Arthropod-Plant Interactions最新文献

Several studies on floral nectar demonstrated that the behaviour of visit performed by pollinators is influenced by nectar chemistry. Biogenic amines act as neurotransmitters in invertebrates and recently have been reported in the floral nectar of 15 plant species for the first time. However, both their occurrence in floral nectar and the effects of their nectar-like concentrations on bee behaviour remains largely unsubstantiated. To increase knowledge on the role of biogenic amines on plant–pollinator interactions, here we (i) investigated the biogenic amine composition of Echium vulgare nectar in relation to its floral sexual phases, and (ii) studied how an artificial solution enriched with nectar-like concentrations of tyramine affects the visit on flowers of bumblebees under semi-controlled conditions. The chemical analysis reported the presence of tyramine in E. vulgare nectar and no difference in concentration between the two sexual phases. To explore potential effects of tyramine on bee behaviour, we designed a new method consisting in zucchini flowers emptied of their natural nectar and refilled with artificial tyramine-enriched nectar, and we used bumblebee workers as pollinator model. We found that bees fed tyramine-enriched solution spent less time foraging on a single flower than those fed control solution, suggesting that their behaviour of visit was overall more dynamic. Our results highlight the importance of addressing further investigations on this emerging class of nectar compounds on insect cognition and behaviour, other than on its occurrence and distribution in nectar of other species.

Plant species diversity in agricultural systems has been shown to provide multiple ecological and agronomic benefits. How it affects the soil microbial communities, especially the guild of entomopathogens capable of controlling insect pests, has not been studied. We used the set-up of the “Experimentation in Ecosystem Research”, at Jena, Germany, to study the role of plant species diversity in facilitating insect pest suppressiveness in soils via entomopathogens such as insect-killing fungi (EPF) and nematodes (EPN). The aim was to gain insights for improving the natural control of wireworms and other pests by supporting the levels of pest antagonistic organisms in the soil. Soils were sampled from plots with a fixed number (from zero to 16) of plant species from different functional groups. Samples were baited with mealworm Tenebrio molitor larvae and the mortality (k-factor) was determined. A supplementary study was conducted to relate the findings to a soil pest, wireworm (Agriotes sp.), using potting soil and a high and low dose of entomopathogenic fungi and nematodes. Field-collected wireworms were subjected additionally to a maximum challenge test, using a Metarhizium strain naturally occurring in the soil from which the wireworm larvae were collected. Our results showed that the increase in the number of plant species at the growing site can significantly increase the killing power (k-factor) of the soil. Plots with legumes had significantly higher k-values than plots without. EPF occurred significantly more often in plots with legumes than in plots without. Wireworms survived entomopathogen treatments where all mealworms died, but developed mycosis in the maximum challenge test. These findings need to be incorporated into cropping system design as a component in maximizing ecosystem services via ecostacking.

A novel wireworm ‘probe’ trap is described, characterized, and used in field trials to (i) determine effects of different spring tillage treatments on its efficiency capturing Agriotes obscurus L. Coleoptera: Elateridae wireworms; and (ii) assess its ability to predict crop damage. In pot trials, its attractiveness to other wireworm species was determined. In a forage/grass field, spring tillage treatments included: ploughing, rototilling, glyphosate-sprayed then ploughing, glyphosate-sprayed then rototilling, glyphosate-sprayed untilled, and untilled. The number of wireworms captured in tilled treatments increased until 20 October. The number of wireworms captured in untilled treatments remained low. Subterranean CO₂ levels in tilled treatments decreased after tillage and over the trapping period, suggesting the increase in captured wireworms occurred because trap CO₂ levels were not overwhelmed by soil levels. The decrease in subterranean CO₂ was less pronounced in untilled-glyphosate and relatively unchanged in untilled-no glyphosate, corresponding to the lower number of wireworms captured. In a separate trial determining the trap’s ability to predict crop damage, a 2 m-wide section was rototilled in grass/forage fields in the spring of Year 1. Probe traps assessed wireworm levels in August and October of Year 1 to predict crop damage for potato and corn planted in Year 2. The y-intercept of linear equations suggested that wireworms captured in October better-predicted potato damage and corn emergence although equations were significant only for August. October-captured wireworms ≤ 21 mm in length correlated better with crop damage than larger wireworms. Pot studies revealed the probe trap to also attract A. litigiousus, A. sordidus, A. brevis, and A. ustulatus.

Wireworms cause considerable damage to a wide range of crops, including maize which is susceptible to attack from emergence to the 10 to 12 leaf stages. One control strategy involves limiting the exposure of young maize were performed with granulated cereal-based baits. Then, this work was subsequently pursued and intensified with experiments based on the use of trap plants. These experimental works provided a description of the implementation conditions, e.g. choice of trap plant species, density, and positioning relative to maize seedlings—in which these trap plants can be used for the protection of maize crops against wireworm attacks. The technique that gave the more promising results in our experiments was based on the use of a mixture of wheat and maize as bait plants. Thus, the protection of maize against wireworm attacks has an efficacy of 55 to 60%, close to the level of protection of the chemical products currently available in Europe. This easy-to-use and effective strategy could help farmers reduce the use of insecticides in the future. Our work also allows us to identify the current benefits and weaknesses of this strategy and to propose research directions to optimise its effectiveness and facilitate its implementation by farmers.

Spotted pod borer, Maruca vitrata (F.), is one of the severe threats to grain legumes in the tropics and subtropics owing to its destructiveness and broad host range. It is imperative to look for safer alternatives for its management, such as the utilization of host plant resistance which can be induced upon the exogenous application of jasmonic acid (JA) and salicylic acid (SA). We studied the changes induced in the digestive and detoxifying enzymes of M. vitrata upon its feeding on JA and SA-treated pigeonpea plants in comparison with the untreated plants. Both JA and SA induced a defense response in pigeonpea plants against M. vitrata, which in turn affected the pest’s development and physiology. The effect on the digestive enzymes (amylase, total proteases, elastase, lactate dehydrogenase) and developmental parameters (larval duration, larval weight, pupal weight, pupal percent, adult emergence and adult longevity) of M. vitrata was more pronounced and significant in the plants pre-treated with JA and then infested with M. vitrata after 12 h of JA application, compared to other treatments and untreated plants. The resistant genotype, AL 1747 responded better to the exogenous application of elicitors and M. vitrata infestation than the susceptible genotype MN 1. As a counter-response to induced plant defenses, an increase in the activity of glutathione-S-transferases (GST) and glucose oxidase (GOX) enzymes was observed in M. vitrata. Despite elevating its GOX activity upon elicitor application, the pod borer was unable to overcome the induced pigeonpea defences consequent of elicitor application as was indicated by its reduced larval weight and other biological parameters. SA also altered the activities of digestive and defense-related enzymes in M. vitrata; however, the effect was not as pronounced as JA. Both JA and SA seem to be involved in triggering the pigeonpea defenses and their exogenous application can be utilized to develop sustainable pest management strategies against M. vitrata.

Exogenous application of jasmonic acid (JA) can trigger the induced resistance of plants to herbivores. This study aimed to investigate the genetic variation of 13 cucumber cultivars in response to the exogenous application of JA for inducing resistance to the vegetable leafminer, Liriomyza sativae, in the field. The plants were treated with 0 (control), 10, or 50 μM of JA and exposed to natural infestation by L. sativae. Exogenous application of JA-induced resistance to L. sativae, but its effects varied across the cultivars. The most prominent decrease in plant damage (34.7%), leaf damage (78.2%), and the number of larval mines (58%) were observed in Argeto, 14cu4141, and Aroma with 50 μM JA, respectively. The plants sprayed with JA had more leaf thickness, trichome density, and phenol content compared to control plants. Soheil and Beit Alpha2 had the greatest increase in leaf thickness (89.50%) and trichome density (74.42%) at 10 μM JA, respectively. The highest increase of phenol content (14.70%) was seen in Emparator upon treatment with 50 μM JA. Insect damage showed significant negative correlations with leaf thickness and phenol content. Our results indicate that crop cultivars that respond better to treatment should be determined to use JA in pest management programs.

Conservation Agriculture (CA), which combines three principles, (1) limitation of soil disturbance, (2) its permanent cover and (3) crop diversification, is growing worldwide as a low-input system. By limiting soil disturbance, this farming system provides favourable conditions for the development of soil-dwelling organisms including insect pests. Despite potentially high wireworm densities in CA systems, economic damage to maize crop is rarely observed. In this study, we investigated the long-term influence of three tillage practices of decreasing intensity (mouldboard ploughing, surface tillage and no tillage) on wireworm density to confirm that reducing tillage intensity does increase wireworm density. In addition, we hypothesised that the presence of crop residues can limit damage caused by wireworms by diverting them from the main crop and altering their feeding behaviour. Accordingly, we examined whether covering the soil with a mulch at sowing date or leaving below-ground residues of a cover crop grown before maize sowing can limit wireworm damage on maize compared to leaving the soil bare. This study, using CA systems as a case study, improves our understanding of how cover crop management can help reducing wireworm damage for the following crop and illustrates the interest of manipulating pest feeding behaviour to design promising strategies of Integrated Pest Management.

Characteristics of preferred or alternative host plants can impact the population dynamics of polyphagous insects. Chrysodeixis includens has become an important pest in economically important crops such as sunflower, cotton, soybean, and beans. In the present study, we evaluated the effects of basil cultivars Ocimum basilicum (alternative host) on C. includens. For this, larvae were fed daily with bean leaves (preferred host-control) and five basil cultivars (Maria Bonita, Mr. Burns, Italian Large Leaf, Vermelho Rubi, and Cinnamon). Subsequently, development, survival, pupae body mass, reproductive parameters, and life table parameters of insects were evaluated. The populations of C. includens fed with leaves of the Italian Large Leaf cultivar showed similar performance to the preferential host (beans). The other host plants prolonged the duration of the larval stage and negatively affected the reproductive and demographic parameters of C. includens. Mr. Burns negatively affected the development and reduced the reproductive potential of the insect. The cultivars Maria Bonita, Vermelho Rubi, and Cinnamon had a negative effect on the development and reproductive potential of this insect. The results indicate that basil cultivars have a negative effect on the development, longevity, and reproduction of C. includens. The use of basil host plants may be a safe alternative to be used concomitantly with other strategies for the management of C. includens.

Graphical abstract

Extrafloral nectaries (EFNs) are nectar-secreting plant glands not related to pollination. Several not mutually exclusive hypotheses explain the ecological function of EFNs. We focused on the (1) protection hypothesis, which predicts the attraction of natural enemies by the extrafloral nectar, providing indirect defense to plants against herbivores, and the (2) ant-distracting hypothesis, which predicts the distraction of ants away from sap-sucking herbivores secreting sugary rewards (honeydew). We aimed to test both hypotheses simultaneously to understand the relative ecological roles of EFNs in a model plant from the Brazilian Cerrado. We experimentally manipulated plant groups according to the presence or absence of EFNs and hemipterans during two years of field study (2018 and 2019). We found some support for both hypotheses. Extrafloral nectaries reduced the damage caused by herbivores by attracting predatory ants, although plants with both EFNs and hemipterans showed the highest herbivory reduction in 2018. The presence of neither EFNs nor hemipterans was associated with increased fruit production. The honeydew, which had higher sugar concentrations than the extrafloral nectar, was used by ants for longer periods. However, more than 70% of the ants were observed feeding on the extrafloral nectar instead of honeydew. We suggest that the relatively high quantity of EFNs can compensate for their lower quality and still reduce the number of ants attending and protecting hemipterans, ultimately mitigating plant damage. In summary, EFNs may fit multiple functions depending on the ecological context.

Interactions between species are the driving force behind ecological dynamics within communities. For this reason, community structure has been described as networks of interacting species for over a century. However, the high canopies in forests such as the tropical Amazon pose an additional challenge to understand interactions. The main objective of the present study is to infer the interactions between bees and plants collected in the Carajás National Forest (Eastern Amazon) and its surroundings from the analysis of pollen loads from bee specimens deposited in biological collections and to determine the trophic niches of the evaluated bee species. This study also aims to contribute to the restoration planning of deforested areas in the eastern Amazon by identifying priority plant species that could help in restoring interaction networks. Pollen loads samples were collected from bees deposited in two entomological collections. The samples obtained were prepared according to Erdtman's acetolysis method, and the pollen grains were counted, measured and microphotographed. We found 154 bee-plant interactions. The pollen material identified in the 72 bee samples (51 species; 16 genera) showed 82 pollen types (plant taxa), distributed in 28 families and 54 genera, with 43 fully identified species and three indeterminate pollen types. The amplitudes of the trophic niche indicated that the genera Trigona, Centris and Xylocopa had more diverse diets. This work also emphasizes the importance of understanding the plant species that make up the diets of bees for management, conservation and restoration strategies.