Is the predatory mite <Emphasis Type="Italic">Kampimodromus aberrans</Emphasis> a candidate for the control of phytophagous mites in European apple orchards?

The most important biocontrol agents of phytophagous mites (mainly Tetranychidae) in European apple orchards are the predatory mites Amblyseius andersoni, Typhlodromus pyri and Euseius finlandicus (Phytoseiidae). A similar situation is found in Trentino (north-eastern Italy), an important apple production area in Europe. Another phytoseiid mite, Kampimodromus aberrans, can be dominant in neglected fruit orchards but is rare in commercial orchards because of its susceptibility to pesticides. However, pesticide resistant strains of K. aberrans have recently been found in vineyards. In the late 1990s, one of these resistant strains was successfully released on an experimental farm in Trentino. Kampimodromus aberrans spread to an apple orchard, despite the fact that it was colonized by T. pyri, A. andersoni and E. finlandicus, and became the dominant species. Since K. aberrans’ colonization appeared to be affected by apple cultivars, experiments were conducted on potted plants of three selected apple cultivars (Golden Delicious, Red Chief, Reinette du Canada). The results stressed the effect of cultivars on apple colonization by K. aberrans and suggested the role of leaf morphology in influencing this phenomenon. Field releases of K. aberrans were successfully performed in four commercial apple orchards. The incidence of K. aberrans in the total phytoseiid population increased over time and the predator became dominant in the season following its release in two orchards. Kampimodromus aberrans persists in these orchards as the dominant species. The adaptation of K. aberrans to varying environmental conditions, its tolerance to pesticides, and its competitiveness towards other phytoseiid species suggest a potential role of this species in the biological control of phytophagous mites in European apple orchards. Handling editor: Eric Lucas.     

Predatory mites of the Phytoseiidae family in integrated and ecological pest management systems in orchards in Slovakia

During 2005–2007, 1,332 individuals of predatory mites were found in integrated and ecological orchards in Slovakia. Seven predatory mite species of the family Phytoseiidae, namely Phytoseius echinus, Phytoseiulus macropilis, Euseius finlandicus, Typhlodromus pyri, Paraseiulus triporus, Amblyseius andersoni and Neoseiulella tiliarum, were identified. Out of 1,332 individuals, 519 (39.0%) were found in the apple orchards and 813 (61.0%) in the pear orchards. Out of all predatory mite individuals, 460 (34.5%) were found in the integrated pest management system (IPM) and 872 (65.5%) in the ecological pest management system (EPM). In apple orchards, P. echinus was dominant and constituted 49.3% of the detected mites. In pear orchards, E. finlandicus was dominant and constituted 48.7% of the detected mites. Typhlodromus pyri was also abundant, especially in pear orchards. The other species were less abundant.     

Interactions among predators and phytophagous mites on apple; possible impact on biocontrol of Panonychus ulmi by Typhlodromus pyri in orchards

Laboratory experiments were conducted to determine the potential impact of the phytoseiid Euseius finlandicus, the mirid Blepharidopterus angulatus and the anthocorid Orius majusculus on the Typhlodromus pyri/Panonychus ulmi predator/prey relationship on apple. Euseius finlandicus consumed more immature spider mites than did T. pyri. When both phytoseiids were present and spider mite prey was abundant, there was no evidence of a negative interaction between the predators. In experiments where each predatory mite was confined with large numbers of the other predator, interspecific predation was exhibited by adults of each species on immatures of the other, but more so by E. finlandicus. In the predatory insect/phytoseiid experiments, when confined with spider mites and large numbers of T. pyri, both B. angulatus and O. majusculus consumed some T. pyri, but spider mites were the preferred prey. In experiments with B. angulatus, O. majusculus and T. pyri feeding on P. ulmi, there was no evidence of negative interactions between the predatory insects and T. pyri.     

Phytoseiid mites (Acari: Phytoseiidae) on apple trees and in surrounding vegetation in southern Finland. Densities and species composition

Leaf samples were collected from sprayed (n=29) and unsprayed (n=19) apple orchards, from the surrounding vegetation (n=58) and from one arboretum (n=12), altogether from 46 plant species (1–5 samples each). The density of phytoseiid mites averaged 1.2 mites/leaf on unsprayed apple trees, but only 0.06 mites/leaf on sprayed trees. The phytoseiid density exceeded 1/leaf onAesculus hippocastani, Aristolochia macrophylla, Corylus avellana, Fragaria vesca, Frxinus excelsior, Juglans cinerea, Pterocarya rhoifolia, Ribes nigrum, Rubus odoratus, Sorbus aucuparia, S. thuringiaca, Tilia×euchlora andUlmus glabra. Other common trees and bushes inhabited by phytoseiids wereCrataegus coccinea (0.2 mites/leaf),Prunus padus (0.7),Salix caprea (0.4), andTilia cordata (0.9).Twelve species of phytoseiid mites were found, of which ten occurred on unsprayed apple trees. The most widely distributed species on apple trees werePhytoseius macropilis (in 79% of unsprayed samples),Euseius finlandicus (74%),Paraseiulus soleiger (53%),Paraseiulus triporus (37%),Amblyseius canadensis (26%) andAnthoseius rhenanus (26%). The highest densities on apple trees were found in populations ofE. finlandicus (mean 0.7 mites/leaf),Ph. macropilis (0.5) andA. canadensis (0.5). On sprayed apple trees,E. finlandicus, Pa. soleiger andPh. macropilis occurred most commonly, but their mean densities were under 0.1/leaf. Almost no phytoseiids were found in orchards sprayed with oxydemetonmethyl before blooming of apple.On other plants,E. finlandicus occurred most commonly (on 33 plant species) and in the highest densities, followed byPh. macropilis (14),Pa. soleiger (12),Pa. triporus (12) andAn. rhenanus (7).Seiulus aceri andParaseiulus talbii were identified as new phytoseiid species in Finland. It is concluded that deciduous trees and bushes in forest margins around orchards can serve as important reservoirs for phytoseiid mites, and that the dominant species in these plants would migrate into and colonize the orchards if the use of harmful chemicals were restricted.     

Intra- and interspecific predation on four life stage groups by the adult females of Metaseiulus occidentalis, Typhlodromus pyri, Neoseiulus fallacis and Amblyseius andersoni

Do adult females of oligophagous species such as Neoseiulus fallacis (Garman) and Metaseiulus occidentalis (Nesbitt) show less intra- and interspecific predation on phytoseiids when other foods are scarce than polyphagous species such as Amblyseius andersoni Chant and Typhlodromus pyri Scheuten? We caged single adult females of each species without food with ten of their own eggs or larvae, with ten eggs or larvae of the other species or with ten nymphs or adult females of M. occidentalis (T. pyri for M. occidentalis). We assessed the ambulatory activity, survival time, egg levels and prey loss in each test. Polyphages (in particular T. pyri) lived longer than oligophages (in particular N. fallacis) without food. The small T. pyri detected its own stages and benefited most by feeding on small active stages of other species. Amblyseius andersoni, the largest mite, fed and gained the most of any species when held with nymphs and female adults. Metaseiulus occidentalis fed on eggs of all four species to enhance survival. The large hyperactive N. fallacis gained the least from these behaviours. Each mite seemed uniquely adapted to survive conditions of scarce prey and these behaviours may explain their roles in phytoseiid mite complexes. Overall, oligophagous adult females fed less and gained less by feeding on phytoseiids than did polyphagous adult females.     

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.     

Analysis of prey preference in phytoseiid mites by using an olfactometer,predation models and electrophoresis

Prey preference of three phytoseiid species,Typhlodromus pyri Scheuten,Amblyseius potentillae (Garman) andA. finlandicus (Oudemans) which occur in Dutch orchards, was analysed with respect to two economically important phytophagous mites, the European red spider mitePanonychus ulmi (Koch), and the apple rust miteAculus schlechtendali (Nalepa). Two types of laboratory experiments were carried out: (1) olfactometer tests to study the response when volatile kairomones of both prey species were offered simultaneously; and (2) predation tests in mixtures of the two prey species and comparison with calculated predation rates, using a model provided with parameters estimated from experiments with each prey species alone. In addition, the diet of field-collected predators was analysed using electrophoresis. For each predator species the results of the different tests were consistent, in thatT. pyri andA. potentillae preferredP. ulmi overA. schlechtendali, whereasA. finlandicus preferredA. schlechtendali overP. ulmi.     

Species diversity and seasonal dynamics of Acari on abandoned apple trees in southern Ontario,Canada

Foliage-inhabiting mites and associated insects were observed over a 3-year period on abandoned apple trees at two sites in southern Ontario. This study included species diversity and seasonal dynamics as well as the total habitat size and its seasonal fluctuations. Due to heavy feeding on the leaves in the early season by the fall cankerworm, at one observation site, the habitat available for foliage-inhabiting mites was regulated so that both the total number and the area of leaves on the tree did not increase significantly until early July. However, the influence of this on the population of the dominant mite species was minimal. The mite community was relatively stable over time. Four phytophagous species, representing a basic trophic level, were fed upon by a group of predacious mites. The phytophagous mites consisted of two rust-mite species (Diptacus gigantorhynchus sp. complex andEriophyes pyri sp. complex) and two tetranychid species (Bryobia rubrioculus andEotetranychus uncatus). On the basis of consistency in seasonal abundance,D. gigantorhynchus was the only prey species which could support the early-season population increase of the predacious mites. Ten species of predacious mites were recorded on the apple trees, nine phytoseiids and one stigmaeid; two separate species of these were common at each of two observation sites:Typhlodromus pomi and the stigmaeidZetzellia mali at one site; and two phytoseiid species,Phytoseius macropilis andAmblyseius finlandicus, at the other. There seemed to be a rather simple and stable prey/predator system at each site throughout the three seasons. Species dominance on these apple trees was investigated for the phytoseiids, especially from the perspective of the issue of one-species dominance.     

Flowers for better pest control? Effects of apple orchard groundcover management on mites (Acari), leafminers (Lepidoptera,Scitellidae), and fruit pests

Flowering companion plants provide nectar, pollen, alternative prey, shelter, and overwintering habitat for arthropod natural enemies and thus might increase their abundance and efficacy in pest control in agricultural fields. We report the results of a 6-year study on the effects of annual and perennial flowering herbs sown in alleys of an apple orchard on phytophagous and predacious mites, leafminer moths and their parasitoids and on pests causing fruit injury. Plots with weed-free bare ground and with regularly mowed grass served as controls. The abundance and diversity of predatory phytoseiid mites increased in the presence of flowering ground cover plants. However, this positive effect on phytoseiids was confined only to spring and autumn and intraguild predation (Typhlodromus pyri gradually displaced Amblyseius andersoni in the presence of flowers) also constrained their enhancement. Spider mites’ (Tetranychidae) abundance was low in all years and did not increase with the alley herb coverage. Incidence of the leafminer Leucoptera malifoliella was similar among the treatments despite the higher parasitism rate and parasitoid diversity in the plot with flowering herbs. We demonstrated that in the presence of flowering ground cover plants, the sex ratio of eulophid parasitoids' (mainly Chrysocharis pentheus) reared from L. malifoliella larvae and pupae shifted towards a male bias. Ground cover management had no effect on fruit injury caused by codling moth (Cydia pomonella) and summer fruit tortrix moth (Adoxophyes orana) and on the percentage of apples without insect damage.     

Phytoseiid Mites on Unsprayed Apple Trees in Oregon, and Other Western States (USA): Distributions, Life-Style Types and Relevance to Commercial Orchards

In unsprayed apple trees in eastern Oregon, Galendromus flumenis (Chant), Galendromus occidentalis (Nesbitt), Typhlodromus caudiglans Schuster and Metaseiulus citri (Garman and McGregor) were common phytoseiid mites; common plant-feeding mites were the eriophyid, Aculus schlechtendali Nalepa, the brown mite, Bryobia rubrioculus (Scheuten) and Eotetranychus spp.; apple rust mites seemed to be the primary prey for phytoseiids; the spider mites, Tetranychus urticae Koch and Panonychus ulmi (Koch) were scarce except for a few local outbreaks; the stigmaeid Zetzellia mali (Ewing) was at 10% of sites and its densities were inversely related to phytoseiid densities; phytoseiids were absent at some sites, particularly at high elevations where winters are severe. In seven Oregon ecoregions, G. flumenis was often at lower elevations in valleys with moderate winters; T. caudiglans was often at higher elevations; G. occidentalis was often at intermediate elevations, in young trees, and near where pesticides were used; it dominated in unsprayed trees only in almost treeless, sage-covered areas; M. citri was usually in older apple trees near agriculture. In mixed phytoseiid populations, M. citri, a generalist, and G. occidentalis, a specialist, occurred more often than expected; G. occidentalis was mostly found with T. caudiglans, a generalist; G. flumenis, a generalist, occurred less with others, possibly because it competes with both specialists and generalists. Analyses of species' distributions with multiple regression and genetic models gave explanatory r2s of 0.019-0.318. Of 29 variables, altitude of site, intensity of agricultural management, tree age, plant types, and Z. mali levels helped explain phytoseiid species presence. In the western USA, G. flumenis dominated in middle-southern latitudes; T. caudiglans dominated in the north near the Canadian border; G. occidentalis dominated in middle latitudes in parts of Washington, Idaho, Montana, and Wyoming; M. citri was at a few sites in these four states. Distributional and independent variable data were used to predict species presence at sites in Oregon with a 70% success rate. We discuss phytoseiid life-style types, community dynamics, presence in organic/conventional orchards, and trends as more selective IPM methods are used in apple orchards.     

Effects of acaricides,pyrethroids and predator distributions on populations of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> in apple orchards

We sampled mites in three apple orchards in Nova Scotia, Canada, that had been inoculated with pyrethroid-resistant Typhlodromus pyri and had a history of Tetranychus urticae outbreaks. The objective of this study was to monitor populations of T. urticae and phytoseiid predators on the ground and in trees and to track dispersal between the two habitats. Pesticides were the chief cause of differences in mite dynamics between orchards. In two orchards, application of favourably selective acaricides (abamectin, clofentezine) in 2002, coupled with predation by T. pyri in trees and Neoseiulus fallacis in ground cover, decreased high T. urticae counts and suppressed Panonychus ulmi. By 2003 phytoseiids kept the tetranychids at low levels. In a third orchard, application of pyrethroids (cypermethrin, lambda-cyhalothrin), plus an unfavourably selective acaricide (pyridaben) in 2003, suppressed phytoseiids, allowing exponential increases of T. urticae in the ground cover and in tree canopies. By 2004 however, increasing numbers of T. pyri and application of clofentezine strongly reduced densities of T. urticae in tree canopies despite high numbers crawling up from the ground cover. Another influence on T. urticae dynamics was the distribution of the phytoseiids, T. pyri and N. fallacis. When harsh pesticides were avoided, T. pyri were numerous in tree canopies. Conversely, only a few N. fallacis were found there, even when they were present in the ground cover and on tree trunks. Low numbers were sometimes due to pyrethroid applications or to scarcity of prey. Another factor was likely the abundance of T. pyri, which not only competes with N. fallacis, but also feeds on its larvae and nymphs. The scarcity of a specialist predator of spider mites in trees means that control of T. urticae largely depends on T. pyri, a generalist predator that is not particularly effective in regulating T. urticae. The Canadian Crown's right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.     

Effect of the width of the herbicide strip on mite dynamics in apple orchards

Herbicide strips are used in apple orchards to promote tree growth and survival, to increase yield and to reduce the risk of rodent damage to tree bark. However, herbicide strips, particularly wider ones, may cause problems including soil erosion, reduced organic matter, leaching of nitrates into ground water and increased incidence of plant diseases and pests, including two-spotted spider mites, Tetranychus urticae Koch. In this 2 year study we monitored mite dynamics in apple trees and used sticky bands on tree trunks to determine rates of T. urticae immigration into Nova Spy apple trees in plots with wide (2 m) or narrow (0.5 m) herbicide strips. Use of wider herbicide strips promoted two risk factors that could trigger outbreaks of tetranychid mites. First, concentrations of leaf N in apple trees were higher and those of P and K were lower with the wide strips. Such changes in nutritional quality of leaves would increase the potential for more rapid population growth of T. urticae, and to a lesser extent, the European red mite, Panonychus ulmi (Koch). Second, there were higher rates of T. urticae immigration from the ground cover vegetation into the trees. In 2006, and for most of 2007, densities of T. urticae were higher with wide herbicide strips, whereas densities of P. ulmi were not enhanced. However, by late August to early September in 2007, densities of both tetranychids were lower with wide herbicide strips. This is because both risk factors were counterbalanced, and eventually negated, by the enhanced action of phytoseiid predators, mostly Typhlodromus pyri Scheuten. From July through September 2006, ratios of phytoseiids to tetranychids were always several-fold lower with wide herbicide strips but in 2007, from mid-July onwards, predator–prey ratios were usually several-fold higher with wide strips. However, this numerical response of phytoseiids to prey density can only occur where the pesticide program in orchards is not too harsh on phytoseiids. Hence the impact of width of herbicide strip is contingent on the composition and size of the phytoseiid complex and the impact of pesticides on predation.     

Effects of humidity on eggs and immatures of Neoseiulus fallacis,Amblysieus andersoni,Metaseiulus occidentalis and Typhlodromus pyri (Phytoseiidae): implications for biological control on apple,caneberry, strawberry and hop

The lethal humidity (LH₅₀) responses at 20°C of eggs of two strains of Neoseiulus fallacis (Garman) were 71.6 and 69.7%; of three strains of Amblyseius andersoni (Chant) were 62.9, 62.0 and 62.4% and of one strain each of Typhlodromus pyri Scheuten and Metaseiulus occidentalis Nesbitt were 55.0 and 28.4%, respectively. Eggs of three genetically distinct strains of A. andersoni from Oregon, the Netherlands and Italy did not respond differently from one another nor did eggs of freely hybridizing N. fallacis from Michigan and Oregon. Mortality of larvae through development to early protonymphs at 50% RH, 20°C. was 91.9, 82.3, 46.2 and 31.0% for fed mites and 98.1, 83.2, 67.0 and 89.7% for unfed mites of Oregon strains of N. fallacis, A. andersoni, T. pyri and M. occidentalis, repectively. Fed larvae-protonymphs of M. occidentalis and T. pyri were more tolerant of low humidity than fed larvae-protonymphs of N. fallacis and A. andersoni. Mortality was less for fed than unfed larvae-protonymphs of M. occidentalis and T. pyri, but there were no differences for A. andersoni and N. fallacis. Levels of feeding by predator larvae on T. urticae and cannibalism by phytoseiid protonymphs contributed to species differences. Responses to humidity are discussed in relation to geographic and host plant distributions and biological control by single or mixed species populations of phytoseiids.     

Effects of predator-mediated apparent competition on the population dynamics of Tetranychus urticae on apples

The two spotted spider mite, Tetranychus urticae Koch, is an important herbivore pest of apple trees in Northwest China. This spider mite and another less damaging spider mite, Eotetranychus pruni Oudemans, are attacked by a common and often effective phytoseiid predator, Euseius finlandicus (Oudemans). Functional relationships were studied in the field to evaluate the impact of E. pruni and E. finlandicus on T. urticae. The results from this study showed that the predator-mediated apparent competition strongly affected the population dynamics of T. urticae. The addition of the apparent competitor E. pruni alone had little impact on T. urticae densities. Although the release of the predator E. finlandicus alone could result in reduction in T. urticae densities, the greatest reduction in T. urticae densities occurred in plots where both the predator E. finlandicus and apparent competitor E. pruni were released. In apple orchards, the early introduction of both the apparent competitor E. pruni and predator E. finlandicus would evidently increase the population size of the predator E. finlandicus and consequently significantly enhance the control of T. urticae populations. It is concluded from the study that the predator and apparent competitor release might be an appropriate control for the target species.     

Seasonal history ofTyphlodromus pyri (Acari: Mesostigmata: Phytoseiidae) in a commercial apple orchard in Czechoslovakia

The seasonal history and phenology of an indigenous field population ofTyphlodromus pyri Scheuten inhabiting a commercial apple orchard in South Bohemia are described. Data on population dynamics, number of generations, feeding, mating and reproductive habits as well as seasonal distribution within the apple tree canopy are discussed. Recommendations for mass retrieval ofT. pyri from apple orchards, their transfer to, and release in other orchards, are given. The conclusions and recommendations can be used for improving integrated pest management strategies in commercial apple orchards.     

Leaf trichomes influence predatory mite densities through dispersal behavior

Habitat complexity can mediate interactions among predators and herbivores and influences arthropod population density and community structure. The abundance of many predatory mites (Acari: Phytoseiidae) is positively associated with abundance of non‐glandular trichomes. We hypothesized that (1) increasing the complexity (trichome density mimicked with cotton fiber patches) of the habitat that predatory mites encounter on leaves would reduce adult dispersal from plants, and (2) increasing habitat complexity would reduce the time that mites spend walking. Typhlodromus pyri Scheuten retention on plants increased linearly in the presence of trichome mimics; mites placed on plants lacking leaf trichomes showed a behavioral response that led to active dispersal. Phytoseiid retention increased with both fiber patch size and fiber density within patches. Moving fiber patches from the underside of the leaf to the upper leaf surface did not change phytoseiid retention but did alter egg distribution, suggesting trichomes do not exclusively influence phytoseiid behavior. Phytoseiid activity level as measured by the amount of time spent walking did not decrease with the addition of fibers. Overall, increasing habitat complexity in the form of non‐glandular trichomes strongly reduced T. pyri dispersal behavior; the predatory mites showed a consistent preference for complex trichome‐rich habitat that was manifest both rapidly and in absence of predators. Hence, the frequently observed pattern of population‐level accumulation of phytoseiids on trichome‐rich plants appears to be driven by a behavioral response to the presence and abundance of non‐glandular trichomes on the leaf surface manifested in the level of dispersal and/or retention. The primary implication of phytoseiid–habitat interactions for biocontrol programs is that where plants have no trichomes, T. pyri will not establish. Whether this behavioral response pattern is a general response of phytoseiids to leaf trichomes or varies with species is a question that remains unanswered.     

Grape downy mildew Plasmopara viticola, an alternative food for generalist predatory mites occurring in vineyards

Generalist phytoseiids are often observed for long periods on plants in the absence of prey, feeding on alternative foods and reaching high population levels. The persistence of generalist predatory mites on plants with a scarcity or absence of prey is a requirement for successful biocontrol strategies of herbivore mites. The importance of pollen as an alternative food for the support of generalist predatory mite populations is widely recognized. However, on grape the presence of pollen is often limited and thus other food sources should contribute towards generalist predatory mite persistence on perennial plants. Previous field observations reported the relationships between the population increases of generalist phytoseiids with late-season spread of grape downy mildew (GDM) Plasmopara viticola. In this study, we test the hypothesis that GDM could be a suitable food source for the predatory mites Amblyseius andersoni and Typhlodromus pyri. In the laboratory we compared the development times, oviposition rates and life-table parameters of predatory mites feeding on pollen or GDM mycelium and spores. Grape downy mildew supported the survival, development and oviposition of T. pyri and A. andersoni. Life-table parameters showed that GDM was a less suitable food source than pollen for both phytoseiid species and that it was more favorable for A. andersoni than for T. pyri. Implications for predator–prey interactions and conservation biological control in vineyards are discussed.     

Functional response of Euseius finlandicus and Amblyseius andersoni to Panonychus ulmi on apple and peach leaves in the laboratory

The functional response of adult females of the predatory mites Euseius (Amblyseius) finlandicus and Amblyseius andersoni to larvae and adult females of the fruit tree red spider mite Panonychus ulmi was determined on apple and peach leaf disks in the laboratory at 25°C and 16:8 (L:D). For adult females of P. ulmi the predation efficiency of E. finlandicus was higher on peach than on apple, whereas that of A. andersoni was higher on apple than on peach. Efficiency of predation on larvae of P. ulmi by either predator did not differ significantly between apple and peach. On both plants, A. andersoni had a higher predation rate than E. finlandicus on larvae of P. ulmi. It is concluded that in the laboratory the host plant has a substantial effect on predation efficiency of A. andersoni and E. finlandicus when they preyed on adults but not when they preyed on larvae of P. ulmi.     

Laboratory evaluation of resistance to pesticides in the phytoseiid predator Typhlodromus pyri from English apple orchards

Typhlodromus pyri, reared on plate cultures and fed on pollen of Vicia faba, were bioassayed using a taped-slide technique. Mite stocks from isolated unsprayed orchards were used to establish base-line susceptibility to azinphos-methyl, parathion, carbaryl and permethrin. Stocks from English orchards with a spray history of organophosphates and carbaryl showed resistance of 4 to 6x to azinphos-methyl, c 50 x to parathion, >20x to carbaryl, and no resistance to permethrin. An orchard population derived from T. pyri imported from New Zealand in 1977 responded similarly. In other tests, mites exposed to spray residues on glass and on apple leaves were killed by lower concentrations than in taped-slide tests (glass < apple leaf < taped-slide technique); but for all three assay techniques the resistance factors to azinophos-methyl and carbaryl, comparing two stocks, were similar. All stocks from sprayed orchards were resistant to both azinphos-methyl and carbaryl, suggesting cross-resistance; and resistance to both these pesticides appeared to be stable in the field when selection pressure was relaxed. The results are discussed in relation to earlier work on T. pyri and two other resistant orchard-inhabiting phytoseiid species.     

Mite pests and their predators on seven vegetable crops (Arachnida: Acari)

During this study the frequency of occurrence and dominance of phytophagous and predatory mites harboring seven vegetable crops in Egypt, namely common bean, cowpea, eggplant, okra, squash, sweet pepper and sweet potato during 2017–2018 were investigated to identify predatory mites that might be useful for the biological control of the phytophagous mites. Three phytophagous and nine predatory mite species were surveyed. The two spotted spider mite Tetranychus urticae Koch of the family Tetranychidae was the dominant pest on these vegetables, while phytoseiids Phytoseiulus persimilis (Athias- Henriot), Typhlodromips swirskii (Athias- Henriot) and Euseius scutalis Chant were the dominant predators. The population of the native or indigenous phytoseiid mite fauna in Egypt such as Phytoseiulus persimilis could be considered as a good biocontrol agent and a part of the Integrated Pest Management (IPM) program in the future. Mite fauna of Egypt especially local populations of Phytoseiulus persimilis can be considered for implementation in future Integrated Pest Management (IPM).