Hyperpredation by generalist predatory mites disrupts biological control of aphids by the aphidophagous gall midge Aphidoletes aphidimyza

Biological control of different species of pest with various species of generalist predators can potentially disrupt the control of pests through predator-predator interactions. We evaluate the impact of three species of generalist predatory mites on the biological control of green peach aphids, Myzus persicae (Sulzer) with the aphidophagous gall midge Aphidoletes aphidimyza (Rondani). The predatory mites tested were Neoseiulus cucumeris (Oudemans), Iphiseius degenerans (Berlese) and Amblyseius swirskii Athias–Henriot, which are all commonly used for pest control in greenhouse sweet pepper. All three species of predatory mites were found to feed on eggs of A. aphidimyza, even in the presence of abundant sweet pepper pollen, an alternative food source for the predatory mites. In a greenhouse experiment on sweet pepper, all three predators significantly reduced population densities of A. aphidimyza, but aphid densities only increased significantly in the presence of A. swirskii when compared to the treatment with A. aphidimyza only. This stronger effect of A. swirskii can be explained by the higher population densities that this predator reached on sweet pepper plants compared to the other two predator species. An additional experiment showed that female predatory midges do not avoid oviposition sites with the predator A. swirskii. On the contrary, they even deposited more eggs on plants with predatory mites than on plants without. Hence, this study shows that disruption of aphid control by predatory mites is a realistic scenario in sweet pepper, and needs to be considered when optimizing biological control strategies.     

The role of native vegetation on infection rates of Calacarus heveae (Acari: Eriophyidae) by Hirsutella thompsonii (Ascomycota: Ophiocordycipitaceae)

Hirsutella thompsonii (Fischer) (Ascomycota: Ophiocordycipitaceae), a fungal pathogen, often causes high mortality in populations of Calacarus heveae Feres (Acari: Eriophyidae), an important pest mite in rubber tree plantations (Hevea brasiliensis Muell. Arg., Euphorbiaceae). However, the ecological and climatic factors regulating this host-pathogen system are poorly known. We compared fungal infections in agroforestry and traditional rubber plantations to evaluate the role of native vegetation and climatic factors on infection rates of C. heveae by H. thompsonii. While the prevalence of H. thompsonii was higher in managed rubber tree plantations, the abundance of C. heveae was about three times higher in traditional plantations. Abundance of C. heveae, agroecosystem management type and microclimatic variables were responsible for driving the infection rates of H. thompsonii. Native vegetation was a source for H. thompsonii and also modified the crop’s microclimate, which contributed to its maintenance in the crop fields. Therefore, appropriate management practices may enhance the effects of entomopathogens on conservative biological control of pest mites in agroforestry systems.     

Studies on Anhydrobiosis of Pratylenchus thornei

Large populations of Pratylenchus thornei, a winter pest of cereals, legumes, and potatoes in the northern Negev region of Israel, survive 7-8 months of summer drought and return to full activity at the beginning of the rainy season. To demonstrate that it survives the summer in an anhydrobiotic state, all developmental stages of P. thornei were exposed to gradually reduced relative humidity (RH) using glycerin water solutions. At 97.7% RH the nematodes were coiled and able to survive exposure to 0% RH. About 40% of artificially desiccated nematodes could be reactivated by gradually increasing the humidity to the final water environment. Desiccated nematodes could withstand temperatures up to 40 C. Reactivated individuals showed intestines apparently devoid of reserve materials. Only 3% survived three cycles of desiccation and reactivation. P. thornei reactivated after anhydrobiosis multiplied twice as much within Vicia sativa roots as did fresh nematodes.     

Influence of cerrado fragments in the distribution of mites in rubber tree crop

The aim of this study was to verify whether fragments of cerrado influence the composition of the mite fauna on rubber trees. Five transects distant 50 m, being the first in the edge near the native areas and the last 200 m inside the crop, were established in each rubber tree crop in southern State of Mato Grosso. In each transect five plants were chosen, and seven leaves were collected from each plant. During one year, 25 quantitative samplings were conducted in two rubber tree crops. The lowest number of phytophagous mites occurred in the transect closer to the native vegetation, and the highest number, in the most distant from the native vegetation. The largest diversity was also observed in the transect closer to the neighboring vegetation. Ten species of predatory mites were also registered in neighboring native areas. These data suggest the movement of predatory mites from the native areas to the monoculture. These natural areas can possibly supply alternative food and habitat for natural enemies of phytophagous mites in the period of food scarceness in the rubber tree crop. The presence of native areas close to culture areas should be taken into account in the elaboration of programs of ecological management of pests.     

Population Fluctuation and Damage Caused by Phytophagous Mites on Three Rubber Tree Clones

Our aim was to investigate the population fluctuation and the damage caused by the phytophagous mites Calacarus heveae Feres, Tenuipalpus heveae Baker, and Eutetranychus banksi (McGregor) on clones FX 2784, FX 3864, and MDF 180 in rubber tree crops from southeastern Bahia, Brazil. Moreover, we tested for the influence of climatic variables on occurrence patterns of these species throughout weekly samples performed from October to April. The infestation peaks was between mid-January and late February. The clones FX 2784 and FX 3864 had the highest infestations and more severe damage possibly caused by C. heveae, which was the most frequent and abundant species in all clones. We found that sunlight duration and rainfall were the most important factors for C. heveae while T. heveae was affected by rainfall and temperature. Eutetranychus banksi was only affected by sunlight duration. However, the best models had low goodness of fit. We concluded that the clones FX 2784 and FX 3864 had a higher susceptibility to mite attack, and the association between climatic variables and favorable physiological conditions were determinant for the population increase of the species from January to April.     

Sequential Sampling Plan for Tenuipalpus heveae Baker (Acari: Tenuipalpidae) on Rubber Tree

The objective of the present study was to develop a sequential sampling plan for the decision-making process to control Tenuipalpus heveae Baker (Acari: Tenuipalpidae), an important pest of the rubber tree crop. The experimental area was represented by 1,000 plants of the RRIM 600 clone divided in 100 plots with 10 plants each. Leaves were collected and the number of mites determined under laboratory conditions. The sequential sampling plan was developed in accordance with the Sequential Test Likelihood Ratio. The value 0.10 was pre-established for α and β representing type I and type II errors, respectively. The level of control adopted was six mites per 12 cm². The operating characteristic curve and the curve of maximum expected sample were determined. Two lines were generated: the upper one, when the condition for chemical control is recommended (S1?=?23.3080?+?2.1972); and the lower, when chemical control is not recommended (S0?=??23.3080?+?2.1972). Sample size for the decision-making process to control T. heveae requires 6 to 18 plants.     

Environment and host-plant genotype effects on the seasonal dynamics of a predatory mite on cassava in sub-humid tropical Africa

1 In tropical dry seasons, survival of small arthropods such as predatory mites is often negatively affected by low relative humidity (RH). For species that do not diapause or migrate to refuges, the ability of the habitat to mitigate climatic conditions becomes crucial.
2 The relative effect of macro-habitat (dry grassland hill, humid multiple cropping area, humid riparian forest) and microhabitat (host-plant genotypes with hairy, semi-hairy and glabrous apices) on the seasonal dynamics of the phytoseiid mite Typhlodromalus aripo , a predator of Mononychellus tanajoa on cassava, was examined in a field experiment during a dry season. The effect of RH and plant genotype on T. aripo egg survival was determined in an environment control chamber.
3 Predator abundance was higher in humid multiple cropping areas and on hairy cassava compared with the other habitat types and cassava genotypes.
4 Discriminant and regression analyses showed that the predator's dry season persistence was related to high RH, high plant vigour and hairy apices, but not to prey abundance.
5 In the controlled climate experiment, the effect of host-plant morphology was evident only at the intermediate RH level of 55%. An effect of apex hairiness was not found.
6 It is concluded that the effect of genotype on T. aripo persistence diminishes under low RH conditions, and that supportive effects of apex hairs become effective only in the field, probably through protection from wind and/or intraguild predation. Humid multiple cropping areas planted with hairy and vigorous cassava genotypes are suitable dry season reservoirs for T. aripo .     

Domatia morphology and mite occupancy of Psychotria horizontalis (Rubiaceae) across the Isthmus of Panama

Leaf domatia are small plant structures in vein axials on the undersides of leaves that are often inhabited by mites of several species. The mites are presumed to benefit the plant because they are predatory or fungivorous. The domatia are thought to provide the mites shelter from predators and changes in relative humidity, and in exchange, the mites protect the plant from small herbivores and fungal spores. Differences in relative humidity can affect food availability, changing the interaction between plants and mites. We examined domatium morphology of the shrub Psychotria horizontalis (Rubiaceae) and its associated mite diversity at three sites along the rainfall gradient of the Isthmus of Panama, during the dry and wet seasons. The dry forest had a domatium morphology consistent with providing greater desiccation protection, with trichomes and a smaller domatium opening relative to domatium size (size/opening ratio). Additionally, this size/opening ratio was significantly higher in the dry season than in the wet season at all three sites. Mite diversity was highest at the intermediate rainfall site with a large degree of overlap with the other sites, whereas the dry site and wet site shared few mite species. More fungivorous mites were present in the moist forests and more facultative feeders on fungal spores and small mites in the dry forest. The average mite size at each site matched the average domatium size at each site. The dry forest had small mites in small domatia, whereas the moist forests had larger mites in larger domatia. While these data are primarily observational, the site and seasonal differences in domatium morphology and mite diversity are consistent with two main hypotheses: (1) that protection from changes in humidity would be particularly important when humidity was low, such as in the dry forest and during the dry season (2) more fungivorous mites would be found in domatia of the moist forests. The data presented here further highlight the close adaptive relationship between leaf domatia on plants and the mites that inhabit them.     

Chimpanzee predation in the Mahale mountains from August 1979 to May 1982

Fifty-four episodes of predatory behavior of wild chimpanzees were recorded in Mahale, western Tanzania, from August 1979 to May 1982. The chimpanzees most frequently hunt in two seasons, during May, and from August to December. Longer-term fecal analysis indicates that predation frequency is significantly higher in the dry than in the rainy season. The seasonality of predation might be the result of the sum of various ecological factors, at least one of which is the birth season of the prey species. Most of the prey are juvenile blue duiker, bushbuck, bushpig, red colobus, and red-tailed monkeys. Sex difference is recognized in the prey selection and in the hunting method employed. Apparent local difference in the predatory behavior between Mahale and Combe chimpanzees (in Mahale,females hunt more frequently, and blue duiker is the most frequent prey) can be understood in terms of the difference either in the observation methods or in the faunal diversity and density. Other aspects of predatory behavior also are reported.     

Contrasting engineering effects of leaf‐rolling caterpillars on a tropical mite community

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湿度对木薯单爪螨Mononchellus mcgregori发育与繁殖的影响

【目的】木薯单爪螨是新入侵我国的重要检疫性害螨,主要危害木薯,也可危害橡胶。近年来,该螨种群数量迅速增多,扩散范围不断增大,目前已在海南、云南、广西、广东等重要木薯产区发生并加重危害,危害严重时可导致木薯减产40%~60%。湿度是影响木薯单爪螨发育和繁殖的重要因素之一,但有关该方面的研究较少。【方法】通过室内饲养,观察比较了不同湿度条件下木薯单爪螨发育及繁殖情况。【结果】当湿度为75%和85%时,卵孵化率均达100%,平均每雌产卵量分别达49.22和43.67粒,雌成螨寿命分别为21.00和22.00 d;当湿度为55%和95%时,卵孵化率和后代产卵量显著降低,雌成螨寿命显著缩短;当湿度为65%时,卵孵化率、平均每雌产卵量以及成螨寿命均与75%和85%湿度处理无显著差异,但其发育历期显著延长。【结论】75%和85%是木薯单爪螨发育与繁殖的适宜湿度条件。     

Comparison of the mass and energy exchange of a pasture and a mature transitional tropical forest of the southern Amazon Basin during a seasonal transition

This research utilized tower‐based eddy covariance to quantify the trends in net ecosystem mass (CO₂ and H₂O vapor) and energy exchange of important land‐cover types of NW Mato Grosso during the March–December 2002 seasonal transition. Measurements were made in a mature transitional (ecotonal) tropical forest near Sinop, Mato Grosso, and a cattle pasture near Cotriguaçú, Mato Grosso, located 500 km WNW of Sinop. Pasture net ecosystem CO₂ exchange (NEE) was considerably more variable than the forest NEE over the seasonal transition, and the pasture had significantly higher rates of maximum gross primary production in every season except the dry–wet season transition (September–October). The pasture also had significantly higher rates of whole‐ecosystem dark respiration than the forest during the wetter times of the year. Average (±95% CI) rates of total daily NEE during the March–December 2002 measurement period were 26±15 mmol m^?2 day^?1 for the forest (positive values indicate net CO₂ loss by the ecosystem) and ?38±26 mmol m^?2 day^?1 for the pasture. While both ecosystems partitioned more net radiation (R_n) into latent heat flux (L_e), the forest had significantly higher rates of L_e and lower rates of sensible heat flux (H) than the pasture; a trend that became more extreme during the onset of the dry season. Large differences in pasture and forest mass and energy exchange occurred even though seasonal variations in micrometeorology (air temperature, humidity, and radiation) were relatively similar for both ecosystems. While the short measurement period and lack of spatial replication limit the ability to generalize these results to pasture and forest regions of the Amazon Basin, these results suggest important differences in the magnitude and seasonal variation of NEE and energy partitioning for pasture and transitional tropical forest.     

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).     

Leaf domatia do not affect population dynamics of the predatory mite Iphiseiodes zuluagai

Leaves of plants of several families possess small cavities or tufts of hair where leaf veins bifurcate. These so-called acarodomatia are usually inhabited by predatory and fungivorous mites, which utilize domatia as shelter against adverse conditions or against other predators and cannibals. Plants may benefit from the presence of the mites through reduced densities of herbivores or plant-pathogenic fungi. It has therefore been suggested that domatia mediate a mutualistic interaction between plants and mites. We tested the hypothesis that cavity-like domatia on coffee plants benefit the predatory mite Iphiseiodes zuluagai through providing protection against adverse weather conditions and other predators in three field experiments. We manipulated plant domatia by blocking all on one group of plants, whereas a second group of plants with open natural domatia served as a control. Predatory mite populations were provided with pollen as a food source during part of two experiments. Experiments were done in the dry and rainy season to test the effects of adverse weather conditions and with or without an insect glue barrier on the plant to prevent access of ground-dwelling hyperpredators. High temperatures had a significant negative effect on predator densities in all experiments, whereas rainfall and humidity affected densities in one and two experiments respectively. None of the experiments showed a significant effect of domatia manipulation on mite numbers, or a significant interaction between weather parameters and domatia, suggesting that domatia did not protect against these adverse weather conditions. Nevertheless, predatory mites were frequently observed inside the domatia, suggesting that the mites benefit from using domatia. Perhaps domatia offer protection against hyperpredators, which were rarely observed during our experiments.     

Effectiveness of the BT mite trap for detecting the storage mite pests, Acarus siro, Lepidoglyphus destructor and Tyrophagus longior

Traps have been used extensively to provide early warning of hidden pest infestations. To date, however, there is only one type of trap on the market in the U.K. for storage mites, namely the BT mite trap, or monitor. Laboratory studies have shown that under the test conditions (20 °C, 65% RH) the BT trap is effective at detecting mites for at least 10 days for all three species tested: Lepidoglyphus destructor, Tyrophagus longior and Acarus siro. Further tests showed that all three species reached a trap at a distance of approximately 80 cm in a 24 h period. In experiments using 100 mites of each species, and regardless of either temperature (15 or 20 °C) or relative humidity (65 or 80% RH), the most abundant species in the traps was T. longior, followed by A. siro then L. destructor. Trap catches were highest at 20 °C and 65% RH. Temperature had a greater effect on mite numbers than humidity. Tests using different densities of each mite species showed that the number of L. destructor found in/on the trap was significantly reduced when either of the other two species was dominant. It would appear that there is an interaction between L. destructor and the other two mite species which affects relative numbers found within the trap.The British Crowns right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.This revised version was published online in May 2005 with a corrected cover date.     

Comparison of the predation capacities of two soil-dwelling predatory mites,Gaeolaelaps aculeifer and Stratiolaelaps scimitus (Acari: Laelapidae), on three thrips species

Soil-dwelling predatory mites are natural enemies of various soil pest insects and mites. Both Gaeolaelaps aculeifer (Canestrini) and Stratiolaelaps scimitus (Womersley) are commercialized natural enemies of thrips, but there is little information on the predation rate of these predatory mites on different thrips species. We compared their predation capacities on three thrips species, Frankliniella occidentalis, F. intonsa, and Thrips palmi, which are major pests of various horticultural plants. The predatory rate of G. aculeifer was higher than that of S. scimitus. Both predator species fed on more T. palmi thrips than F. occidentalis or F. intonsa thrips, which may be attributable to the smaller body size of T. palmi than the other thrips. Predation rates of female adults were 2.6–2.8 times higher than those of deutonymphs in both species. Predation rates were not separated according to the various developmental stages (i.e., second instar larva, pupa, or adult) of thrips; however, deutonymphs fed on fewer adults than larvae or pupae of F. occidentalis. Our results suggest that both G. aculeifer and S. scimitus are active predators that can prey during any of their developmental stages and on any species of thrips tested.     

Relative contribution of biotic and abiotic factors to the population density of the cassava green mite, Mononychellus tanajoa (Acari: Tetranychidae)

The cassava green mite, Mononychellus tanajoa, is a key pest of cassava, Manihot esculenta Crantz (Euphorbiaceae), and it may be kept in check by naturally occurring predatory mites of the family Phytoseiidae. In addition to predatory mites, abiotic factors may also contribute to regulate pest mite populations in the field. Here, we evaluated the population densities of both M. tanajoa and the generalist predatory mite Euseius ho DeLeon (Acari: Phytoseiidae) over the cultivation cycle (11 months) of cassava in four study sites located around the city of Miranda do Norte, Maranhão, Brazil. The abiotic variables rainfall, temperature and relative humidity were also recorded throughout the cultivation cycle of cassava. We determined the relative importance of biotic (density of E. ho) and abiotic (rainfall, temperature and relative humidity) factors to the density of M. tanajoa. The density of M. tanajoa increased whereas the density of E. ho remained constant throughout time. A hierarchical partitioning analysis revealed that most of the variance for the density of M. tanajoa was explained by rainfall and relative humidity followed by E. ho density and temperature. We conclude that abiotic factors, especially rainfall, were the main mechanisms driving M. tanajoa densities.     

The effect of forest fragments on abundance,diversity and species composition of predatory ants in sugarcane fields

Habitat loss and fragmentation have gradually caused loss of diversity and consequently the decline of ecological services. This study aimed to evaluate the effect of tropical forest fragments as natural habitats (river valley fragments and plateau fragments) on the community of predatory and omnivorous ants in nearby sugarcane fields. Twenty fields adjacent to these fragments were selected and evaluated one (dry season) and four months (rainy season) after harvest. In each field, ants were sampled in five linear plots (10 m inside the fragment, 0 m (field path between field and fragment), 5 m, 50 m and 100 m inside the crop fields). Each plot comprised ten sardine baits in a row parallel to the field edge. Species richness and frequency of ant species decreased with increasing distance from the forest fragments. Inside fields, species richness and frequency were higher during the period of vegetative growth (rainy season) than after harvest (dry season). Ant communities of sugarcane fields and forest fragments were more similar later in the season than directly after sugarcane harvest suggesting recolonization of the fields from the fragments. Several ant species were limited to forest fragments after harvest but occurred later in the season also in sugarcane fields confirming the potential contribution of fragments to the recolonization process and therefore to biological control of sugarcane-dominated pest insects.     

Driving factors of the communities of phytophagous and predatory mites in a physic nut plantation and spontaneous plants associated

Seasonal changes in climate and plant diversity are known to affect the population dynamics of both pests and natural enemies within agroecosystems. In Brazil, spontaneous plants are usually tolerated in small-scale physic nut plantations over the year, which in turn may mediate interactions between pests and natural enemies within this agroecosystem. Here, we aimed to access the influence of seasonal variation of abiotic (temperature, relative humidity and rainfall) and biotic (diversity of spontaneous plants, overall richness and density of mites) factors on the communities of phytophagous and predatory mites found in a physic nut plantation and its associated spontaneous plants. Mite sampling was monthly conducted in dicotyledonous and monocotyledonous leaves of spontaneous plants as well as in physic nut shrubs over an entire year. In the dry season there was a higher abundance of phytophagous mites (Tenuipalpidae, Tarsonemidae and Tetranychidae) on spontaneous plants than on physic nut shrubs, while predatory mites (Phytoseiidae) showed the opposite pattern. The overall density of mites on spontaneous plants increased with relative humidity and diversity of spontaneous plants. Rainfall was the variable that most influenced the density of mites inhabiting physic nut shrubs. Agroecosystems comprising spontaneous plants associated with crops harbour a rich mite community including species of different trophic levels which potentially benefit natural pest control due to increased diversity and abundance of natural enemies.     

Effects of Temperature and Relative Humidity on Development,Reproduction, and Predation in Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae)

The predatory gall midge Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) is a biological control agent for twospotted spider mites on greenhouse vegetable crops. Effects of temperature and relative humidity (RH) on development of immatures, reproduction, and prey capture were determined in order to confirm the suitability of F. acarisuga for use in greenhouses. Developmental time ranged from 10 days at 27°C to 34 days at 15°C. At 20°C, developmental time was significantly shorter at 96% RH than at 84% RH. There was very poor survival of immatures at 64% RH and none at 36%. Lifespan of adult females decreased with increasing temperature, but temperature had no significant effect on number of eggs laid. At 20°C, lifespan was longer at 84 and 96% RH than at 64 or 36% RH. The number of spider mites attacked by 3-day-old larvae over 8 h increased with increasing temperature from 15 to 27°C. The number of mites attacked also increased with increasing RH at 27°C. We conclude that F. acarisuga will complete its life cycle and reproduce under conditions typically found in vegetable greenhouses in northern temperate climates. However, extended periods of low RH (<60% RH) could reduce reproduction and survivorship sufficiently to impair the predator's action against spider mite populations.