Non-pest prey do not disrupt aphid predation by a web-building spider

2015 ◽  
Vol 106 (1) ◽  
pp. 91-98 ◽  
Author(s):  
K.D. Welch ◽  
T.D. Whitney ◽  
J.D. Harwood
Keyword(s):  
Natural Enemies ◽  
Nutritional Quality ◽  
Generalist Predators ◽  
Generalist Predator ◽  
Diversification Strategy ◽  
Molecular Gut Content Analysis ◽  
Foraging Tactics ◽  
Pest Suppression ◽  
The Cost ◽  
Web Building

AbstractA generalist predator's ability to contribute to biological control is influenced by the decisions it makes during foraging. Predators often use flexible foraging tactics, which allows them to pursue specific types of prey at the cost of reducing the likelihood of capturing other types of prey. When a pest insect has low nutritional quality or palatability for a predator, the predator is likely to reject that prey in favour of pursuing alternative, non-pest prey. This is often thought to limit the effectiveness of generalist predators in consuming aphids, which are of low nutritional quality for many generalist predators. Here, we report behavioural assays that test the hypothesis that the generalist predator, Grammonota inornata (Araneae: Linyphiidae), preferentially forages for a non-pest prey with high nutritional quality (springtails), and rejects a pest prey with low nutritional quality (aphids). In no-choice assays, molecular gut-content analysis revealed that spiders continued to feed on the low-quality aphids at high rates, even when high-quality springtails were readily available. When provided a choice between aphids and springtails in two-way choice tests, spiders did not show the expected preference for springtails. Decision-making by spiders during foraging therefore appears to be sub-optimal, possibly because of attraction to the less frequently encountered of two preys as part of a dietary diversification strategy. These results indicate that behavioural preferences alone do not necessarily compromise the pest-suppression capacity of natural enemies: even nutritionally sub-optimal pest prey can potentially be subject to predation and suppression by natural enemies.

scholarly journals Can Generalist Predators Control Bemisia tabaci?

Insects ◽  
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.

Cursorial spiders retard initial aphid population growth at low densities in winter wheat

2008 ◽  
Vol 98 (3) ◽  
pp. 249-255 ◽  
Author(s):  
K. Birkhofer ◽  
E. Gavish-Regev ◽  
K. Endlweber ◽  
Y.D. Lubin ◽  
K. von Berg ◽  
...  
Keyword(s):  
Population Growth ◽  
Functional Groups ◽  
Arable Land ◽  
Aphid Population ◽  
Generalist Predators ◽  
Generalist Predator ◽  
Molecular Technique ◽  
Predator Species ◽  
Web Building ◽  
The Impact

AbstractGeneralist predators contribute to pest suppression in agroecosystems. Spider communities, which form a substantial fraction of the generalist predator fauna in arable land, are characterized by two functional groups: web-building and cursorial (non-web-building) species. We investigated the relative impact of these two functional groups on a common pest (Sitobion avenae, Aphididae) in wheat by combining a molecular technique that revealed species-specific aphid consumption rates with a factorial field experiment that analyzed the impact, separately and together, of equal densities of these two spider functional groups on aphid population growth. Only cursorial spiders retarded aphid population growth in our cage experiment, but this effect was limited to the initial aphid-population growth period and low-to-intermediate aphid densities. The molecular analysis, which used aphid-specific primers to detect aphid DNA in predator species, detected the highest proportion of aphid-consuming individuals in two cursorial spiders: the foliage-dwelling Xysticus cristatus (Thomisidae) and the ground-active Pardosa palustris (Lycosidae). The results suggest that manipulating the community composition in favour of pest-consuming functional groups may be more important for improving biological control than fostering predator biodiversity per se. Agricultural management practices that specifically foster effective species or functional groups (e.g. mulching for cursorial spiders) should receive more attention in low-pesticide farming systems.

Differences in shell strength of native and non-native oysters do not extend to size classes that are susceptible to a generalist predator

2012 ◽  
Vol 63 (12) ◽  
pp. 1201 ◽  
Author(s):  
Emma M. Wilkie ◽  
Melanie J. Bishop
Keyword(s):  
Native Species ◽  
Shell Height ◽  
Trophic Relationships ◽  
Generalist Predators ◽  
Generalist Predator ◽  
Eastern Australia ◽  
Saccostrea Glomerata ◽  
The Cost ◽  
Native Oyster ◽  
Predator Defence

Whether non-native species proliferate to pest status can depend on top-down control from native predators. Among epifaunal molluscs, the shell serves as a main line of anti-predator defence and shell strength may determine the ease with which generalist predators can penetrate prey. We assessed whether, in eastern Australia, the faster growth of the non-native Pacific oyster, Crassostrea gigas, than that of the native Saccostrea glomerata comes at the cost of reduced investment in shell thickening, rendering the non-native oyster more susceptible to a generalist predator, the muricid gastropod Morula marginalba. Laboratory tests confirmed that among larger (>50-mm shell height) oysters, the shells of C. gigas were weaker than those of similar-sized S. glomerata. There were, however, no differences in shell strength or thickness between smaller S. glomerata and C. gigas of the size consumed by M. marginalba. In the absence of shell-strength differences among smaller oysters, M. marginalba preferentially consumed native over non-native oysters. When, however, M. marginalba had no choice of prey item, C. gigas was consumed at the same rate as the native oyster. Our results add to growing evidence that the invasion of C. gigas in eastern Australian estuaries is, at present, causing minimal disruption to trophic relationships.

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

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.

scholarly journals Eastern Coyotes (Canis latrans var.) consuming large ungulates in a multi-ungulate system

2020 ◽  
Vol 134 (1) ◽  
pp. 45-51
Author(s):  
Juliana Balluffi-Fry ◽  
Liane B. Nowell ◽  
Murray M. Humphries
Keyword(s):  
Prey Species ◽  
Canis Latrans ◽  
Feeding Habits ◽  
Castor Canadensis ◽  
Generalist Predators ◽  
Generalist Predator ◽  
Wide Range ◽  
Game Reserve ◽  
Varied Diet ◽  
American Beaver

The feeding habits of generalist predators often vary among populations and regions. For example, Coyote (Canis latrans), which is a generalist predator distributed across North America, occupies a wide range of habitats and has a highly varied diet. In this observational study, we quantified the presence of mammalian prey items in 50 Eastern Coyote (Canis latrans var.) scats collected in late spring and summer in a private game reserve in southwestern Quebec. Nearly all scats contained hair of White-tailed Deer (Odocoileus virginianus; 44%), Moose (Alces americanus; 38%), or American Beaver (Castor canadensis; 38%). Although all three species are known to be consumed by coyotes, such a high proportion of Moose and White-tailed Deer simultaneously occurring in the diet of coyotes has not been previously reported. The uniqueness of the study area, with its relatively high abundance of all three prey species, may account for the uniqueness of the diet of Eastern Coyotes living there.

Site fidelity and the costs of movement among territories: an example from colonial web-building spiders

2001 ◽  
Vol 79 (11) ◽  
pp. 2094-2100 ◽  
Author(s):  
Elizabeth M Jakob ◽  
Adam H Porter ◽  
George W Uetz
Keyword(s):  
Direct Observation ◽  
Site Fidelity ◽  
Prey Capture ◽  
Adaptive Significance ◽  
Central Core ◽  
Heterogeneous Habitats ◽  
Alternative Behaviors ◽  
Potential Benefits ◽  
The Cost ◽  
Web Building

Species differ in whether they exhibit strong site fidelity or move readily among sites. To understand the adaptive significance of site fidelity it is necessary to measure the cost of relocating to new sites, but this is very difficult with most species because it entails following individuals during the entire course of their transition. We studied the colonial web-building spider Metepeira incrassata (Araneae: Araneidae), which defends individual orb webs within a large, shared frame web. Colonies are heterogeneous habitats, with more prey but also more predators at the periphery of the colony relative to the central core. We measured relocation costs in this species by breaking them into the following components, (i) searching costs, (ii) establishment costs, and (iii) lost-opportunities costs, or the potential benefits of alternative behaviors that an animal might engage in if it were not relocating. We observed spiders that were in the process of establishing their orb webs at the start of the foraging day and conducted experiments to examine the costs of relocation by transferring spiders between locations within the colony. Transferred spiders had more fights with conspecifics than non-transferred spiders did, and the number of fights was positively correlated with the distance moved. However, searching and establishment costs seem unimportant, as individuals moving within their territories were as active as individuals moving to new sites. Transferred spiders faced greater lost-opportunities costs in the form of time spent on prey-capture orbs, as they significantly delayed orb construction. Lost-opportunities costs seem to be the most important component of relocation costs in this species and are likely to be generally important among species. This study is one of the few to document movement costs through direct observation.

Prey-specific foraging tactics in a web-building spider

2013 ◽  
Vol 15 (4) ◽  
pp. 375-381 ◽  
Author(s):  
Kelton D. Welch ◽  
Kenneth F. Haynes ◽  
James D. Harwood
Keyword(s):  
Foraging Tactics ◽  
Web Building

Food habits of European badgers (Meles meles) along an altitudinal gradient of Mediterranean environments: a field test of the earthworm specialization hypothesis

2004 ◽  
Vol 82 (1) ◽  
pp. 41-51 ◽  
Author(s):  
Emilio Virgós ◽  
Julián G Mangas ◽  
José Antonio Blanco-Aguiar ◽  
Germán Garrote ◽  
Nuria Almagro ◽  
...  
Keyword(s):  
Environmental Gradient ◽  
Elevation Gradient ◽  
Meles Meles ◽  
Generalist Predators ◽  
Habitat Conditions ◽  
Mediterranean Studies ◽  
Mediterranean Environments ◽  
Wide Range ◽  
Foraging Tactics ◽  
European Badgers

Food specialization by European badgers (Meles meles) is a largely debated controversy. Data from Mediterranean areas indicate small importance of earthworms (Lumbricus spp.) in badger diet and support the idea that badgers are generalist predators. Nevertheless, only dry areas have been sampled so far. We studied badger diet in six areas along an elevation gradient with different rainfall and habitat conditions, which influenced earthworm availability. We evaluated the influence of earthworm availability on badger diet along this environmental gradient. Badgers used a wide range of prey items in the different habitats and seasons sampled. In contrast with other Mediterranean studies, earthworms made an important contribution to badger diet (27% of estimated volume). Earthworm occurrence in the diet was high in elevated and wet habitats and in spring and autumn–winter. Earthworm consumption was nonlinearly related to availability, indicating high intake compared with availability in wet areas. Moreover, in summer, availability was virtually zero in all habitats, whereas consumption averaged 15% volume of the diet. We tentatively suggest that badgers compensate for variations in earthworm availability by changing their foraging tactics. This suggests that badgers could be viewed as specialist foragers for earthworms in some Mediterranean environments.

scholarly journals Generalist predators disrupt parasitoid aphid control by direct and coincidental intraguild predation

2011 ◽  
Vol 102 (2) ◽  
pp. 239-247 ◽  
Author(s):  
M. Traugott ◽  
J.R. Bell ◽  
L. Raso ◽  
D. Sint ◽  
W.O.C. Symondson
Keyword(s):  
Trophic Interactions ◽  
Intraguild Predation ◽  
Generalist Predators ◽  
Generalist Predator ◽  
Cereal Aphid ◽  
Aphid Parasitoid ◽  
Trophic Links ◽  
Aphid Control ◽  
Effective Conservation ◽  
Predator Community

AbstractGeneralist predators and parasitoids are considered to be important regulators of aphids. The former not only feed on these pests, but might also consume parasitoids at all stages of development. This direct or coincidental interference affects the natural control of aphids, the scale of which is largely unknown, and it has rarely been examined under natural conditions. Here, molecular diagnostics were used to track trophic interactions in an aphid-parasitoid-generalist predator community during the build-up of a cereal aphid population. We found that generalist predators, principally carabid and staphylinid beetles as well as linyphiid spiders, had strong trophic links to both parasitoids and aphids. Remarkably, more than 50% of the parasitoid DNA detected in predators stems from direct predation on adult parasitoids. The data also suggest that coincidental intraguild predation is common too. Generalist predators, hence, disrupt parasitoid aphid control, although the levels at which the predators feed on pests and parasitoids seem to vary significantly between predator taxa. Our results suggest that taxon-specific trophic interactions between natural enemies need to be considered to obtain a more complete understanding of the route to effective conservation biological control.

Sign in / Sign up

Export Citation Format

Share Document