Agricultural intensification is known to be one of the main drivers of pollinator decline, in particular because flower resources are often scarce in intensively cultivated landscapes. Agroecological ...practices such as wildflower strips implementation are seen as effective to mitigate this food scarcity by increasing the abundance, diversity and temporal continuity of the flower resources. However, in intensive cropping systems, these practices are often poorly adopted by farmers because of technical and economic barriers. We designed a practice based on the conservation of winter cover crop strips in the middle of spring crops and assessed the value of such undestroyed cover crop strips for the enhancement of pollinator populations, and the conservation of wild bee species. Cover crop strips on farmers’ fields were surveyed and compared to existing herbaceous field margins. Our results showed that within-field cover crop strips are effective in increasing the availability and continuity of flower resources for pollinators. We recorded a higher abundance, richness, taxonomic and functional diversity of bees in the covered crop strips than in the field margins, but no significant effect on hoverflies. Wild bees were supported by the sown flowers of the strips during spring, before the main blooming period of the spontaneous flowers of the field margins, and the combination of sown species of three different botanical families in the strips supported wild bees with different ecological traits, including oligolectic bees. Our findings indicate that this practice can support complementary flower resources, but also highlight the importance of protecting and extending spontaneous plant patches such as field margins for the conservation of rare and specialist bees.
The forecasted 9.1 billion population in 2050 will require an increase in food production for an additional two billion people. There is thus an active debate on new farming practices that could ...produce more food in a sustainable way. Here, we list agroecological cropping practices in temperate areas. We classify practices according to efficiency, substitution, and redesign. We analyse their advantages and drawbacks with emphasis on diversification. We evaluate the potential use of the practices for future agriculture. Our major findings are: (1) we distinguish 15 categories of agroecological practices (7 practices involve increasing efficiency or substitution, and 8 practices need a redesign often based on diversification). (2) The following agroecological practices are so far poorly integrated in actual agriculture: biofertilisers; natural pesticides; crop choice and rotations; intercropping and relay intercropping; agroforestry with timber, fruit, or nut trees; allelopathic plants; direct seeding into living cover crops or mulch; and integration of semi-natural landscape elements at field and farm or their management at landscape scale. These agroecological practices have only a moderate potential to be broadly implemented in the next decade. (3) By contrast, the following practices are already well integrated: organic fertilisation, split fertilisation, reduced tillage, drip irrigation, biological pest control, and cultivar choice.
Intensification of agriculture, with landscape simplification and reduction of natural habitats, is known to contribute to the decline of arthropods. Implementation of agroecological practices and ...infrastructures in current cropping systems is expected to mitigate this biodiversity loss and provide pest regulation through natural enemies. The aim of this study was to assess the efficiency of an undestroyed strip of winter cover crop within maize fields to promote ground-dwelling arthropod spillover and their predation activity into fields. The field survey was carried out in 2019 and 2020 within 12 fields. Monitoring of ground-dwelling arthropod activity-density, richness, and predation rate, as well as slug activity-density, was conducted in the strip, in the cropped area and in a grassy field margin. The results show that activity-density of carabids, spiders, and slugs, and the predation rate were overall higher in the strip than in the cropped area or the field margin. No clear edge effect of the strip on arthropods in the cropped area was found, but predation rate was enhanced closer to the strip. We did not record a negative effect of the strip on the occurrence of slugs within the maize crop. The study shows that a mid-field strip of winter cover crops can be efficient for biodiversity conservation of ground-dwellings predators in agricultural landscapes and provide a potential pest control service in cropped fields.
•Preserved winter cover crop strips in cropped maize fields benefit natural enemies.•Strips do not lead to higher occurrence of slugs in cropped maize.•No clear spillover of ground-dwelling arthropods from strips toward crops was found.•Predation activity in crops increased with decreasing distance from the strips.
•Cultivar mixture was more infested by aphids than the least susceptible cultivar.•Intercrops tended to be less infested by aphids than wheat monoculture.•Combining genetic and species diversity did ...not better than each individual practice.•Wheat yields were reduced in intercropping, but not in cultivar mixtures.
Increasing intrafield plant diversity has been shown to regulate pest populations. Mixing wheat cultivars and intercropping winter wheat and white clover are both promising agroecological practices. On field experiments over two growing seasons, we combined both practices and examined the impact on aphid populations and on wheat production. Results show that combining intra- and interspecific diversity did not outperform each practice individually in reducing aphid populations. Taken separately, intercropping tended to have lower aphid infestation, while it was intermediate in cultivar mixtures. Yearly variation in climatic conditions impacted wheat and clover development, as well as the appearance of aphid peaks. Wheat yields and grain nitrogen content were reduced in intercropping by 10% and 7%, respectively, but not in cultivar mixtures. Our findings suggest that intrafield diversification may regulate wheat aphids to some extent, but combining two diversification practices did not result in an attractive trade-off between pest regulation and wheat production in real farming conditions.
The enhancement of pest regulation service in crops depends for a large part on the capacity of agroecological practices to increase the presence of key species or functional traits in arthropod ...communities within fields.
We investigated the effects of undestroyed strips of winter cover crops in maize fields on carabid community composition, and on the distribution of three ecological traits: diet, wing status and body size.
We found that the community composition and the distribution of ecological traits in the in‐field cover crop strips had commonalities with both adjacent cropped areas and field margins. Some species were recorded mostly or only in the strips indicating that strips could support carabid species and help increase local diversity from the first year of establishment.
The activity‐density of Poecilus cupreus and Pterostichus melanarius was higher in the cropped proximity of the strip, and the body size was influenced by the distance from the strip.
Our results suggest that carabid communities are shaped by the habitat type, but the influence of such agroecological infrastructures on communities of adjacent crops is minor beyond a distance of 10 m. However, overall species abundance was increased and thus potentially provided enhanced pest regulation.
Intercropping, i.e., association of two or more species, is promising to reduce insect populations in fields. The cereal aphid Rhopalosiphum padi, a vector of the Barley yellow dwarf virus PAV ...(BYDV-PAV), represents a major threat for cereal grain production. In this study, we tested the potential of winter barley intercropped with clover to reduce the size of R. padi populations and to lower the BYDV-PAV incidence in fields. We used arenas (i.e., sets of 36 barley plants) intercropped with or without clover plants (at different sown densities). In each arena, a single viruliferous founder, R. padi, (with an alate or a wingless morph) was deposited to introduce aphids and viruses in the experiment. Thirteen days later, the number of aphids in the arena, the percentage of plants hosting aphids and the infection rates were monitored. Data produced through this experimental design showed that clover alters the distribution of the aphid progeny (lower aphid spread) produced by an alate founder morph. Moreover, clover reduces the size of aphid populations produced by a wingless founder morph. However, despite the effects of clover on biological parameters of R. padi, the presence of clover in barley arena did not modify BYDV infections, suggesting complex mechanisms between partners of the BYDV pathosystem for plant-to-plant virus spread.
Increasing intrafield plant diversity has been shown to regulate pest populations in various agroecosystems. Among the suggested mechanisms for this bottom‐up pest control, the disruptive crop ...hypothesis states that herbivores' abilities to locate and colonize their host plants are reduced by the presence of non‐host plants. Under laboratory conditions, we evaluated how intercropping wheat and legumes modifies the behaviour of apterous cereal aphids, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), in terms of host plant location and population growth. We compared two intercropping systems – soft winter wheat, Triticum aestivum L. (Poaceae), associated with winter pea, Pisum sativum L., or with white clover, Trifolium repens L. (both Fabaceae) – and sole stands of soft winter wheat. Aphids needed more time to locate their wheat host plant and then spent less time on wheat when it was intercropped with clover. At the population level, and accounting for host plant biomass, only intercropping wheat with clover significantly reduced aphid densities on wheat, as this was particularly disruptive to S. avenae behaviour and population growth. Our laboratory study points out that the species used as non‐host plants and their density are important parameters that should be taken into account in field studies on intercropping systems.
Intercropping cereal and legumes has been shown to regulate pest populations in various agroecosystems. Abilities of apterous cereal aphids, Sitobion avenae (Hemiptera: Aphididae), to locate and colonize their wheat host plants are reduced in wheat–clover intercrops, but not in wheat–pea intercrops. At the population level, and accounting for host plant biomass, only intercropping clover with wheat significantly reduced aphid densities.
Acclimation to a particular environment may provide organisms with advantages in that environment. In species with multiple generations per year, acclimation may cause life‐history traits to vary ...with season and between generations. We investigated flight performance, lifetime egg production, and longevity in relation to the temperature experienced during development and adulthood in the invasive moth pest Grapholita molesta (Busck) (Lepidoptera: Tortricidae). We found that females that developed at low temperature had good flight abilities when they were flown at low, intermediate, and high temperatures. At high temperature, females that developed at high temperature did not outperform females that developed at low temperature. Flight performance was generally poor at low ambient temperature. Our findings suggest a beneficial acclimation effect, occurring at low temperature. Nonetheless, there were potential costs of development at low temperature: development took longer, resulting in smaller females, which laid fewer eggs. Given temporal and spatial temperature variability in the field, dispersal potential should not be considered homogeneous within populations or across generations. Our results suggest that the most favourable time periods for female dispersal are at the beginning and towards the end of the host crop growing season, which has potential implications for monitoring the occurrence and range expansion of this invasive pest species.
1. Generalist predatory insects that exploit unpredictable and ephemeral prey should allocate metabolic resources differently to soma and gonads than specialist species. As the former have more ...opportunities to encounter a wide array of prey than specialists, the expectation is that they will more rapidly resorb oocytes when food is scarce. By doing so, they reallocate resources to the soma to support the search for oviposition sites of a better quality. Similarly, they are expected to resume oogenesis faster than the specialist when good conditions return. 2. This hypothesis was tested by comparing a generalist and a specialist ladybird species belonging to the same genus. 3. A resorption index was calculated for females of both species subjected to several starvation regimes. This index indicated that over a period of fasting of 3 days, the intensity of resorption was greater in the generalist than the specialist. When food was again supplied, oogenesis resumed and within 1 day was faster in the generalist than in the specialist. 4. As predicted, the resorption of oocytes and replenishment occurred faster in the generalist than in the specialist species. This is the first time, to our knowledge, that the speed and intensity of the ovarian dynamics of a predatory insect have been linked to its way of life.
Egg dumping by predatory insects FERRER, AURELIE; CORBANI, AUDE C; DIXON, ANTHONY F. G ...
Physiological entomology,
September 2011, Letnik:
36, Številka:
3
Journal Article
Recenzirano
Synovigenic insects resorb oocytes when food is scarce and mature oocytes when food is plentiful. These two antagonistic processes allow an optimal allocation of resources to reproduction and somatic ...functions. Unlike hymenopteran parasitoids, ladybirds cannot resorb mature oocytes present in the oviducts. Is the energy contained in these oocytes lost or is there a mechanism for recovering it when needed? Females of two species of ladybird beetles Adalia bipunctata (L.) and Adalia decempunctata (L.) that are starved for >24 h lay single infertile eggs, which they immediately eat, and these eggs comprise the mature oocytes in the oviducts at the onset of starvation. This behaviour has some similarities to egg dumping reported in herbivorous insects and is part, in ladybird beetles, of a process to retrieve energy invested in reproduction. Such behaviour may exist in other predatory synovigenic insects species that do not invest in maternal care.
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