tetranychidae, Eriophyidae, Phytoseiidae) on bamboo plants in Fujian, China

The seasonal cycle and population dynamics of Schizotetranychus nanjingensis Ma and Yuan, Aponychus corpuzae Rimando (Tetranychidae), Aculus bambusae Kuang (Eriophyidae) and their natural enemy Typhlodromus bambusae Ehara (Phytoseiidae) were studied during 1996–1998 in moso bamboo forests in Nanping, Fujian, China. Damage to bamboo leaves was often caused by mixed populations of the three phytophagous species, which displayed different seasonal dynamics: S. nanjingensis fed actively and reproduced in May and from late July to late October (aestivating from June to mid July), Ap. corpuzae was active and reproduced from mid July to late November, and Ac. bambusae from July to next February. During Spring S. nanjingensis was the dominant species with the greatest niche width, but in Summer Ac. bambusae and Ap. corpuzae became dominant and had greater niche widths. In Autumn, Ac. bambusae decreased but both S. nanjingensis and Ap. corpuzae mites increased and the latter became dominant. In winter all species decreased sharply in number. The two spider mite species (S. nanjingensis and Ap. corpuzae) had high niche overlaps in all four seasons. Niche overlaps between the eriophyid Ac. bambusae and the two spider mites were similarly high except during the spring when Ac. bambusae was absent. The predatory mite (T. bambusae) had higher niche overlap with Ap. corpuzae than with others during Autumn and Winter, but during Spring and Summer niche overlap was higher with S. nanjingensis.     

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.     

Life tables of the predatory mite Phytoseiulus longipes feeding on Tetranychus evansi at four temperatures (Acari: Phytoseiidae, Tetranychidae)

The tomato red spider mite, Tetranychus evansi, is reported as a severe pest of tomato and other solanaceous crops from Africa, from Atlantic and Mediterranean Islands, and more recently from the south of Europe (Portugal, Spain and France). A population of the predaceous mite Phytoseiulus longipes has been recently found in Brazil in association with T. evansi. The objective of this paper was to assess the development and reproduction abilities of this strain on T. evansi under laboratory conditions at four temperatures: 15, 20, 25 and 30°C. The duration of the immature phase ranged from 3.1 to 15.4 days, at 30 and 15°C, respectively. Global immature lower thermal threshold was 12.0°C. Immature survival was high at all temperatures tested (minimum of 88% at 30°C). The intrinsic rate of increase (r _m) of P. longipes ranged from 0.091 to 0.416 female/female/day, at 15 and 30°C, respectively. P. longipes would be able to develop at a wide range of temperatures feeding on T. evansi and has the potential to control T. evansi populations.     

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.     

Different colonization patterns of phytophagous and predatory mites (Acari: Tetranychidae, Phytoseiidae) on three grape varieties: a case study

In a vineyard having three varieties of grape (Merlot, Trebbiano and Garganega) differently colonized by two phytoseiid species,Typhlodromus pyri Scheuten andAmblyseius andersoni (Chant), the dynamics of mite populations were monitored over 5 years (1989–1993) in order to study their colonization, interspecific competition and the control of spider mites, i.e.Panonychus ulmi (Koch). These aspects were also investigated by releasingT. pyri, A. andersoni andAmblyseius aberrans (Oudemans) on some of the above varieties. In most of the experimental years (1989–1992), selective pesticides were used in order to allow a successful release of phytoseiids, in particularA. aberrans. The use of non-selective insecticides was re-established during 1993 in order to test its effect on the new mite communities originating from 1989 onwards. In the first years of the experiments an apparent relationship between grape variety and phytoseiid species was observed: in the control plots,A. andersoni occurred on Merlot whereT. pyri was rare, while the latter species was largely dominant overA. andersoni on Trebbiano and Garganega.Panonychus ulmi populations reached moderate levels only on Merlot and in the first part of experiments. The variety-phytoseiid species relationship was temporary as, at the end of experiments,T. pyri was completely dominant on all varieties. This new situation started when prey occurrence and interspecific competition decreased in importance. The moderate success of theT. pyri release on Merlot contrasts with the results of previous experiments. Two factors could be involved in this phenomenon: low interspecific competition by phytoseiids and predation by macropredators.Amblyseius aberrans was able to displaceA. andersoni andT. pyri on grape varieties where the two species were more abundant and reached higher population densities on varieties with pubescent leaf undersurfaces. In the first experimental year, spider mite densities were reduced more effectively inA. aberrans release plots than in the control or inT. pyri release plots. One year later,P. ulmi reached lower levels in the release treatments than in the control.Typhlodromus pyri andA. aberrans persisted in conditions of prey scarcity. The high competitivity ofA. aberrans over the remaining two phytoseiid species constitutes a major factor in selecting predatory species for inoculative releases in vineyards.     

Life table and efficacy of Mallada desjardinsi (Chrysopidae: Neuroptera), an important predator of tea red spider mite, Oligonychus coffeae (Acari: Tetranychidae)

Green lacewing, Mallada desjardinsi Navas, is an important predator of red spider mite, Oligonychus coffeae infesting tea. Life history, life table and efficacy of M. desjardinsi were determined using red spider mite as prey under laboratory conditions. Duration of development of M. desjardinsi recorded was 5.1, 13.8 and 13 days for eggs, larvae and pupae respectively, with an average of 31.9 days from egg to adult emergence. After a mean pre oviposition period of 7.1 days, a single female laid an average of 252.6 eggs in its life time. Adult longevity of the male was recorded as 39.6 days while the females lived longer (58.2 days). The life table of M. desjardinsi was characterized by an intrinsic rate of increase (r) of 0.096 day, net reproductive rate (R ₀ ) of 153.19 eggs/female, gross reproduction rate (∑mx) of 167.28 eggs/female, generation time (T) of 52.47 days, doubling time of 7.22 days and finite rate of increase(λ) of 1.1 day. The optimum predator–prey ratios were 1:50 and 1:33 under laboratory conditions however, 1:33 and 1:25 ratios were effective in green house conditions. The results of the study can be considered as a first step towards the utilization of this predator in an IPM program for the management of red spider mite infesting tea.     

Acaricidal and biological activities of Titanium dioxide and Zinc oxide nanoparticles on the two-spotted spider mite,Tetranychus urticae Koch (Acari: Tetranychidae) and their side effects on the predatory mite,Neoseiulus californicus (Acari: Phytoseiidae)

The excessive application of pesticides raises environmental pollution levels, necessitating the need to identify alternative substances that do not cause ecological damage. In this context, the toxicity and residual efficacy of titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles (NPs) compared to abamectin against adult females of T. urticae was evaluated under laboratory and greenhouse conditions. In addition, the effects of tested NPs on the biological parameters of T. urticae as well as their side effects on the predatory mite, Neoseiulus californicus were examined. In laboratory bioassays, LC₅₀ values of TiO₂ and ZnO NPs were 5.82 and 7.09 mg L^–1, respectively, compared to 4.90 mg L^–1 in abamectin 72 hr post-treatment. TiO₂ and ZnO NPs had a prolongation effect on both the developmental and reproductive durations with mean life spans of 33.18 ± 0.72 days and 30.53 ± 0.82 days in the case of TiO₂ and ZnO NPs, respectively, compared to 24.65 ± 0.53 days in the normal case. Treated T. urticae females produced lesser fecundities (10–22 eggs less than the normal mean) and decreased hatchability rates. The highest mortality percentages in T. urticae populations were 92.4 % and 90.0 % after 24 h of spraying with TiO₂ and ZnO NPs, respectively, compared to 98.4 % in abamectin. In contrast, tested NPs demonstrated less toxicity in N. californicus populations with no phytotoxicity on treated leaves. This study is the first in Egypt to investigate the NPs control of T. urticae mites infesting cucumber plants and the effects on their biology and natural enemies.     

Effect of different ground cover management on spider mites (Acari: Tetranychidae) and their phytoseiid (Acari: Phytoseiidae) enemies in citrus orchards

We determined the effect of ground cover on phytoseiid predatory mite populations and the potential biological control of Panonychus citri (McGregor). Results showed that citrus trees with ground cover contained higher population densities of predatory mites and provided better regulation of P. citri than trees in bare soil. The ground cover Ageratum conyzoides L. performed better than Palspalum notatum Flugge in sheltering phytoseiid mites.