Seedbank control has been the cornerstone of agricultural management practices. Regulating weeds by using their predators, as a weed control strategy, may be a prerequisite of decreasing herbicide use, and has thus attracted much research investigating the possible contribution of both vertebrates and invertebrates as weed seed predators. Carabid beetles are considered as one of the most important invertebrate seed predators in agroecosystems. We aimed at investigating carabid beetle preferences to a single prey type, seeds of Viola arvensis. We measured the consumption of seeds in 28 species of carabid beetles, under controlled experimental conditions. Two main tribes are identified in tested species, Harpalini with 12 species and Pterostichini with ten species. We found no relationships between species body mass and Viola’s seed consumption, nor with the ratio between mandible length and labrum width (ML/LW). However, trends became significant with the ratio ML/LW when restricting these analyses to species that ate at least five seeds. In addition, we detected a positive and significant relationship between consumption rate and occurrence in trapping sessions over the last 3 years. These results are in favor of weed seeds control by carabids. Clear limits of this study are the use of a single seed species and under control conditions. This experimentation calls for additional studies to check for consistencies in consumption against seed species.

We used laboratory and field feeding trials to investigate adult carabidbeetle preferences for three brassicaceous weed species (rapeseed, wildmustard, and field pennycress) that are pests in canola. All carabid speciespreferred seeds of rapeseed most and those of field pennycress least andshowed intermediate preference for wild mustard seeds. Beetles highlypreferred imbibed seeds of all three weed species. Activity–density ofcarabids and mean weed seed removal were highly correlated in field plots ofcanola, with activity–density accounting for 67% of the observed variationin seed removal. Our study indicates that seed consumption among carabids isinfluenced by several factors, including weed species, physiological stateof seeds, and carabid activity–density. Carabid seed predation issignificant in canola agroecosystems; therefore, understanding theseinfluences has implications for ecological weed management.

Indirect effects of insect control strategies on weed populations areimportant to consider when developing robust integrated pest managementstrategies. Weed seed predation rates were investigated in corn managedunder three contrasting treatments based on control practices for cornrootworm: (1) the transgenic crop Cry3Bb Bt corn, (2) the broad-spectruminsecticide tefluthrin, and (3) no insecticide control. This 2-yr fieldstudy conducted near Ithaca, NY, involved quantifying seed loss fromvelvetleaf, common lambsquarters, and giant foxtail in arenas with andwithout vertebrate exclosures. Velvetleaf and giant foxtail were unaffectedby the insecticide treatment; however, average seed predation of commonlambsquarters was lower in both the Bt corn (11.9%) and insecticide-treatedplots (11.8%) compared with control plots (17.5%) that did not receive anyinsecticide. Seed predation of common lambsquarters was not affected by thevertebrate exclosure. Lower seed predation in the transgenic Bt corn andinsecticide treatments was likely due to nontarget effects on carabids(Coleoptera: Carabidae). Although the reduction in seed predation was modestand limited to only one of the three weed species tested, our resultshighlight the need for greater risk assessment that includes the ecosystemservice of weed seed predation when considering insect pest managementoptions.

Postdispersal weed seed predation is a significant source of weed mortalityin agroecosystems. The magnitude of seed predation, however, is variable.Understanding the relative importance of factors driving variability in seedpredation rates will increase the potential utility of seed predation tofarmers. We conducted landscape-scale field experiments to quantify andcompare the effects of space, time of sampling, and habitat on weed seedpredation. Seed predation assays, with and without vertebrate exclosures,measured seed predation rates at spatially explicit sample sites across 8.5ha of crop and noncrop habitats on a diversified organic vegetable farm inMaine. Total and invertebrate seed predation averaged 8% and 3% d−1, respectively. Vertebrate seed predators detected bymotion-sensing cameras included small mammals and birds. A ground beetle, Harpalus rufipes, was highly dominant in pitfall traps,comprising 66% of invertebrate seed predators captured within crop fields.Seed predation was randomly distributed in space. However, time of samplingand habitat were highly significant predictors of seed predation. Variancepartitioning indicated that habitat factors explained more variation thandid time of sampling. Total seed predation was greater in crop and riparianforest habitats than in mowed grass, meadow, or softwood forest. Generally,invertebrate seed predation was greatest at sites with an intermediatedegree of vegetative cover, whereas habitat type was the chief bioticdeterminant of vertebrate seed predation rates. These results suggest covercropping and wetland conservation as practices that may bolster seedpredation rates.

Interest in weed seed predation as an ecological weed management tactic hasled to a growing number of investigations of agronomic and environmentaleffects on predation rates. Whereas the measurements in most of thesestudies have taken place at very short timescales, from days to weeks,measurements at longer timescales (from several months to a year) havegreater relevance to the demographic impact of weed seed predation andpotential contributions from this process to ecological weed management. Ouraim was to quantify the impact of crop phase, within a corn–soybean–wheatcrop sequence, on quarterly and annual seed predation rates of giantfoxtail, giant ragweed, and velvetleaf. The study took place in areas of thenorthern U.S. Corn Belt contrasting in dominant land use: Savoy, IL(2005–2007), where corn and soybean production predominates, and EastLansing, MI (2005–2008), where crop production occurs within an oldfield/forest landscape matrix. Mean annual rates of weed seed predation bythe combined action of invertebrate and vertebrate predators were 31 ± 1.6%for giant ragweed, 37 ± 1.4% for velvetleaf, and 53 ± 1.4% for giantfoxtail. Crop phase had negligible effects upon long-term seed predationrates, accounting for less than 2% of observed variation. Weed species andsite-year, in contrast, contributed 35% and 40%, respectively, of thevariation in cumulative annual seed predation. These results are consistentwith the spatial variability in best management practices seen at spatialscales greater than the county level: weed seed predation appears to be aninherently site-specific phenomenon. New developments in managing weed seedpredation as an ecosystem service are therefore likely to have localrecommendation domains or to be driven by stochastic annual variationrelated to weather or granivore demography.

Ground beetles are postdispersal weed seed predators, yet their role inconsuming buried seeds is not well studied. We conducted greenhouseexperiments to investigate how seed burial affects consumption of weed seeds(volunteer canola) by adult ground beetles (Coleoptera: Carabidae). Seedburial depth influenced seed consumption rates as demonstrated by asignificant interaction between seed burial depth, carabid species, andgender of the carabid tested. We observed higher seed consumption by femalesof all species, and greater consumption of seeds scattered on the soilsurface compared with seeds buried at any depth. However, there was evidenceof seed consumption at all depths. Adults of Pterostichus melanarius (Illiger) and Harpalus affinis(Schrank) consumed more buried seeds than did those of Amara littoralis Mannerheim. Agricultural practices, such as tillage,bury seeds at different depths and based on the results of this study, thesepractices may reduce seed consumption by carabids. Soil conservationpractices that reduce tillage (conservation or zero tillage) will favorgreater weed seed predation due, in part, to the high availability of seedsat the soil surface or at shallow soil depths.

Quantification of the movement of insects at field and landscape levels helps us to understand their ecology and ecological functions. We conducted a meta-analysis on movement of carabid beetles (Coleoptera: Carabidae), to identify key factors affecting movement and population redistribution. We characterize the rate of redistribution using motility μ (L2 T−1), which is a measure for diffusion of a population in space and time that is consistent with ecological diffusion theory and which can be used for upscaling short-term data to longer time frames. Formulas are provided to calculate motility from literature data on movement distances. A field experiment was conducted to measure the redistribution of mass-released carabid, Pterostichus melanarius in a crop field, and derive motility by fitting a Fokker–Planck diffusion model using inverse modelling. Bias in estimates of motility from literature data is elucidated using the data from the field experiment as a case study. The meta-analysis showed that motility is 5.6 times as high in farmland as in woody habitat. Species associated with forested habitats had greater motility than species associated with open field habitats, both in arable land and woody habitat. The meta-analysis did not identify consistent differences in motility at the species level, or between clusters of larger and smaller beetles. The results presented here provide a basis for calculating time-varying distribution patterns of carabids in farmland and woody habitat. The formulas for calculating motility can be used for other taxa.

Forest loss has caused fragmentation and destruction of habitats, and thereby presents serious extinction risk to many endemic species in Madagascar. Among many other arthropod groups, carabid beetles are poorly known in Madagascar as regards their distribution, habitat requirements and taxonomy. The aim of this study is to document community composition, distribution patterns and habitat preferences of carabids in the forest-dominated Ranomafana National Park, south-eastern Madagascar. Carabids were collected by hand and trunk traps from secondary forest, primary forest and nearby village areas. In total, 4314 individuals representing 125 species, including 38 new species, were collected. Almost 70% of the species were recorded in very low abundances. Furthermore, there were only a few species in intermediate abundance classes, while the three most abundant species represented ~36% of the total catch. The carabid community seems to be very species rich, consisting mostly of species in low abundances. A positive correlation was found between abundance and occupancy despite high variation among species distribution patterns. Small population sizes of endemic species with nearby habitat destruction make the species especially vulnerable to extinction and increase the importance of protecting Ranomafana National Park.

Indicators of diversity (population density, relative number of species and evenness) in ground beetles (Carabidae) and rove beetles (Staphylinidae) in upland rice fields were assessed between 1995 and 1999 at Garoua in the Benue valley in North Cameroon. A total of 4369 beetles belonging to 45 carabid species and 2109 beetles belonging to 31 staphylinid species were caught in pitfall traps. Among the carabid beetles, five species Scarites (Orientolobus) lucidus strigiceps Quedenfeldt, Chlaeniostenus denticulatus elatus (Erichson), Lissauchenius venator (LaFerté), Pheropsophus marginatus (Dejean) and Abacetus crenulatus Dejean, in decreasing order, were dominant. In the staphylinid group, Paederus sabaeus Erichson was the most common, followed by Stenus ravus Puthz and Stenus (Mendicus) senegalensis Bernhauer. The Shannon–Weiner and evenness indices varied slightly from year to year. Diversity values remained relatively low among the staphylinid beetles, revealing that rice fields were underpopulated by this group of polyphagous predators. The features of predatory soil-surface beetles and the role they play as an IPM component in West African rice ecosystems are discussed.