Effect of boundary type and season on predatory arthropods associated with field margins on New Zealand farmland

Pitfall traps were used to monitor predatory arthropod numbers along two types of field boundary, a post and wire fence line and a Cupressus macrocarpa hedge, along the same paddock margin in Canterbury, New Zealand, over 24 months. The seven most abundant predator groups recorded were: Araneae > Phalangiidae > Staphylinidae > Coccinellidae > Chilopoda > Hemerobiidae > Carabidae. Araneae, Phalangiidae, Staphylinidae, Chilopoda and Hemerobiidae were found in larger numbers at the wire fence than at the hedge site, whereas the numbers of Carabidae and Coccinellidae adults exhibited no field margin preference. However, more species of Araneae and Staphylinidae were caught at the hedge site, whereas species richness of carabid beetles was greatest at the wire fence. Principal component analysis clearly separated the samples collected from the two habitats based on the assemblages of Araneae, Staphylinidae and Carabidae, and certain species in each of these taxonomic groups appeared to be particularly associated with one boundary type or the other. All the main taxonomic groups exhibited clear seasonal patterns, with distinct peaks in abundance occurring at certain times of the year. The results of the study reinforce the idea that management of field boundaries can be used to manipulate the type and abundance of particular groups of predatory arthropods, and that seasonal patterns should be taken into account in schemes of integrated pest management so that any adverse effects of biocide application on these beneficial species may be minimised.     

The effect of cover plants management on soil invertebrate fauna in vineyard in Northern Italy

Cover crops are largely used in vineyard management to improve ecological services such as pest and weed control, soil protection from erosion and soil water balance. Few data are available about the effects of cover crops on soil fauna and, in particular, on important generalist predators such as Carabidae and Araneae. We compare the effects of five different cover crops treatments: Sweet Alyssum, Phacelia, Buckwheat, Faba bean and a mixture of Vetch and Oat. A three years experimental trial was developed in Northern Italy. Soil fauna was investigated using pitfall traps. Cover crops seriously affected soil fauna of most taxa. Higher abundance of predators, in particular Carabidae and Staphylinidae, was present in treatments with legumes (Faba bean and Vetch and Oat) while soil Araneae seemed not to be affected. No vineyard pests seemed to be positively affected by cover crops. We confirm the importance of cover crops in increasing soil predator abundance and consequently improving pest control.     

Effects of mowing frequency on densities of natural enemies in three Pacific Northwest pear orchards

Effects of mowing frequency on ground cover composition and on numbers of predators, parasitoids, and select phytophagous arthropods in the ground cover of three reduced‐insecticide pear orchards were determined. Concurrent samples taken in the tree canopy (with beating trays) and in the herbicide strips on the orchard floor (with pitfall traps) tested whether counts of natural enemies in these two habitats were also affected by mowing regime. A reduction in frequency of mowing from two to three times per month (= control) to once per month or once per growing season led to increased cover of grasses, broadleaf plants, and broadleaf plants in flower. Sweep net samples of natural enemies in the ground cover were dominated numerically by spiders (Araneae), parasitic Hymenoptera, and predatory Heteroptera, with lesser numbers of other taxa (Syrphidae, Neuroptera, Coccinellidae). Predators and parasitoids showed substantial increases in numbers associated with decreased mowing frequency. Sweep net counts of aphids, Lygus spp. (Heteroptera: Miridae), and leafhoppers/planthoppers, all potential prey of predators, also increased significantly with decreased mowing frequency. In the pitfall samples, only the European earwig (Forficula auricularia L.) (Dermaptera: Forficulidae) exhibited a change in counts associated with mowing treatment; numbers of earwigs in pitfall traps declined as mowing frequency decreased. For the beat tray samples, mean tray counts for most natural enemy taxa were higher in the less frequently mowed plots, but significantly (P < 0.05) so only for two taxa: spiders and a predatory mirid, Deraeocoris brevis (Uhler) (Heteroptera: Miridae). It remains to be determined whether biological control of pests in the tree canopy can be enhanced by manipulating mowing frequency. Questions raised by this study include whether there is extensive movement by natural enemies between the ground cover and tree canopy, and whether plot size affects the likelihood of showing that mowing frequency influences predator densities in the tree canopy.     

Sampling epigeal arthropods: an evaluation of fenced pitfall traps using mark-release-recapture and comparisons to unfenced pitfall traps in arable crops

The efficiency of fenced pitfall traps for estimating the density of commonly occurring epigeal predatory beetles was examined using mark-release-recapture. Most beetles of those recovered were recaptured within one week of their release. For seven of the ten species tested recapture rates were over 70%, with higher rates for the larger species. The predatory arthropod species composition captured using fenced pitfall traps was compared to unfenced pitfall traps in winter wheat, spring barley and winter oilseed rape. Compositional analysis revealed that the dominance structure of seven carabid beetle (Coleoptera: Carabidae) taxa differed between the trap types and month of sampling in winter wheat and spring barley, but differences were small with the exception of a few taxa. Linear relationships between the two techniques were found for some carabid and rove beetles (Coleoptera: Staphylinidae). The dominance structure of seven linyphiid spider (Araneae: Linyphiidae) taxa differed between the two trap types in wheat but not barley, although large differences were restricted to two taxa. No linear relationships between the two techniques were found for any of the Linyphiidae examined. Rove beetles were more effectively sampled using the fenced compared to unfenced pitfall traps.     

D-vac sampling for predatory arthropods in winter wheat

We evaluated the D-vac suction machine for sampling predatory arthropods in Oklahoma winter wheat fields. The efficiency of D-vac sampling was low for adult Coccinellidae and Carabidae. Sampling efficiency was greater for coccinellid larvae. Sampling efficiency was high for adult and immature Nabidae and Chrysopidae, for Araneae, and for adult Staphylinidae. For most predators, there were significant correlations between the number of individuals in D-vac samples and the number of individuals per m² in the field. The highest correlation was 0.82 for adult Staphylinidae. Correlations for most predators were <0.60. Significant partial correlations between D-vac sample estimates and ancillary abiotic and biotic variables occurred for most predators, indicating that D-vac sampling efficiency was affected environmental variables. Multiple regression models were constructed to relate population estimates from D-vac sampling to absolute density by adjusting estimates for influential abiotic and biotic environmental variables. Significant regression models were not achieved for adult Coccinellidae or adult Carabidae, and the coefficient of determination was low (0.18) for the model for adult Nabidae. Higher values of R² were achieved for larval Coccinellidae, Chrysopidae adults and larvae, Nabidae nymphs, Araneae, and adult Staphylinidae. Among abiotic variables, air temperature and wind velocity most frequently entered into step-wise regression models. Among biotic variables, wheat plant growth stage and wheat tiller density frequently entered into models.     

Experimental analysis of the influence of pest management practice on the efficacy of an endemic arthropod natural enemy complex of the diamondback moth

Maximizing the contribution of endemic natural enemies to integrated pest management (IPM), programs requires a detailed knowledge of their interactions with the target pest. This experimental field study evaluated the impact of the endemic natural enemy complex of Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) on pest populations in commercial cabbage crops in southeastern Queensland, Australia. Management data were used to score pest management practices at experimental sites on independent Brassica farms practicing a range of pest management strategies, and mechanical methods of natural enemy exclusion were used to assess the impact of natural enemies on introduced cohorts of P. xylostella at each site. Natural enemy impact was greatest at sites adopting IPM and least at sites practicing conventional pest management strategies. At IPM sites, the contribution of natural enemies to P. xylostella mortality permitted the cultivation of marketable crops with no yield loss but with a substantial reduction in insecticide inputs. Three species of larval parasitoids (Diadegma semiclausum Hellén [Hymenoptera: Ichneumonidae], Apanteles ippeus Nixon [Hymenoptera: Braconidae], and Oomyzus sokolowskii Kurdjumov [Hymenoptera: Eulophidae]) and one species of pupal parasitoid Diadromus collaris Gravenhorst (Hymenoptera: Ichneumonidae) attacked immature P. xylostella. The most abundant groups of predatory arthropods caught in pitfall traps were Araneae (Lycosidae) > Coleoptera (Carabidae, Coccinelidae, Staphylinidae) > Neuroptera (Chrysopidae) > Formicidae, whereas on crop foliage Araneae (Clubionidae, Oxyopidae) > Coleoptera (Coccinelidae) > Neuroptera (Chrysopidae) were most common. The abundance and diversity of natural enemies was greatest at sites that adopted IPM, correlating greater P. xylostella mortality at these sites. The efficacy of the natural enemy complex to pest mortality under different pest management regimes and appropriate strategies to optimize this important natural resource are discussed.     

Influence of Ground Predators on the Survival of the Mediterranean Fruit Fly Pupae, Ceratitis capitata, in Spanish Citrus Orchards

A survey of predaceous ground arthropods was conducted in two citrus orchards in Valencia, Spain, and their role as predators of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) pupae was evaluated under field and laboratory conditions. A total of 2959 predaceous arthropods were collected in pitfall traps in the two orchards from July 2003 to September 2004. Ants (Hymenoptera) were the most abundant group (83.61%), followed by Staphylinidae (7.77%), Araneae (5.24%), Dermaptera (2.13%), Carabidae (0.64%) and Cicindelidae (0.61). Pupae disappearance rates were higher during the warmer months of the year, from May to October, and in the orchard with the largest ant population. In the warm season, the mean survival of C. capitata pupae was 35.7±6.2% and 14.3±6.7%, respectively, in both orchards. Patterns of predation, inferred from broken or abnormal pupae, were more frequently observed in the colder months, from November to April, when spiders, Staphylinidae and other predators were present. In the cold season, the combined effect of predation and low temperature led to an adult emergence rate of 26.7±9.9% and 13.0±7.5% in both orchards. In no-choice laboratory trials, all predator species tested fed at significantly different rates on C. capitata pupae. Preliminary data show that the Carabids, Pseudophonus rufipes (Duftschmid) and Harpalus distinguendus (Degeer), were the most voracious species, consuming more than one pupa per day.     

Arthropods as Bioindicators in Agroecosystems of Jiang Han Plain,Qianjiang City,Hubei China

Using sweeping nets and pitfall traps, arthropods on the soil surface and on vegetation were periodically surveyed in two villages on the Jiang Han Plain from April to September 1994. Statistical analysis of the resulting data delineated groups of bioindicators on vegetation and on the grounds that represent components of formulas for evaluating environmental quality in agroecosystems. These groups are (1) Coccinellidae and Chrysopidae (seasonally migrating predators factor); (2) Braconidae and Chalcidoidea (parasitic insects factor); (3) Araneae and Mantodea on vegetation and Araneae, Carabidae, Opiliones and Nitidulidae on the ground (carnivorous arthropods factor); and (4) Formicidae, Isopoda, and Chilopoda (soil-dwelling arthropods factor). The following resource pools were identified for the different model arthropods: woodlots for Araneae and Mantodea; field margins for Chrysopidae and Coccinellidae; hedgerows for Braconidae and Chalcidoidea; and low-input cropfields on the floodplains for epigeic carnivorous arthropods. Comparison of these insect groups in different rural landscape units demonstrated the importance of a mosaic rural landscape, including woodlots, rationally designed field margins, and cropland, for creating an ecologically favorable agricultural environment.     

Influence of buffalograss management practices on Western chinch bug and its beneficial arthropods

A 2-yr study was conducted to document the influence of selected buffalograss, Buchlo? dactyloides (Nuttall) Engelmann, management practices (three mowing heights and five nitrogen levels) on the seasonal abundance of the western chinch bug, Blissus occiduus Barber (Heteroptera: Lygaeidae), and its beneficial arthropods. Vacuum, pitfall, and sticky traps samples were collected every 14 d from the middle of May through October from western chinch bug-resistant ('Prestige') and -susceptible ('378') buffalograss management plots. In total, 27,374 and 108,908 western chinch bugs were collected in vacuum and pitfall traps, respectively. More than 78% of all western chinch bugs were collected from the highly susceptible buffalograss 378. Significantly more bigeyed bugs (Geocoridae: Geocoris spp.) were collected from the 378 buffalograsss management plots than the Prestige plots. In contrast, buffalograss cultivar had little influence on the abundance of other beneficial arthropods collected. Statistically, western chinch bugs were least abundant at the lowest mowing height (2.5 cm) and increased in abundance with increasing fertility. Numerically, however, differences among management levels on western chinch bug abundance were minimal. Numerous beneficial arthropods were collected from buffalograss management plots, including spiders, predatory ants, ground beetles (Carabidae), rove beetles (Staphylinidae), bigeyed bugs, and several species of hymenopterous parasitoids. In general, beneficial arthropods were essentially unaffected by either mowing height or nitrogen level. Scelionid wasps represented 66.3% of the total parasitoids collected. The total number of scelionid wasps collected among the three mowing heights and five nitrogen levels were approximately equal.     

Hibernation of predatory arthropods in semi-natural habitats

Non-crop habitats provide important resources for natural enemies. Many natural enemies hibernate in non-crop habitats, from which they may colonise arable fields in the spring. Spring colonisation ensures annual repopulation of the crop with natural enemies, allowing them to keep pace with the development of pest populations. The availability of non-crop habitats can, therefore, be crucial to successful conservation biological control. We quantified the density of overwintering natural enemies near organic Brussels sprout crops in five different non-crop habitats (short grassy field margin, herbaceous field margin, herbaceous field margin under a tree line, ditch and forest). Soil and litter samples of non-crop habitats were taken at two sites. One site was located in an open agricultural landscape, the other in a landscape dominated by mixed forest. Insects belonging to Staphylinidae, Araneae, Carabidae, Coccinellidae and Dermaptera were the most abundant. Mean densities of predatory arthropods were higher in the open agricultural landscape (290 predators m⁻²) than in the forested landscape (137 predators m⁻²). Herbaceous habitat types supported the highest densities of overwintering predators (up to 400 predators m⁻²), whereas densities in the forest were lowest (10 predators m⁻²). These results indicate that herbaceous non-crop habitats are important refugia for predators and may play a vital role in conservation biological control. Handling Editor: Arne Janssen.     

Species composition, seasonal dynamics and numerical responses of arthropod predators in organic strawberry fields

The species composition and relative abundance of predatory arthropod fauna were studied in organic strawberry fields in northwestern Turkey using sweep net sampling and pitfall trapping (activity density). Arachnida constituted 13.1 and 11.5% of the sweep net and pitfall trap catches, respectively. Among the predatory insects, the most abundant groups were Heteroptera (26.7%), Diptera (25.9%), Coleoptera (16.9%) and Orthoptera (10.8%) in sweep net samples. Coleoptera (84.2%) dominated the pitfall trap catches. Many aphid specific and polyphagous predators reached peak abundance during June and July. Pearson's two-tailed correlations showed a significant and positive relationship between syrphid, coccinellid or chrysopid predator numbers and strawberry aphid density. Aphid density was not significantly correlated with carabid or with nabid abundance. Examination of spatial distribution patterns of all predatory arthropod groups using Taylor's Power Law indicated that most arthropod predators, except carabids, exhibited aggregated dispersion patterns. Coccinellids changed their spatial patterns from a uniform to an aggregated distribution through the season. There was also a significant linear correlation between Anterastes sp. abundance (larvae+adults) and Isophya rectipennis+Poecilimon ricteri (larvae+adults) density at both locations. We observed, for the first time, Anterastes preying on Isophya and Poecilimon species. The seasonal abundance of the major predatory groups were described, and their potential importance in controlling strawberry aphid and other pests is discussed.     

Organic versus conventional management in an apple orchard: effects of fertilization and tree-row management on ground-dwelling predaceous arthropods

1 Organic and conventional management of apple orchards may have a different effect on arthropod communities.
2 We conducted a 3-year study to assess the effect of two strategies of fertilizer treatment (organic versus chemical) and three tree-row management systems (straw mulching, tillage and herbicide) on activity-density and biodiversity of epigeic predators. Ground beetles (Carabidae), rove beetles (Staphylinidae), ants (Formicidae) and spiders (Araneae) were sampled monthly with pitfall traps in the same apple orchard during 2003, 2004 and 2005.
3 A total of 4978 individuals were collected. Carabids (56.8% of the total catches) were the most abundant taxonomic group, followed by spiders (20.7%), ants (14.8%) and rove beetles (7.7%). Tree-row management had a greater influence on predator catches than fertilizer treatment. Total predator catches were lower under the mulch. Mulching also reduced carabid abundance, but increased staphylinid catches.
4 Tree row management also had a significant effect on biodiversity parameters. Species richness did not significantly differ among treatments for ants, spiders or the total catches, but was higher on herbicide-treated plots for carabids and on mulched plots for staphylinids. Shannon–Wiener's diversity index was significantly greater in the mulched and herbicide treated plots for total predators and carabids. For staphylinids, this index was significantly greater on the mulched plots. Fertilizer application strategy only influenced the species richness of rove beetles, which was greater in the chemically-treated plots.
5 The results showed that a change from conventional to organic fertilizer treatment of apple trees may be performed without differential effects on predator activity-density or biodiversity. However, a change from herbicide treatment to mulching or mechanical weed control may be significant, depending on the taxonomic group.     

Dynamics of the predatory arthropod community in Spanish olive groves

1 A survey of the predatory fauna of olive pests, particularly the olive moth, Prays oleae, was undertaken in Granada, Spain, from May to September 1994–95. 2 At both experimental sites similar patterns of emergence were observed for all predatory species with peaks occurring in June, both in 1994 and 1995. More individuals and species were captured in the morning than in the evening. 3 A weak inverse relationship existed between the mean monthly temperatures and the total number of predators caught. 4 The number of predatory species and of individuals caught at both sites was, respectively, two and three times larger in 1994 than in 1995; This difference is assumed to have been due to the accumulated affect of 6 years of drought. 5 Synchrony between P. oleae and predator phenology was suggested by the coincidental timing of peak predator numbers with the oviposition and subsequent emergence of the most vulnerable stage of the olive moth’s lifecycle, i.e. the flower generation. 6 There were more individuals of ants caught, whilst more spider species were captured than all other groups; predatory Coleoptera and Heteroptera were poorly represented. 7 Ants appeared to have a detrimental affect on the number of all other predators.     

The spatial dynamics of crop and ground active predatory arthropods and their aphid prey in winter wheat

The distribution of aphid predators within arable fields has been previously examined using pitfall traps. With this technique predominantly larger invertebrate species are captured, especially Carabidae, but the technique provides no estimate of density unless mark-recapture is used. However, many other numerically important aphid predators occur in arable fields and relatively little is known about their distribution patterns nor whether they exhibit a density-dependent response to patches of cereal aphids. Identification of the most effective predators can allow management practices to be developed accordingly. In this study, the distribution of cereal aphids and their predators was examined by suction sampling within a field of winter wheat in Devon, UK, along with visual estimates of weed patchiness. Sampling was conducted on four occasions in 1999 across a grid of 128 sample locations. The distribution of 11 predatory taxa from the Carabidae, Staphylinidae and Linyphiidae was examined. Additionally, the total number of aphid predators and a predation index were used in these analyses. Carabid adults and larvae, along with staphylinid larvae showed the strongest aggregation into patches and the most temporal stability in their distribution. Other taxa had more ephemeral distributions as did the cereal aphids. The distribution of carabid larvae was disassociated from the distribution of cereal aphids for the first two sampling occasions indicating biocontrol was occurring. Other predatory groups showed both association and disassociation. Carabid larvae, Bathyphantes and total numbers of Linyphiidae showed a strong correlation with weed cover for two of the sample dates. Cereal aphids were disassociated from weed cover on three sampling occasions.     

Communities of ground‐dwelling arthropods in conventional and transgenic maize: background data for the post‐market environmental monitoring

To verify the validity of concerns about environmental safety of maize expressing insecticidal Cry toxins (referred to as Bt maize), we compared communities of ground beetles (Carabidae), rove beetles (Staphylinidae) and spiders (Araneae) in plots planted either with Bt maize cultivar YieldGard^® or with the non‐transgenic parental cultivar Monumental. Each cultivar was grown on 5 plots of 0.5 ha for three consecutive years. To increase the field load of Cry toxin, the fully grown maize of the first study year was shredded to small pieces that were ploughed into the soil. Arthropods were collected in pitfall traps and determined to the species level. The abundance and species richness of all studied groups greatly varied over the season and between the seasons but without statistically significant differences between the Bt and non‐Bt plots. A single spider species and three ground beetle species dominated in the catches every year, whereas a set of 1–4 most abundant rove beetle species changed every year. Frequently occurring species were typical for most of Europe. The total counts of ground beetles, rove beetles and spiders collected once or twice per season are proposed to serve as bioindicators in the post‐market environmental monitoring (PMEM).     

Niche Occupation by Invasive Ground-Dwelling Predator Species in Canarian Laurel Forests

The distribution and co-occurrence of three groups of carnivorous soil macro-invertebrates (Carabidae, Staphylinidae, Chilopoda) were examined in laurel forests of the western Canary Islands. The species numbers per site decreased from East to West (La Gomera, El Hierro, La Palma) in both, beetles and centipedes. No evidence was found for the ‘diversity-invasibility-hypothesis’ sensu Elton. The number of invasive species per site increased with that of native species in Chilopoda, and was not significant in Carabidae+Staphylinidae. Carabidae and Staphylinidae were combined to form a guild of non-specialized ground-dwelling predatory beetles. The mandible length of adults and larvae was used as an indicator of the preferred food size class to determine the food niche width and niche separation. Two invasive coleopteran species were also examined: Ocypus olens occupied the vacant top predator niche on El Hierro, and Laemostenus complanatus occupied the vacant medium size predator niche on La Palma. Neither of these species was found in laurel forests of any other island where these niches are occupied by autochthonous species, though they are introduced on these islands too. The Chilopoda occurred in the forests with seven invasive and seven native species. Autochthonous and introduced centipedes species of the same size class and group are mutually exclusive.     

The effect of the dung pad fauna on the emergence ofMusca tempestiva [Dipt.: Muscidae] from dung pads in southern France

The emergence ofMusca tempestiva Fallèn, from cow pads in southern France was reduced by a mean of 98% and 96% respectively in nine experiments concluded in 1979 and 1981, by the action of the complete dung fauna. Fauna emerging from dung pads and captured in simultaneous trapping using dung baited pitfall traps consisted of 13 Dipterous species (9 Muscidae, 2 Sepsidae and 2 Sphaeroceridae), 25 Coleopterous species (7 Scarabaeidae, 1 Geotrupidae, 2 Aphodiidae, 3 Hydrophilidae, 12 Staphylinidae), 3 Hymenopterous parasites and 1 species of macrochelid and 2 species of parasitoid mites carried phoretically by the dung beetles. The total number of insects and mites per trap was usually small. The Staphylinidae which included 4Aleochara species of whichAleochara tristits Gravenhorst andA. bipustulata (L.) are known parasitoids of Diptera pupae, and 6 predatory species, were the most abundant insects present. Whilst the overall abundance of insects and mites trapped was relatively low it is probable that the most important factor in the control ofM. tempestiva was the combined influence of the different elements making up the dung pad fauna.     

Change of arthropod abundance in burned forests: Different patterns according to functional guilds

Forest fires are one of the most frequent and important causes of forest disturbances, the occurrence of which is globally increasing due to the effects of climate change. This study aimed to determine the impacts of fire and human activity on arthropod communities in affected forests. Twelve study sites in three burned areas were selected for this study. Intensities of disturbance in the study sites were characterized as follows: Disturbance Degree (DD) 0 (no fire), DD 1 (surface fire), DD 2 (crown fire), and DD 3 (crown fire followed by reforestation). Arthropods were collected using pitfall traps. Fourteen arthropod taxa (families, orders or classes), which are relatively homogeneous in their feeding habits and abundant, were analyzed. Depth of litter layer was selected as an environmental indicator for disturbance intensity, as it decreases linearly as the degree of disturbance increased. Changes of arthropod abundance in response to disturbance differed among functional guilds. As disturbance intensity increased, the abundance of detritivores decreased, but the abundance of herbivores increased. However, the abundance of predators varied between taxa. Formicidae and Araneae increased in disturbed sites, whereas Carabidae and Staphylinidae did not change. The abundance of Thysanura and Diptera was highly correlated with disturbance intensity, and may be suitable as a bioindicator for forest disturbance. Arthropod communities were more heterogeneous in forests of intermediate disturbance.     

Behavioural responses of three linyphiid spiders to pitfall traps

The behaviour of three linyphiid spider species (Araneae: Linyhiidae) towards pitfall traps was investigated in an experimental arena. Capture efficiencies were low with a mean of between 16 and 57 traps being encountered before spiders were caught. Survival time, trap encounter rate, trap entry rate and reactions towards vegetation were all found to be species-specific. These behaviours are considered to affect differentially pitfall trap efficiency and may partially explain the lack of clear relationship between pitfall trap catch and density found in published studies.