Predatory mirids of the green apple aphidAphis pomi,the two-spotted spider miteTetranychus urticae and the European red mitePanonychus ULMI in apple orchards in Québec

The incidence of predation of eight species of predacious mirids (Hemiptera: Miridae) present in an apple orchard of Québec on the green apple aphid, two-spotted spider mite and European red mite were investigated. The daily consumption rates varied from 1–2 green apple aphids forHyaliodes vitripennis Say andCampylomma verbasci Meyer to 7–9 aphids forDeraeocoris fasciolus Knight andLepidopsallus minisculus Knight.H. vitripennis consumed significantly more mites than the other mirid species with 26 and 18 mites per day for the two-spotted spider mite and the European red mite respectively. The combined use ofH. vitripennis andL. minisculus is suggested for the control of phytophagous mites. This paper is contribution No. 335/91.06.02R, Research Station, Agriculture Canada, Saint-Jean-sur-Richelieu, Québec, Canada.     

Die Feinde der Raubmilben als Reduzierender Faktor der Spinnmilben

Summary The relations betweenMetatetranychus ulmi living on apple trees and its different predators are complex. The most important natural enemy of this spider mite is the predacious miteTyphlodromus pyri (= T. tiliae). It destroys more spider mites than the beneficial insects do. In the district of Stuttgart-Hohenheim about 38 species of insects and spiders feed onTyphlodromus mites. For instanceT. pyri is reduced considerably byOrius minutus. This bug is a natural enemy of aphids and spider mites, however it prefers the predatory mites. It attacks the spider mites and aphids only ifTyphlodromus mites are not available.Chrysopa vulgaris andAnthocoris nemorum are similar in their feeding habits. These two destroyTyphlodromus pyri also but they are less important thanO. minutus. The other beneficial insects in our orchards have little effect on spider mites or predacious mites. If we have enough pests on our apple trees to make spraying necessary, we should look forTyphlodromus mites and be careful no to destroy them. We should always examine the composition of the biocoenosis applying chemical agents because the populations of insects and predacious mites may vary from one area to the other.      

The effect of pyrethroid lambdacyhalothrin applications on the spatial distribution of phytophagous and predatory mites in apple orchards

The spatial distribution of three phytophagous mites,Panonychus ulmi (Koch),Tetranychus urticae Koch andAculus schlechtendali (Nalepa), and two predacious mites,Zetzellia mali (Ewing) andAmblyseius fallacis (Garman), and the effect of pyrethroid lambdacyhalothrin applications on mite spatial dispersion were investigated over a 3-year period in an apple orchard in Ontario. The index of dispersion and the slope of Taylor's power law were used to evaluate dispersion patterns of mites. Panonychus ulmi showed that between-tree spatial variation decreased with an increase of population densities, whereas between-leaf variation increased with population densities. With all other four species it appeared that between-tree variation is much greater than between-leaf variation at all field population density levels. The values ofb by Taylor's power law suggested that all five species of mites are aggregated, but that in generalP. ulmi andT. urticae (b=1.427–1.872) are more aggregated than their predators (b=1.254–1.393). Taylor's regression technique suggests that pyrethroid applications causedP. ulmi, T. urticae, Z. mali andA. fallacis to be less aggregated whileA. schlechtendali was more aggregated. The impact of changes in mite spatial distribution following pyrethroid applications on sampling plans is discussed.     

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.     

Laboratory studies on the feeding habits,reproduction and development of three phytoseiid species,Typhlodromus pomi,Phytoseius macropilis andAmblyseius finlandicus (Acari: Phytoseiidae), occurring on abandoned apple trees in Ontario,Canada

Laboratory studies on predation, reproduction and development were conducted on three phytoseiid species,Typhlodromus pomi (Parrott),Phytoseius macropilis (Banks) andAmblyseius finlandicus (Oudemans). These species were dominant phytoseiid mites on the abandoned apple trees with which ecological experiments were carried out in southern Ontario, Canada. Throught the studies, a rust mite species (Diptacus gigantorhynchus sp. complex), a single consistent prey in the orchard, was used as food. Results showed that the three predators developed well with the rust mites as food, and thatA. finlandicus developed most rapidly and had the highest predation rate. However, this species showed a poor tolerance to low prey densities. These observations suggest that this species is a predacious species and the other two species were more or less general feeders. All species showed the same pre-mating behaviour (Amblyseius-Typhlodromus type), but they exhibited a variety of mating and oviposition behaviours.     

Phytophagous and predaceous mites associated with vegetable crops from Riyadh,Saudi Arabia

This study was conducted to investigate phytophagous and predatory mites associated with vegetable plants in Riyadh, Saudi Arabia. Eight phytophagous and 10 predacious mites were collected from 14 species of vegetable crops covering five major production localities. Out of these 18 mite species, 13 species are new to the mite fauna of Saudi Arabia. In addition, the two species, Tenuipalpus punicae and Agistemus exsertus, are reported for the first time on vegetable crops in Saudi Arabia. For each mite species found, notes on host plant association and occurrence period are given. An illustrated key for the identification of the 18 mite species reported in this study is provided and this can be used to improve the IPM programs by applying the local natural predatory mites in controlling mite pests in Saudi Arabia.     

Abundance of phytoseiid mites on Vitis species: effects of leaf hairs,domatia, prey abundance and plant phylogeny

We observed the number of predatory mites (Phytoseiidae:Typhlodromus caudiglans) on the foliage of 20 North American species of grapes (Vitis spp) plus the domesticated EuropeanVitis vinifera, all grown in a common garden. We found relatively few phytophagous mites. The numbers of phytophagous mites were not correlated with the plant characteristics that we measured. We found approximately five times as many predatory mites as phytophagous mites and the numbers of these phytoseiid predators were not affected by the availability of prey. Similarly, numbers of phytoseiids were unaffected by plant gender and, hence, the availability of pollen, another source of food. The numbers of phytoseiids were not clustered according to the taxonomic grouping of the tested plant species. Leaf surface characteristics explained over 25% of the variance in the numbers of phytoseiids. Numbers of phytoseiids were positively associated with the density of vein hairs, the density of bristles in leaf axils, and the presence of leaf domatia. These results suggest that sheltered habitats rather than food availability may limit the numbers of phytoseiid mites on grapevines.     

Euseius addoensis addoensis,an effective predator of citrus thrips,Scirtothrips aurantii,in the eastern Cape Province of South Africa

The predacious mite,Euseius addoensis addoensis (McMurtry) (Acari: Phytoseiidae), significantly (P<0.05) reduced scarring on Palmer Navel oranges,Citrus sinensis (L.) Osbeck, caused by the citrus thrips,Scirtothrips aurantii Faure (Thysanoptera: Thripidae). A chemical exclusion method employing dicofol was used to determine the effect of the predator and numbers ofS. aurantii were monitored on sticky yellow traps. At two sites where numbers of citrus thrips and predacious mites were high, the percentage fruit culled from export quality due to damage byS. aurantii was reduced from 25.5 to 15.5% and from 32.7 to 18.7% by predacious mite activity.Euseius a. addoensis sometimes prevented damage from exceeding 1% cull and was most effective when mean numbers exceeded one mite per inside leaf at petal fall. The best correlation between numbers of mites and the percentage fruit culled at harvest was –0.96 at the location with the highest number of citrus thrips. Tartar emetic (0.398% a.i.) plus sugar (0.4% a.i.) treatments for citrus thrips were slightly detrimental toE. a. addoensis populations but their numbers soon recovered. An alternative treatment, methiocarb 0.016% a.i. plus sugar (0.4% a.i.), almost eliminated the predacious mites and resulted in more citrus thrips damage (10.7% cull) than in the adjacent untreated control (0.2% cull) which contained predacious mites.     

Emission of volatile organic compounds by apple trees under spider mite attack and attraction of predatory mites

Emission rates of volatile organic compounds (VOCs) from Pirus malus L. subsp. mitis (Wallr.) var. Golden Delicious and var. Starking attacked by the phytophagous mite Panonychus ulmi Koch, and their attractiveness to the predatory mites Amblyseius andersoni Chant and Amblyseius californicus McGregor, were studied during three years. A large variability was found in the emission of individual VOCs depending on the infestation, the apple tree variety and the date. There were larger total VOC emission rates and larger total VOC leaf concentrations in apple trees attacked by phytophagous mites, especially in the var. Starking. In infested trees of this variety, there were also more predatory mites. An olfactometer assay showed that predatory mites preferentially chose branches infested by Panonychus ulmi (85% went to infested branches vs 15% to uninfested control branches) indicating that volatiles may be used as cues to find their prey.     

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).     

Stigmaeid-phytoseiid interactions and the impact of natural enemy complexes on plant-inhabiting mites

Interactions within the natural enemy complex of plant-inhabiting mites are of practical interest. There are frequently several predatory mite species present or available for introduction and it is difficult to tell whether a single species or combination of species should provide the most effective means of biological control. We used a simulation model to examine the interactions between predatory mites of two families, the Stigmaeidae and Phytoseiidae, representatives of which feed on phytophagous apple mites. To identify key differences in predatory behavior and life history, various stigmaeid parameters were substituted with those of phytoseiids, and changes in the efficacy of either stigmaeids alone or in combination with phytoseiids were evaluated graphically. At low prey densities stigmaeids held an advantage over phytoseiids in terms of efficacy because of their higher preference for prey eggs, higher oviposition relative to prey consumption and the ability to consume their own eggs, while at high prey densities the higher maximum predation rate of phytoseiids gave them a higher efficacy. Thus the weaker predator (the stigmaeid) is the more effective competitor at low prey densities. The model did not account for dispersal, but since stigmaeids are the weaker dispersers, the possibility of developing stability in this system is much greater than if phytoseiids were the better competitors. A combination of stigmaeids and phytoseiids was shown to have greater efficacy than either predator alone over a wide range of prey densities.     

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.     

Bionomics ofEotetranychus tiliarium and its phytoseiid predators

Under urban conditions,Eotetranychus tiliarium (Hermann) frequently develops into high population densities onTilia lining streets, in contrast to its development in natural habitats and on park trees. In mixed forest and on park trees, a regulating system precludes these outbreaks. In an earlier study it was shown that a change in the predacious mite species composition, leading to displacement of the most effective predator species by less effective ones, is the main reason for this phenomenon.The bionomics ofE. tiliarium on its host plantTilia spp. in various habitats were studied as well as the characteristics of the predacious mites which determine their potential for preventing spider-mite outbreaks.Predacious mites from the family Phytoseiidae were able to preventE. tiliarium outbreaks.Paraseiulus soleiger was the most effective predacious mite species, because it has a short development period, a long period of longevity, a long oviposition period, and has a clear preference forE. tiliarium and a high prey-consumption capacity. Eotetranychus tiliarium onTilia lining streets has a greater potential for increase than the spider mites from park trees and from forest trees. The nutritive value of leaves on trees in street habitats is increased by the increased salt content in the soil from snow control in winter. Also, the higher temperatures in urban conditions may stimulate population development.     

Studies of the growth, development and reproductive performance of the aphid shape Myzus persicae on artificial diets containing potato glycoalkaloids

Using data sets of phytophagous and predaceous mites, we introduce a method for estimating standard error bands for the proportion of habitat occupied by a species as a function of mean density, by transforming error bands from the variance-mean power law. Error bands produced by this method were more conservative than bands produced by bootstrapping and repeated subsampling methods applied to the same data. Though conservative, the binomial model showed potential to be an easily interpreted, powerful method for detecting differences in the proportion of habitat occupied among data sets (interpreted as differences in species aggregation) on one spatial scale. This was demonstrated in three specific cases: between years for the predaceous mite Typhlodromus pyri Scheuten (Acari: Phytoseiidae) on Red Delicious apple trees (Malus pumila Miller), for the phytophagous mite Tetranychus urticae (Koch) (Acari: Tetranychidae), whether or not it was preyed upon by the predaceous mite Neoseiulus fallacis (Garman) (Acari: Phytoseiidae) on hops (Humulus lupulus L.), and among individual life stages of the predaceous mite Metaseiulus occidentalis (Nesbitt) (Acari: Phytoseiidae) on apple.     

Does dust result in mite outbreaks in apple orchards?

The effect of dust on phytophagous mite numbers was examined in five apple orchards situated in the dry, inland apple producing Ceres area, South Africa. The study was conducted over three seasons. The season with the most dust had the least number of mites. There was no relationship between the amount of dust on leaves and mite numbers from different orchards. Of the 15 correlations between the amount of dust on individual trees and the number of mites on these trees, two were marginally not significant and one was highly significant, but negative. Therefore, seasons during which there is a lot of dust did not result in mite outbreaks nor did dusty orchards harbour elevated mite population levels, and trees with a lot of dust did not necessarily harbour more mites than trees with less dust. However, if there is enough dust to cause stress to the trees, phytophagous mite outbreaks could occur.     

Field Releases of the Predatory Mite Neoseiulus fallacis (Acari: Phytoseiidae) in Canada, Monitored by Pyrethroid Resistance and Allozyme Markers

The predacious phytoseiid mite Neoseiulus fallacis (Garman) is an important agent for the biological control of spider mites in deciduous fruit orchards in North America and Canada. It would be helpful to monitor the fate of released individuals to improve the results of introductions of the predators in biological control trials. We have used two types of genetic markers, pyrethroid resistance and allozymes, for indirect estimation of the survival of N. fallacis introduced in an apple orchard in Ontario, Canada. Mite samples were submitted to toxicological tests. The polymorphism of four enzymes was studied in individual females using an isoelectric focusing technique. A mite sample was taken from the field, mass-reared in the laboratory, and selected for permethrin resistance. This strain was released on several apple trees treated with permethrin, and mite samples were collected from the same trees 10 to 90 days later. The genetic composition and the insecticide resistance level of this sample were compared to those of two other samples from trees where mites had not previously been released, either in the same orchard or in a neighboring block. A control susceptible strain was compared using mites collected earlier from trees on the same site but outside the present experiment. The mites collected from the release trees and those from the strain used for the releases were found to be genetically closely related, as judged from a small genetic distance, and from similar levels of insecticide resistance in both samples. The control samples from the nonrelease trees were genetically distant from these and displayed low resistance levels. These results indicate that the released genotypes established and persisted in the release trees for the period of the experiment. The utility of the two approaches in assessing the fate of released natural enemies is discussed.     

Two predatory mite species as potential control agents of broad mites

The broad mite is a key pest of various crops worldwide, including chili pepper (Capsicum frutescens), where it is controlled with chemical pesticides. Two phytoseiid predators (Amblyseius herbicolus and Neoseiulus barkeri) and a blattisociid mite species (Lasioseius floridensis) occur in association with the broad mite in Brazil. Predation of broad mites and oviposition rates of A. herbicolus were higher than those of N. barkeri and lowest for L. floridensis. On intact plants, both phytoseiids controlled broad mite populations seven days after their release. In a separate experiment, the predators controlled broad mites on flowering plants during 15 days. After two months, plants with predators produced heavier fruits than plants without predators. Concluding, these two phytoseiid species can control broad mites on chili peppers plants at different densities and over time, reducing production losses, and should be evaluated under field conditions.     

Agroforestry management and phytoseiid communities in vineyards in the South of France

This study deals with the long-term effect of agroforestry management (trees within vine crops) on communities of phytoseiid mites. Several plots were considered: vineyards co-planted with Sorbus domestica or Pinus pinea, monocultures of vines and monocultures of S. domestica or P. pinea. All vine plots included two vine cultivars, Syrah and Grenache. Phytoseiid mites have been surveyed in these plots during several years within the previous 10 years. In 2010, samplings were again carried out in these same plots, from May to September, twice a month. Significantly higher densities of Phytoseiidae were observed on the cultivar Syrah (0.85 phytoseiids per leaf) than on Grenache (0.26 phytoseiids per leaf). Furthermore, significantly higher phytoseiid mite densities were observed in the monocultural grapevine plot than in the two co-planted ones. The main species found was Typhlodromus (Typhlodromus) exhilaratus in all vine plots considered. However, Kampimodromus aberrans was observed in the grapevine plots co-planted with the two trees, but never in the monocultural vine plot. Surprisingly, this phytoseiid species was not found on the co-planted trees, nor in the neighbouring uncultivated vegetation. Several hypotheses are discussed to explain such an unexpected distribution. Furthermore, contrary to what has been observed previously, agroforestry management did not seem to favour phytoseiid mite development, especially on the Grenache cultivar. Again, some hypotheses are developed to explain such observations and density modifications.     

Mite populations on grapevines in south-eastern Australia: Implications for biological control of grapevine mites (Acarina: Tenuipalpidae,Eriophyidae)

Pest and predatory mite populations were monitored over a 2 year period on grapevines in three viticultural regions of southern Australia (The Riverlands, Sunraysia and Murrumbidgee Irrigation Area [MIA]). The mite pestsBrevipalpus spp..Colomerus vitis (Pagenstecher) andCalepitrimerus vitis (Nalepa) occurred in each region with a predatory mite fauna which showed considerable interregional variation in incidence, abundance and composition. Nine species of Phytoseiidae, the dominant predatory mite family, were recorded inhabiting grapevines. In the Riverlands, mite populations were apparently suppressed by two phytoseiids (Typhlodromus doreenae Schicha,Amblyseius victoriensis (Womersley)) in vineyards on which no insecticide was used and on which sulphur and copper were used to control vine diseases. In Sunraysia and MIA, vineyards which generally had greater inputs of synthetic pesticides, particularly fungicides, five to eight phytoseiid species were recorded. However, they were less abundant and appeared to have less impact on mite (particularlyBrevipalpus spp.) populations. The population dynamics of pest and predatory mites on grapevines in southern Australia and implications for mite management based on biological control are discussed with respect to pesticide (particularly fungicide) inputs and phytoseiid biology/ecology.     

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.