Predatory behaviors of Neoseiulus californicus and Galendromus helveolus (Acari: Phytoseiidae) attacking Oligonychus perseae (Acari: Tetranychidae)

Predatory behaviors of Neoseiulus californicus (McGregor) and Galendromus helveolus (Chant) attacking Oligonychus perseae Tuttle, Baker and Abbatiello on avocado leaves were videotaped and analyzed. Behaviors were recorded for “fresh” predators that were used ≤ 48 hr post receipt from a commercial insectary and “cold stored” predators that were maintained at 12°C for ≈ 14 days. Fresh and cold stored G. helveolus were observed to attack O. perseae only after invading webbed nests. Conversely, fresh and cold stored N. californicus employed three different modes of predatory attack: (1) intercepting and attacking migrant O. perseae outside of web nests; (2) attacking prey through nest webbing; or (3) invading and attacking O. perseae inside nests. Predatory efficacy of both N. californicus and G. helveolus was reduced following cold storage, as both species engaged in certain predatory behaviors less frequently in comparison to predators that were not stored at low temperatures. Our observed results for N. californicus and G. helveolus attacking O. perseae are interpreted in relation to the chaetotaxy hypothesis, which proposes that phytoseiid invasion efficiency and propensity of webbed nests is facilitated by dorsal setal lengths. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectroscopic and enzymatic evidence for membrane-bound electron transport carriers and hydrogenase and their relation to cytochrome b function in Methanosarcina barkeri

Abstract Membranes prepared from Methanosarcina barkeri cultured on acetate were examined for electron carriers using electron paramagnetic resonance (EPR) and optical spectroscopy. EPR analysis of membrane suspensions demonstrated multiple iron-sulfur centers of the 4Fe-4S type, a hihg-spin heme-like species and possibly rebredoxin. Optical spectroscopy demonstrated that a b -type cytochrome was reduced by molecular hydrogen and oxidized by methyl coenzyme M. A membrane-bound hydrogenase activity (14 μM · min⁻¹ (mg protein)⁻¹) was detected. This suggests a putative role for cytochrome b and hydrogenase in electron transfer and methyl-group reduction during aceticlastic methanogenesis.     

Etudes comparatives de l'influence de la température et de la nourriture sur le développement deAmblyseius andersoni,Neoseiulus fallacis,Galendromus longipilus etTyphlodromus pyri [Acari: Phytoseiidae]

Résumé L'étude en laboratoire de la biologie du développement deAmblyseius andersoni, Neoseiulus fallacis, Galendromus longipilus etTyphlodromus pyri a permis de calculer les seuils de développement et le taux intrinsèque d'accroissement naturel à 20°C lorsque ces espèces sont nourries avecTetranychus urticae. Le taux de fécondité spécifique à l'age des 4 espèces a été déterminé en utilisant comme proie soitT. urticae, soitPanonychus ulmi. PourA. andersoni et pourT. pyri, P. ulmi constitue une nourriture meilleure queT. urticae, contrairement àN. fallacis etG. longipilus, dont le taux d'accroissement est supérieur quand ils se nourrissent deT. urticae. PourG. longipilus, P. ulmi constitue même une nourriture nettement suboptimale. Pour les femelles de toutes les espèces on a pu mettre en évidence la faculté d'adapter le taux de fécondité et la durée d'oviposition au nombre des proies disponibles. En termes de fécondité, cela permet à ces espèces de réaliser presque tout leur potentiel, indépendamment de la ration quotidienne de nourriture.      

Evaluation of methods to control Phytonemus pallidus and Anthonomus rubi in organic strawberry production

Abstract:  Use of the predatory mite Neoseiulus cucumeris (Oudemans) (Acari, Phytoseiidae) and a fleece cover in combination with pyrethrum application showed potential for control of two important pests in organic production of strawberry ( Fragaria  ×  ananassa Duch.), although there were some unexpected interactions between pyrethrum and the release of N. cucumeris that need to be investigated further. Two cultivars, Honeoye and Cavendish, were treated with pyrethrum with or without fleece to control strawberry blossom weevils [ Anthonomus rubi Herbst. (Col., Curculionidae)] and N. cucumeris was released to control strawberry mites [ Phytonemus pallidus (Banks) (Acari, Tarsonemidae)]. Number of strawberry mites, number of flower buds damaged by the weevil, incidence of grey mould and powdery mildew, and fruit yield were measured in two consecutive fruiting seasons. In Honeoye, the fleece in combination with pyrethrum decreased the proportion of damaged buds by 11–23% and increased yield by 49–91 g per plant. When pyrethrum was used alone it did not influence the number of damaged buds or yield. This indicates that the combined treatment was more effective because of the fleece. In Cavendish, the fleece and pyrethrum treatments were not found to be effective. Almost no P. pallidus was found in Honeoye and the results were not analysable. In plots with Cavendish where N. cucumeris had been released, there were approximately 50% fewer P. pallidus from the end of August onwards in 2003. However, this response did not significantly influence the succeeding year's yield. The number of fruits infected with fungi was very low and no effects were observed for any of the treatments.     

Interactions among phytophagous mites, and introduced and naturally occurring predatory mites, on strawberry in the UK

In choice test experiments on strawberry leaf disc arenas the phytoseiid mites Neoseiulus californicus and N. cucumeris were more effective than Typhlodromus pyri as predators of the phytophagous mites Tetranychus urticae and Phytonemus pallidus. There were no preferences shown for either prey by any of these predators. In multiple predator leaf disc experiments both Phytoseiulus persimilis and N. cucumeris significantly reduced numbers of T. urticae eggs and active stages; this effect was seen when the two species were present alone or in combination with other predator species. Neoseiulus californicus was less effective at reducing T. urticae numbers, and T. pyri was not effective; no interaction between predator species was detected in these experiments. When T. urticae alone was present as prey on potted plants, P. persimilis and N. californicus were the only phytoseiids to significantly reduce T. urticae numbers. These two predator species provided effective control of T. urticae when P. pallidus was also present; however, none of the predators reduced numbers of P. pallidus. There were no significant negative interactions when different species of predators were present together on these potted plants. In field experiments, releases of both P. persimilis and N. cucumeris significantly reduced T. urticae numbers. However, there was a significant interaction between these predator species, leading to poorer control of T. urticae when both species were released together. These results show the importance of conducting predator/prey feeding tests at different spatial scales.     

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.     

Factors affecting the distribution of a predatory mite on greenhouse sweet pepper

The predatory mite Neoseiulus cucumeris is used for biological control of phytophagous mites and thrips on greenhouse cucumber and sweet pepper. In a previous study, N. cucumeris provided effective control of broad mite but was only rarely found on the sampled leaves, raising questions about the factors affecting N. cucumeris distribution. To determine the distribution of N. cucumeris, leaves of pepper plants were sampled three times per day: just after sunrise, at noon and just before sunset for two years and throughout a 24 h period in one year. The presence of other mites and insects was recorded. Biotic (pollen) and abiotic (temperature, humidity) factors were monitored from the three plant levels. The effect of direct and indirect sunlight on the mites was assessed. N. cucumeris was found primarily in flowers; however, the mite’s distribution was affected by other predators (intraguild predation); in the presence of the predatory bug Orius laevigatus virtually no mites occurred in the flowers. Whereas temperature and humidity varied from the top to the lower level of the plants, apparently neither these factors nor the presence of pollen outside the flowers influenced mite distribution. N. cucumeris was found to be negatively phototropic; therefore N. cucumeris were pre-conditioned to light by rearing under light conditions for 4 months before being released. The light-reared mites were initially more numerous during the noon sampling period, however, rearing conditions caused only a temporary and non-significant change in distribution.     

巴氏新小绥螨毒死蜱抗性选育及生物学特性

[目的]明确巴氏新小绥螨Neoseiulus barkeri毒死蜱抗性对其生物学特性的影响,为抗药性捕食螨田间应用提供理论基础.[方法]在室内采用药膜法测定毒死蜱对巴氏新小绥螨的毒力,以半致死浓度(lethal medium concentration,LC50)为选择压力,对巴氏新小绥螨敏感种群进行逐代汰选.应用生命...     

Hops as a metapopulation landscape for tetranychid-phytoseiid interactions: perspectives of intra- and interplant dispersal

Population densities, distributions and dispersal of Neoseiulus fallacis (Garman) and Tetranychus urticae (Koch) on individual hop plants, Humulus lupulus L. were studied for attributes of metapopulations such as empty patches, asynchrony of subpopulations, extinction of subpopulations, and dispersal of predators and prey among patches. Occupancy of hop leaves by predators or prey was stable over a season with 69–75% of leaves having neither predators nor prey, 4–15% with prey mites only, 9–17% with both predators and prey mites and 6–10% with predaceous mites only. Stability of occupancy classes through time indicated that inherently unstable predator and prey subpopulations developed asynchronously. Flagged hop leaves showed the existence of many empty individual leaves, colonization of some by prey, then by predators, then extinction of both, and then recolonization by spider mites. This illustrated the existence of empty patches, extinction of subpopulations, and dispersal of predators and prey to empty patches. This differed from spider mites and phytoseiid predators on apple foliage where there was a progression of occupancy status, indicating synchronous development of subpopulations on individual plants. Studies of predator and prey dispersal between hop plants showed that removal of basal leaves to 1.5 m high, a common agronomic practice, greatly limited dispersal of the predaceous mites but not the spider mites. Retaining basal leaves facilitated interplant movement of predators and improved the extent and timing of biological control. Through management, N. fallacis dispersal may be adjusted so that the entire hop planting becomes a metapopulation landscape, leading to greater stability and persistence of predator–prey within a season.     

Larval size relative to larval feeding, cannibalism of larvae, egg or adult female size and larval–adult setal patterns among 13 phytoseiid mite species

Phytoseiid mite larvae vary in size and feeding type. We compared larval size to feeding by larvae, cannibalism of larvae by adult females, egg and adult female size and the setae lengths of larvae and adults among 13 species. There was no relationship between size of larvae and either feeding by larvae or cannibalism of larvae by adult female mites. Correlations were highest between larval size as measured by idiosoma plus extended leg lengths and adult female size of idiosoma plus extended leg lengths (r²=0.746), while next highest was larval idiosoma length and adult female idiosoma length (r²=0.662) and then larval idiosoma length and egg length (r²=0.579). Based on idiosoma length, Phytoseiulus persimilis had the largest larvae (non-feeding) among species and Euseius finlandicus had the smallest larvae (obligatory feeding). However, based on idiosoma length plus extended leg length, obligatory feeding larvae (on pollen or mites) of E. finlandicus and Euseius hibisci were largest and facultative feeding larvae (on mites) of Neoseiulus californicus and obligatory feeding larvae (on mites) of Galendromus occidentalis were the smallest. Among species with non- or facultative feeding larvae, Amblyseius andersoni and Neoseiulus barkeri had larger larvae and Typhlodromus pyri and Neoseiulus fallacis had smaller larvae when leg lengths were included in larval size. Setae lengths of larvae versus adult females (after adjustment for body sizes) showed high correlation for j6 (r²=0.942) and s4 (r²=0.854), but low correlation for larval Z4 versus adult female Z4 (r²=0.084) or Z5 (r²=0.063). Overall, larval morphological traits were most closely correlated to traits of other life stages, although for setae there were some exceptions. Differences in the functions of setae j6, s4 and Z4 in the larva versus adult female are discussed.