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.     

Influence of diet on life table parameters of <Emphasis Type="Italic">Iphiseius degenerans</Emphasis> (Acari: Phytoseiidae)

Studies on the reproduction, longevity and life table parameters of Iphiseius degenerans (Berlese) were carried out under laboratory conditions of 25 ± 1 °C, 75 ± 5% RH and 16L:8D h. As food sources for the predatory mite, Ricinus communis L. pollen, all stages of the spider mite Tetranychus urticae Koch, Frankliniella occidentalis (Pergande) larvae, and Ephestia kuehniella Zeller eggs were selected. All diets were accepted as food by the adult mites. Female longevity ranged from 29.5 to 42.4 days, the highest value was recorded on a diet of Ephestia eggs. The highest percentage of females escaping the experimental arena was observed on the diet consisting of thrips larvae. The highest oviposition rate (1.9 eggs/female.day) was recorded when the predator was fed on spider mites on an artificial substrate. For other diets, oviposition rates ranged from 1.0 to 1.3 eggs/female.day. The intrinsic rate of natural increase (r _m) of I. degenerans varied between 0.015 and 0.142 females/female.day. The diet consisting of castor bean pollen resulted in the highest population growth whereas the diet on spider mites brushed off onto a bean leaf arena resulted in the slowest population growth. This can be explained by the inability of the predator to cope with the webbing of T. urticae, and the high escape rate of the progeny when reared on spider mites. The percentage of females in the offspring ranged from 40 to 73%.This revised version was published online in May 2005 with a corrected cover date.     

Effect of pollen,natural prey and factitious prey on the development of <Emphasis Type="Italic">Iphiseius degenerans</Emphasis>

The predatory mite Iphiseius degenerans (Berlese) is commercially available as a biological control agent of thrips and spider mites in greenhouse crops. Developmental duration and immature survival of I. degeneransreared on nine types of food (almond pollen, apple pollen, castor bean pollen, plum pollen, sweet pepper pollen, Tetranychus urticaeKoch, Frankliniella occidentalis(Pergande), Ephestia kuehniella Zeller eggs and Artemia franciscana Kellogg cysts) and on three substrates (Multicel, sweet pepper leaf, and bean leaf) were determined in the laboratory. All experiments were carried out at 25 °C. On Multicel, mean developmental times on pollen ranged from 6.0 to 7.1 days, with the lowest value recorded on almond pollen and the highest on sweet pepper pollen. When reared on castor bean pollen significantly longer developmental times were obtained on a sweet pepper leaf compared to a bean leaf or Multicel. Developmental duration when offered T. urticaeon Multicel ranged between 6.1 and 6.9 days, on a bean leaf development was completed in 8.0 days. The longest developmental times on Multicel were recorded on Ephestia eggs (7.0 days) and on decapsulated Artemia cysts (7.5 days). No development beyond the protonymphal stage occurred in the absence of food or when encapsulated Artemia cysts or thrips larvae were offered on Multicel. On a sweet pepper leaf and a bean leaf, respectively 6.7 and 10.0% of the eggs reached adulthood when thrips larvae were provided as food; developmental times recorded here, were 9.0 and 8.3 days. Overall, immature mortality occurred mainly in the protonymphal stage and ranged from 0.0 to 36.7%. In conclusion, I. degenerans is able to feed on a variety of natural and unnatural foods, but thrips larvae and sweet pepper pollen are unfavourable food for immature development. This could compromise the establishment of this biological control agent when used against thrips in sweet pepper crops.     

Response of predatory mites with different rearing histories to volatiles of uninfested plants

The behavioural response of the predatory mite Phytoseiulus persimilis to volatiles from several host plants of its prey, spider mites in the genus Tetranychus, was investigated in a Y-tube olfactometer. A positive response to volatiles from tomato leaves and Lima bean leaves was recorded, whereas no response was observed to volatiles from cucumber leaves, or leaves of Solanum luteum and Solanum dulcamara.Different results were obtained for predators that differed in rearing history. Predators that were reared on spider mites (Tetranychus urticae) on Lima bean leaves did respond to volatiles from Lima bean leaves, while predators that had been reared on the same spider mite species but with cucumber as host plant did not respond to Lima bean leaf volatiles. This effect is compared with the effect of rearing history on the response of P. persimilis to volatile allelochemicals of prey-infested plant leaves.     

Life history and life table parameters of the predatory miceTyphlodromus talbii

The predatory miteTyphlodromus talbii Athias-Henriot occurs in European vineyards and is often associated with economically important species. Neither its role in vineyards nor the factors affecting its population dynamics and relationships with other phytoseiid species are well known. The development and the reproduction ofT. talbii were studied in the laboratory by rearing the predator on different kinds of food (Panonychus ulmi, Eotetranychus carpini, Colomerus vitis, Tydeus caudatus, Mesembryanthemum criniflorum pollen). Overwintered females reared on tydeids survived for long periods and laid eggs, but they died after a few days when spider mites or pollen were provided. Development occurred on all mite species but not on pollen. Developmental times on tydeids were shorter than on the other prey. Oviposition was recorded on tydeids and, to a lesser extent, on eriophyids but not on spider mites or pollen. Experiments on tydeids, which resulted as being the best food, were conducted at two temperatures (20° and 27°C). The highest temperature affected the duration of development and oviposition rates positively, but total fecundity was similar. Predators reared at 27°C consumed more prey than those reared at 20°C. The life table parameters of the species were evaluated onT. caudatus (at 20° and 27°C) and onC. vitis. The highest r_m ofT. talbii was found for individuals reared onT. caudatus at 27°C (0.165). Lower values were obtained on the same prey at 20°C (0.089) or onC. vitis (0.030). The feeding habits ofT. talbii may explain why the species coexists with the generalistAmblyseius aberrans orTyphlodromus pyri.     

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.     

Automatic mass-rearing of Amblyseius womersleyi (Acari: Phytoseiidae)

Using incorporated devices, Tetranychus urticae spider mites were rinsed from hydroponically-grown lima bean plants, collected, separated and blow-dried. This yielded a reliable and large volume of eggs and larvae, which were fed to Amblyseius womersleyi rearings on 15×5cm² polyethylene arenas. Of several feeding regimes tested, daily feeding of 10mg T. urticae eggs and larvae resulted in the highest predator population levels. The best harvest period was between 15 and 27 days, when predator density exceeded 600 mites per arena. A preliminary automatic mass-rearing device was tested for A. womersleyi. This incorporated both rearing and harvesting procedures. A micro-feeder was developed to supply the required volume of spider mites and maize pollen (1:1 mixture) to the predators. A Bakelite rearing arena reduced the space requirements of a polyethylene arena, was more durable and an essential component in the automatic mass-rearing and harvesting. Mite harvesting is carried out through the use of a vacuum-head harvester. Supplements of (sterilized) spider mites, pollen, vermiculite and wheat bran are automatically added to the predators. The devices for harvesting, filling and packing are incorporated and synchronized and the entire system is controlled by a single slide-switch. The design and system can be expanded without changing the basic processes and program, for example to adopt it for other species of predaceous mites.     

Euseiusfinlandicus (Acari: Phytoseiidae) as a potential biocontrol agent against Tetranychus urticae (Acari: Tetranychidae): life history and feeding habits on three different types of food

Life history and reproductive parameters of the generalist predatory mite Euseius (Amblyseius) finlandicus (Oudemans) were studied in the laboratory at 25 +/- 1 degrees C, with a 16L:8D photoperiod and 60 +/- 15% RH, to investigate its response to different food sources: an eriophyid mite Aceria sp., tulip pollen Tulipa gesnerana L., and two-spotted spider mite Tetranychus urticae Koch. Total developmental time of the immature stages was the shortest on eriophyid mites, followed by pollen, and then spider mites. Fecundity was highest on pollen (43.69 eggs; 1.63 eggs/female/day), then eriophyid mites (39.73 eggs; 1.37 eggs/female/day) and lowest on spider mites (18.16 eggs; 0.80 eggs/female/day). Intrinsic rate of increase (Rm), net reproductive rate (Ro) and finite rate of increase (lambda) followed the same pattern [pollen (0.168, 27.96 and 1.183, respectively), eriophyid mites (0.153, 20.81 and 1.167), spider mites (0.110, 9.44 and 1.119)]. Mean generation time (days) was the shortest on pollen (19.90), followed by eriophyid mites (20.02), and then spider mites (20.59). Average spider mite larvae consumed by E. finlandicus during immature stages were 9.18 for males and 11.85 for females. Adult E. finlandicus females consumed an average of 166.38 spider mite protonymphs during adult stage compared to an average of 66.55 by males. The number of prey protonymphs consumed per day by females was highest in the oviposition period, lower in the pre-oviposition period and the lowest in the post-oviposition period. The eriophyid mite as a prey recorded the shortest developmental time, while pollen as food recorded the highest oviposition rate in E. finlandicus. The potential of this predator as a biocontrol agent against T. urticae is discussed.     

Survival,development and reproduction of Euseius finlandicus (Oudemans) (Acari: Phytoseiidae) fed on various kinds of food substances

Laboratory experiments were conducted to investigate the effect of diet on the biology of the phytoseiid mite, Euseius finlandicus (Oudemans). The predatory mite was able to develop and reproduce better when fed on the eriophyid mites, Aceria olivi (Zaher and Abou-Awad), Aceria dioscoridis (Soliman and Abou-Awad) and Cisaberoptus kenyae (Keifer). The developmental time of immature stages was the shortest when fed on motile stages of eriophyid mite species, followed by the spider mite, Tetranychus urticae Koch, and then pollen grains of Ricinus communis L., Phoenix dactylifera L. and Helianthus annuus L. Total egg production was highest when the predator fed on A. olivi, A. dioscoridis and C. kenyae recording at the rate of 51.0 50.0 and 43.84 eggs/female, respectively, but lowest on pollen grains, R. communis, P. dactylifera and H. annuus at the rate of 11.96, 5.3 and 2.0 eggs/female, respectively. But, the reproduction was nil on the tetranychid mite, T. urticae. Also, sex ratio of the progeny favoured females, when the predatory mite was reared on the eriophyid preys. E. finlandicus recorded the highest intrinsic rate of increase (r_m?=?0.31 females/female/day) when fed on A. dioscoridis, followed by (0.30 and 0.23 females/female/day) when fed on A. olivi and C. kenyae, respectively. In contrast, the lowest intrinsic rate of increase (r_m?=??0.31) was noted when fed on H. annuus pollen grains. The eriophyid mite, as a prey, recorded the shortest developmental time and highest oviposition rate of E. finlandicus.     

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.     

Plantago asiatica groundcover supports Amblyseius tsugawai (Acari: Phytoseiidae) populations in apple orchards

Amblyseius tsugawai Ehara (Acari: Phytoseiidae) is a major predator of spider mites in orchards in Japan. To support populations in apple orchards in Akita Prefecture, northern Japan, we investigated whether it can use Plantago asiatica L. as a food resource. In laboratory tests, survival did not differ significantly between female adults given water only and those given a piece of P. asiatica leaf and water. However, A. tsugawai reproduces by feeding on P. asiatica pollen, and significantly more mites were reared on P. asiatica pollen than on tea pollen, which is commonly used for rearing phytoseiid mites. In orchards in 2013, female adults were observed on leaves of P. asiatica from late May; numbers peaked in mid-June and gradually decreased until late July. Most adults were found along veins on the hidden sides of the leaves. Female adults were also collected in Phyto traps attached to plants between late May and early August. Pollen production of P. asiatica peaked from mid-June to early July, when numbers of adults peaked on the plants. These results suggest that conservation of P. asiatica in apple orchards would sustain A. tsugawai populations.     

Influence of plant,animal and mixed resources on development of the zoophytophagous plant bug Campylomma verbasci (Hemiptera: Miridae)

The mullein bug, Campylomma verbasci (Meyer-Dür) (Hemiptera: Miridae), exploits both plant and animal resources. The aim of this study was (1) to evaluate the quality of different plant, animal and mixed diets (i.e. plant material or prey from the overwintering host, the summer host or the laboratory rearing) for the development and survival of mullein bug, and (2) to evaluate if the suitability of the resource changes according to the nymphal instar of C. verbasci. Mullein bug nymphs were reared individually in Petri dishes containing different diets and observed daily until reaching adulthood or dying. The rearing diet (living potato aphids?+?potato leaf?+?Ephestia eggs?+?apple pollen) was a high-quality diet. The medium-quality diets were apple fruit?+?apple pollen, Ephestia eggs and Sitotroga eggs. The low-quality diets included mullein leaf, frozen aphids, living aphids?+?potato leaf and apple fruit?+?living aphids?+?potato leaf. Finally, the inappropriate diets (when no nymphs reached adulthood) were agar gel, apple fruit, apple pollen, apple leaf, potato leaf, frozen spider mites and frozen conspecifics. When comparing the value of the diets for different instars, living aphids?+?potato leaf was a high-quality diet for third instar. Apple pollen and frozen conspecifics were low-quality diets for third instar. ‘Red Delicious’ fruit was a high-quality diet for fifth instar and low-quality for third instar. ‘Honeycrisp’ fruit constituted an inappropriate diet whatever the instar. Thus, a whole mixed diet maximises development and survival of C. verbasci nymphs.     

Pest species diversity enhances control of spider mites and whiteflies by a generalist phytoseiid predator

To test the hypothesis that pest species diversity enhances biological pest control with generalist predators, we studied the dynamics of three major pest species on greenhouse cucumber: Western flower thrips, Frankliniella occidentalis (Pergande), greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and two-spotted spider mites, Tetranychus urticae Koch in combination with the predator species Amblyseius swirskii Athias-Henriot. When spider mites infested plants prior to predator release, predatory mites were not capable of controlling spider mite populations in the absence of other pest species. A laboratory experiment showed that predators were hindered by the webbing of spider mites. In a greenhouse experiment, spider mite leaf damage was lower in the presence of thrips and predators than in the presence of whiteflies and predators, but damage was lowest in the presence of thrips, whiteflies and predators. Whitefly control was also improved in the presence of thrips. The lower levels of spider mite leaf damage probably resulted from (1) a strong numerical response of the predator (up to 50 times higher densities) when a second and third pest species were present in addition to spider mites, and (2) from A. swirskii attacking mobile spider mite stages outside or near the edges of the spider mite webbing. Interactions of spider mites with thrips and whiteflies might also result in suppression of spider mites. However, when predators were released prior to spider mite infestations in the absence of other pest species, but with pollen as food for the predators, we found increased suppression of spider mites with increased numbers of predators released, confirming the role of predators in spider mite control. Thus, our study provides evidence that diversity of pest species can enhance biological control through increased predator densities.     

Effect of diet on the photoperiodic induction of diapause in three species of predatory mite,Amblyseius potentillae,A. cucumeris andTyphlodromus pyri

The predatory mitesAmblyseius potentillae, A. cucumeris andTyphlodromus pyri entered diapause in response to a short-day photoperiodic regime, when they were reared on pollen of the ice plant,Dorotheanthus bellidiformis. With pollen of the broad bean,Vicia faba, as food, however, diapause was virtually absent inA. potentillae andA. cucumeris under the same short-day regime, but full diapause was found inT. pyri. The importance of carotenoids for the photoperiodic response in these predatory mites is discussed.     

Assessing the Effects of Bt Maize on the Predatory Mite Neoseiulus cucumeris

The investigation of Neoseiulus cucumeris in the context of the ecological risk assessment of insect resistant transgenic plants is of particular interest as this omnivorous predatory mite species is commercially available and considered important for biological control. In a multitrophic feeding experiment we assessed the impact of Bt maize on the performance of N. cucumeris when offered spider mites (Tetranychus urticae) reared on Bt (Bt11, Syngenta) or non-Bt maize (near isogenic line) and Bt or non-Bt maize pollen as a food source. Various parameters including mortality, development time, oviposition rate were measured. Spider mites were used as a prey for N. cucumeris, since these herbivores are known to contain similar levels of Cry1Ab toxin, when reared on Bt maize, as those found in the transgenic leaf material. In contrast, toxin levels in pollen of this transgenic cultivar are very low. No differences in any of the parameters were found when N. cucumeris was fed with spider mites reared on Bt and non-Bt maize. Pollen was shown to be a less suitable food source for this predator as compared to spider mites. Moreover, subtle effects on female N. cucumeris (9% longer development time and 17% reduced fecundity) were measured when fed with pollen originating from Bt maize as compared to non-Bt maize pollen. Our findings indicate that the predatory mite N. cucumeris is not sensitive to the Cry1Ab toxin as no effects could be detected when offered Bt-containing spider mites, and that the effects found when fed with Bt maize pollen can be assigned to differences in nutritional quality of Bt and non-Bt maize pollen. The significance of these findings is discussed with regard to the ecological relevance for risk assessment of transgenic plants.     

Non-prey food for subsistence of Amblyseius idaeus (Acari: Phytoseiidae) on cassava in Africa

The nutritional effects of pollen from cassava, oil palm, castor bean, Leucaena leucocephala and a phloem exudate from cassava were tested in the laboratory for their effect on survivorship and oviposition of Amblyseius idaeus (Denmark & Muma). Survival and longevity of even-aged females were enhanced on the aforementioned non-prey diets when compared with the control of no food. Castor bean pollen provided sufficient nutrition to induce an irregular and low ovipositional rate of A. idaeus over a five week interval. Oviposition ceased after 48 h in the presence of the other non-prey foods or free-water only. These studies suggest that A. idaeus is capable of switching or supplementing its diet with non-prey foods during periods when spider mite populations are low.     

Active optical sensor assessment of spider mite damage on greenhouse beans and cotton

The two-spotted spider mite, Tetranychus urticae Koch, is an important pest of cotton in mid-southern USA and causes yield reduction and deprivation in fiber fitness. Cotton and pinto beans grown in the greenhouse were infested with spider mites at the three-leaf and trifoliate stages, respectively. Spider mite damage on cotton and bean canopies expressed as normalized difference vegetation index indicative of changes in plant health was measured for 27 consecutive days. Plant health decreased incrementally for cotton until day 21 when complete destruction occurred. Thereafter, regrowth reversed decline in plant health. On spider mite treated beans, plant vigor plateaued until day 11 when plant health declined incrementally. Results indicate that pinto beans were better suited as a host plant than cotton for rearing T. urticae in the laboratory.     

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.     

Genetic improvement of Amblyseius finlandicus (Acari: Phytoseiidae): laboratory selection for resistance to azinphosmethyl and dimethoate

Amblyseius finlandicus (Oudemans) was selected in the laboratory for resistance to azinphosmethyl and dimethoate by subjecting adult females to increasing concentrations of dried residues of dimethoate and azinphosmethyl on detached bean leaves. The first eight selections were done with dimethoate. Slide-dip bioassays indicated selection with dimethoate increased dimethoate resistance 1.8-fold and azinphosmethyl resistance 2.6-fold. These resistances appeared to be quite stable: a 1.2 to 1.3-fold decrease in resistance ratios was observed in a subculture after 10 months without selections. No decrease was observed after 9 months without selections in a pooled colony that consisted of both resistant and susceptible mites. The dimethoate-selected colony was subsequently selected eight times with azinphosmethyl. About 15 % of the mites survived the last selection round with 2,500 ppm, which is 2.5 times the highest recommended field rate in Finnish apple orchards. At the end of the selection program, based on slide-dip bioassays, the total increase in resistance to dimethoate was about two-fold and to azinphosmethyl about 5.4-fold compared to the unselected base colony from which the selected colony was derived. The LC₅₀ value for azinphosmethyl was 14 times higher in the selected colony (451.3 ppm a.i.) compared to the most susceptible colony tested. A similar level of resistance to both pesticides was achieved after six azinphosmethyl selections on a mixed colony that was initiated by pooling mites from five field-collected colonies and the dimethoate-selected lines. Year-to-year variation in azinphosmethyl LC₅₀ values of the unselected base colony was high, with values varying from 83.8 to 348.7 ppm a.i., demonstrating the need to test a reference strain in each bioassay. Results of the azinphosmethyl selections and the subsequent slide-dip bioassays suggest that the resistant strain could tolerate field rates of azinphosmethyl (300–950 ppm a.i.) used in Finnish apple orchards.     

Biological control of Pacific mites and Willamette mites in San Joaquin Valley vineyards: part III. Role of tydeid mites

In the absence of spider mites, tydeids (Pronematus anconaiBaker and Pronematus ubiquitus [Mc Gregor ]) may serve as alternate prey to maintain good numbers of the predatory mite, Metaseiulus occidentalis (Nesbitt ) (Acarina, Phytoseiidae), late in the season. This late-season predator and alternate prey relationship is necessary to stabilize Pacific mite populations and perpetuate balance in San Joaquin Valley vineyards. Thriving laboratory colonies of tydeids were reared on a diet of windblown pollens, including cattail pollen (Typha sp., Typhaceae) and bottlebrush pollen (Melaleuca sp., Myrtaceae).M. occidentalis was successfully reared on a diet of tydeids and ovipositing predator females were obtained. In addition, pollen dusted on grapevines significantly increased both tydeid and indirectly M. occidentalis populations late in the season. These studies suggest that artificially disseminating cattail pollen or manipulating good pollen producing flora in and around vineyards may be used to correct situations where Pacific mites have become serious pests.