Beyond polyphagy and opportunism: natural prey of hunting spiders in the canopy of apple trees

Spiders (Araneae) form abundant and diverse assemblages in agroecosystems such as fruit orchards, and thus might have an important role as natural enemies of orchard pests. Although spiders are polyphagous and opportunistic predators in general, limited information exists on their natural prey at both species and community levels. Thus, the aim of this study was to assess the natural prey (realized trophic niche) of arboreal hunting spiders, their role in trophic webs and their biological control potential with direct observation of predation events in apple orchards. Hunting spiders with prey in their chelicerae were collected in the canopy of apple trees in organic apple orchards in Hungary during the growing seasons between 2013 and 2019 and both spiders and their prey were identified and measured. Among others, the composition of the actual (captured by spiders) and the potential (available in the canopy) prey was compared, trophic niche and food web metrics were calculated, and some morphological, dimensional data of the spider-prey pairs were analyzed. Species-specific differences in prey composition or pest control ability were also discussed. By analyzing a total of 878 prey items captured by spiders, we concluded that arboreal hunting spiders forage selectively and consume a large number of apple pests; however, spiders’ beneficial effects are greatly reduced by their high levels of intraguild predation and by a propensity to switch from pests to alternative prey. In this study, arboreal hunting spiders showed negative selectivity for pests, no selectivity for natural enemies and positive selectivity for neutral species. In the trophic web, the dominant hunting spider taxa/groups (Carrhotus xanthogramma, Philodromus cespitum, Clubiona spp., Ebrechtella tricuspidata, Xysticus spp. and ‘Other salticids’) exhibit different levels of predation on different prey groups and the trophic web’s structure changes depending on the time of year. Hunting spiders show a high functional redundancy in their predation, but contrary to their polyphagous nature, the examined spider taxa showed differences in their natural diet, exhibited a certain degree of prey specialization and selected prey by size and taxonomic identity. Guilds (such as stalkers, ambushers and foliage runners) did not consistently predict either prey composition or predation selectivity of arboreal hunting spider species. From the economic standpoint, Ph. cespitum and Clubiona spp. were found to be the most effective natural enemies of apple pests, especially of aphids. Finally, the trophic niche width of C. xanthogramma and Ph. cespitum increased during ontogeny, resulting in a shift in their predation. These results demonstrate how specific generalist predators can differ from each other in aspects of their predation ecology even within a relatively narrow taxonomic group.

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The Influence of Spray Programs on the Fauna of Apple Orchards in Nova Scotia. VII. Effects on Some Beneficial Arthropods

The Canadian Entomologist ◽

10.4039/ent86128-3 ◽

1954 ◽

Vol 86 (3) ◽

pp. 128-135 ◽

Cited By ~ 23

Author(s):

A. W. MacPhee ◽

K. H. Sanford

Keyword(s):

Nova Scotia ◽

Natural Enemies ◽

Apple Orchards ◽

Beneficial Arthropods ◽

Population Densities ◽

Apple Trees ◽

Arthropod Pests

The toxicities of a large number of spray chemicals to arthropod pests are well known. In most instances, observations on the effects of such materials on natural enemies have beeen incidental to other studies, and little has been published on experiments designed to determine the direct toxicities of the chemicals to beneficial species. The effects of spray chemicals on the predators and parasites of the major pests of apple trees in Nova Scotia have been investigated as part of a broader project on the factors that influence population densities of orchard arthropods, as outlined by Pickett et al. (31).

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The Influence of Spray Programs on the Fauna of Apple Orchards in Nova Scotia. XIII. Effects of Perthane on Predators

The Canadian Entomologist ◽

10.4039/ent94928-9 ◽

1962 ◽

Vol 94 (9) ◽

pp. 928-934 ◽

Cited By ~ 12

Author(s):

K. H. Sanford ◽

F. T. Lord

Keyword(s):

Nova Scotia ◽

Natural Enemies ◽

Apple Orchards ◽

Natural Control ◽

Predator Prey ◽

Phytophagous Mites ◽

Ecological Principles ◽

Apple Pests

In Nova Scotia, a spray program that integrates chemical and natural control of apple pests has been evolved which is both economical and satisfactory. Among the natural enemies of injurious arthropods that have been favoured by this program are a number of general predators. Further investigation of the ecological principles on which integration is based requires a more intensive knowledge of the factors that influence the densities of these predators. Because of the difficulties of investigating these factors in the orchard, methods of simplifying the predator-prey systems have been sought (Lord, 1956, 1962). These attempts assessed the effects of low dosages of DDT on the interrelationships of phytophagous mites and their natural enemies.

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Seasonal wound presence and susceptibility to Neonectria ditissima infection in New Zealand apple trees

New Zealand Plant Protection ◽

10.30843/nzpp.2015.68.5799 ◽

2015 ◽

Vol 68 ◽

pp. 250-256 ◽

Cited By ~ 3

Author(s):

N.T. Amponsah ◽

M. Walter R.M. Beresford ◽

R.W.A. Scheper

Keyword(s):

New Zealand ◽

Artificial Inoculation ◽

Early Winter ◽

Leaf Fall ◽

Apple Orchards ◽

Apple Trees ◽

Leaf Scar ◽

Fruit Thinning ◽

Different Types

Leaf scar wounds are important sites for Neonectria ditissima infection of apple trees Monitoring leaf fall in Scilate/Envy and Braeburn trees to estimate leaf scar wound presence showed maximum leaf scar incidence occurred in June (early winter) Wounds detected in New Zealand apple orchards were bud scale scars fruit thinning and picking wounds leaf scars and pruning cuts Picking wounds are caused during harvest where the pedicel is detached from the shoot Susceptibility of these different types of wounds was determined using artificial inoculation of N ditissima conidia during the season Pruning cut wounds were the most susceptible followed by fruit picking and thinning wounds and the least susceptible were leaf scar wounds No infections were observed when bud scale wounds were inoculated There was no difference in wound susceptibility between cultivars but overall Scilate/Envy wounds developed more lesions than Braeburn wounds

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A Comparison of Flower and Grass Strips for Augmentation of Beneficial Arthropods in Apple Orchards

Frontiers in Sustainable Food Systems ◽

10.3389/fsufs.2021.697864 ◽

2021 ◽

Vol 5 ◽

Author(s):

Zhaoke Dong ◽

Mengjing Xia ◽

Cheng Li ◽

Baofeng Mu ◽

Zhiyong Zhang

Keyword(s):

Natural Enemies ◽

Cover Crops ◽

Habitat Management ◽

Management Practices ◽

Management Practice ◽

The Other ◽

Alternative Prey ◽

Apple Orchards ◽

Beneficial Arthropods ◽

Arthropod Predators

Sowing plants that provide food resources in orchards is a potential habitat management practice for enhancing biological control. Flowering plants (providing pollen and nectar) and grasses (providing alternative prey) can benefit natural enemies in orchards; however, little is known about their relative importance. We studied the effect of management practices (flower strips, grass strips, and spontaneous grass) on arthropod predators under organic apple management regimes in apple orchards in Beijing, China. Orchards located at two different sites were assessed for 3 years (2017–2019). The cover crops had a significant impact on the abundance and diversity of arthropod predators. The grass treatment consistently supported significantly greater densities of alternative prey resources for predators, and predators were more abundant in the grass than in the other treatments. The Shannon–Wiener diversity was significantly higher for the cover crop treatment than for the control. Community structure was somewhat similar between the grass and control, but it differed between the flower treatment and grass/control. Weak evidence for an increase in mobile predators (ladybirds and lacewings) in the orchard canopy was found. Ladybirds and lacewings were more abundant in the grass treatment than in the other treatments in 2019 only, while the aphid abundance in the grass treatment was lowest. The fact that grass strips promoted higher predator abundance and stronger aphid suppression in comparison to the flower strips suggests that providing alternative prey for predators has great biocontrol service potential. The selection of cover crops and necessary management for conserving natural enemies in orchards are discussed in this paper.

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Gradient Boosting Estimation of the Leaf Area Index of Apple Orchards in UAV Remote Sensing

Remote Sensing ◽

10.3390/rs13163263 ◽

2021 ◽

Vol 13 (16) ◽

pp. 3263

Author(s):

Zhijie Liu ◽

Pengju Guo ◽

Heng Liu ◽

Pan Fan ◽

Pengzong Zeng ◽

...

Keyword(s):

Remote Sensing ◽

Leaf Area Index ◽

Leaf Area ◽

Shaanxi Province ◽

Gradient Boosting ◽

Support Vector ◽

Apple Orchards ◽

Apple Trees ◽

Area Index ◽

Spatial Efficiency

The leaf area index (LAI) is a key parameter for describing the canopy structure of apple trees. This index is also employed in evaluating the amount of pesticide sprayed per unit volume of apple trees. Hence, numerous manual and automatic methods have been explored for LAI estimation. In this work, the leaf area indices for different types of apple trees are obtained in terms of multispectral remote-sensing data collected with an unmanned aerial vehicle (UAV), along with simultaneous measurements of apple orchards. The proposed approach was tested on apple trees of the “Fuji”, “Golden Delicious”, and “Ruixue” types, which were planted in the Apple Experimental Station of the Northwest Agriculture and Forestry University in Baishui County, Shaanxi Province, China. Five vegetation indices of strong correlation with the apple leaf area index were selected and used to train models of support vector regression (SVR) and gradient-boosting decision trees (GBDT) for predicting the leaf area index of apple trees. The best model was selected based on the metrics of the coefficient of determination (R2) and the root-mean-square error (RMSE). The experimental results showed that the gradient-boosting decision tree model achieved the best performance with an R2 of 0.846, an RMSE of 0.356, and a spatial efficiency (SPAEF) of 0.57. This demonstrates the feasibility of our approach for fast and accurate remote-sensing-based estimation of the leaf area index of apple trees.

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Conserving carnivorous arthropods: an example from early-season cranberry (Ericaceae) flooding

The Canadian Entomologist ◽

10.4039/tce.2017.66 ◽

2018 ◽

Vol 150 (2) ◽

pp. 265-273

Author(s):

J. van Zoeren ◽

C. Guédot ◽

S.A. Steffan

Keyword(s):

Biological Control ◽

Pest Management ◽

Natural Enemies ◽

Control Strategies ◽

Cultural Control ◽

Generalist Predators ◽

Early Season ◽

Insecticide Application ◽

Insecticide Spray

AbstractBiological control plays an important role in many integrated pest management programmes, but can be disrupted by other control strategies, including chemical and cultural controls. In commercial cranberry (Vaccinium macrocarpon Aiton; Ericaceae) production, a spring flood can replace an insecticide application, providing an opportunity to study the compatibility of the flood (a cultural control) with biological control. We suspect that chemical controls will tend to reduce the number of natural enemies, while the flood, through removal of detritus and detritivores, may cause generalist predators to prey-switch to consume proportionally more pest individuals. We measured the abundance of herbivores (Lepidoptera), detritivores, Arachnida, and parasitoids (Hymenoptera) every week for six weeks in Wisconsin (United States of America) cranberry beds following either an insecticide spray or a cultural control flood. We found that detritivore populations rapidly declined in both flood and spray treatments; conversely, carnivore populations (spiders and parasitoids) were more abundant in the flooded beds than in sprayed beds. Populations of key cranberry pests were similar between flooded and sprayed beds. Our results showed that early-season flooding preserved more natural enemies than an insecticide application. This increase in natural enemy abundance after the flood may allow for greater continuity in herbivore suppression, potentially providing a basis for long-term cranberry pest management.

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Ontogenetic shifts in natural diet, chelae, and mandible of an omnivorous freshwater crab (Aegla uruguayana): linking morphology and function

Canadian Journal of Zoology ◽

10.1139/cjz-2020-0290 ◽

2021 ◽

Author(s):

Maria Florencia Viozzi ◽

Juan Manuel Cabrera ◽

Federico Giri ◽

Debora de Azevedo Carvalho ◽

Verónica Williner

Keyword(s):

Morphological Changes ◽

Feeding Strategy ◽

Stomach Contents ◽

Trophic Niche ◽

Composition Analysis ◽

Diet Change ◽

Geometric Morphometric ◽

Natural Diet ◽

Plant Remains ◽

And Function

We analyze whether ontogenetic diet change in Aegla uruguayana (Schmitt, 1942) is related to the morphological changes in chelae and mandibles. We use a combination of scanning electron microscope observation (SEM), dietary composition analysis (stomach observation, trophic niche amplitude, trophic overlap, and feeding strategy), and geometric morphometric tools (discriminant analysis and two-block partial least squares analysis). The two structures analyzed by SEM show differences between juvenile and adult specimens, both in their cuticle and morphology specializations. In juveniles, the absence of the lobular tooth is the notable feature. However, in adult sizes it is marked development. Both groups have simple setae with infracuticular articulation and denticles with different arrangements between groups. In the incisive mandible process, the teeth and spines present sharper points in juveniles and considerable wear in adults. Aegla uruguayana presented two trophic strategies: a profile of more predatory traits when younger and mostly detritivorous when adults. The analysis of geometric morphometry substantiates the patterns observed in SEM and stomach contents analysis. The morphology of smaller specimens is associated with the consumption of animal items (ephemeropterans larvae and cladocerans), while in those of larger sizes; it is related to the consumption of plant remains.

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Cover crops in Victorian apple orchards: Effects on production, natural enemies and pests across a season

Crop Protection ◽

10.1016/j.cropro.2009.03.021 ◽

2009 ◽

Vol 28 (8) ◽

pp. 675-683 ◽

Cited By ~ 36

Author(s):

Nicole J. Bone ◽

Linda J. Thomson ◽

Peter M. Ridland ◽

Peter Cole ◽

Ary A. Hoffmann

Keyword(s):

Natural Enemies ◽

Cover Crops ◽

Apple Orchards

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Can Generalist Predators Control Bemisia tabaci?

Insects ◽

10.3390/insects11110823 ◽

2020 ◽

Vol 11 (11) ◽

pp. 823

Author(s):

Arash Kheirodin ◽

Alvin M. Simmons ◽

Jesusa C. Legaspi ◽

Erin E. Grabarczyk ◽

Michael D. Toews ◽

...

Keyword(s):

Bemisia Tabaci ◽

Natural Enemies ◽

Cropping Systems ◽

Review Literature ◽

Generalist Predators ◽

Generalist Predator ◽

Predator Species ◽

Molecular Gut Content Analysis ◽

Biocontrol Potential ◽

Substantial Control

The whitefly, Bemisia tabaci, has developed resistance to many insecticides, renewing interest in the biological control of this global pest. Generalist predators might contribute to whitefly suppression if they commonly occur in infested fields and generally complement rather than interfere with specialized natural enemies. Here, we review literature from the last 20 years, across US cropping systems, which considers the impacts of generalist predators on B. tabaci. Laboratory feeding trials and molecular gut content analysis suggest that at least 30 different generalist predator species willingly and/or regularly feed on these whiteflies. Nine of these predators appear to be particularly impactful, and a higher abundance of a few of these predator species has been shown to correlate with greater B. tabaci predation in the field. Predator species often occupy complementary feeding niches, which would be expected to strengthen biocontrol, although intraguild predation is also common and might be disruptive. Overall, our review suggests that a bio-diverse community of generalist predators commonly attacks B. tabaci, with the potential to exert substantial control in the field. The key challenge will be to develop reduced-spray plans so that generalist predators, and other more specialized natural enemies, are abundant enough that their biocontrol potential is realized.

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