Arthropod-Plant Interactions最新文献

Dead-end trap crops are plants used in pest management that are highly attractive to egg-laying adults but do not support the survival of the developing offspring. For the diamondback moth (DBM; Plutella xylostella), Barbarea vulgaris and B. verna (upland cress) are proven dead-end trap crops but the evidence for Lepidium sativum has been contradictory with one study claiming dead-end effects but others showing that it is a suitable host. Since glucosinolate and saponin levels, which, respectively, stimulate oviposition and act as deterrents, vary with plant age in Barbarea spp., the goal of the present study was to investigate the effects of plant age on the attractiveness and dead-end properties of upland cress and two cultivars of L. sativum (garden cress and broadleaf cress). When given the opportunity to lay eggs on the putative dead-end trap crops or cabbage (Brassica oleracea), DBM did not preferentially lay eggs on garden cress and upland cress until the plants were 5 weeks or older, while broadleaf cress was attractive at all ages. Egg-to-adult survival and growth rate on garden cress and broadleaf cress was as high or higher as on cabbage, regardless of plant age. Upland cress did not reduce survival of DBM at 2 and 5 weeks old but did at 10 weeks old. We confirm that plant age is critical to the effectiveness of upland cress as a dead-end trap crop and conclude that garden cress and broadleaf cress can be suitable trap crops but exhibit no dead-end properties.

Fear associated with perceived predation risk can elicit behavioral and physiological changes in animals, including insects. Diamondback moth (DBM), Plutella xylostella, larvae are known to wriggle violently backwards and even fall off plants when attacked by predators and parasitoids. In the laboratory, the DBM larvae exposed to the specialist parasitoid Diadegma insulare were found to move to lower quality, older foliage, which negatively affected their development. In Hawaii, by far the dominant parasitoid species of DBM is the generalist Cotesia vestalis, with many sampling efforts often only yielding this species. Thus, in this study, we investigated the influence of C. vestalis on the behavior of DBM larvae. We focused on the distribution of DBM on cabbage plants, from the youngest to oldest leaves (leaf position 1–12, respectively), in the presence of C. vestalis in the lab and field. We found that in the lab, DBM larvae showed a clear preference for younger leaves (leaf positions 3–5). However, when C. vestalis was present, regardless of whether the parasitoids could touch the DBM, larvae were less likely to be on those preferred leaf positions. This change in larval distribution was also replicated when potted cabbage plants containing DBM larvae were placed in cabbage fields. Changes in herbivore feeding sites, whether mediated by natural enemies or other environmental factors, could have significant implications, not only for herbivore fitness, but also for economic damage to crops based on the value of plant parts affected.

Planting crops to push or pull pests from a main crop and floral enhancements to attract natural enemies are emerging as pivotal agroecological strategies to shift away from synthetic pesticides. The brassica, Lobularia maritima, has great potential to act as a floral enhancement as it is attractive to many insects and improves the fitness of and biocontrol services provided by multiple natural enemies. It has been mainly deployed as an insectary plant; few studies have been conducted on its use as a trap plant. We explored the potential of L. maritima as a targeted flower enhancement in sheltered cropping systems through three case studies: (1) as flower strips alongside a cucumber crop, (2) as flower strips alongside a strawberry crop in a replicated on-farm experiment, and (3) as hanging pots under strawberry cultivation gutters. We monitored beneficial and pest insects in flowers and crops and assessed crop damage. Lobularia maritima stands out as an excellent floral enhancement plant due to its ease of cultivation and its ability to flower consistently over an extended period. Generalist predatory bugs, such as Orius laevigatus and Macrolophus pygmaeus, had higher densities on L. maritima than on other flowers grown next to strawberries. We found more thrips on L. maritima and less thrips on crops in two out of three experiments, compared with controls. Further research is needed to confirm if L. maritima is an effective trap crop for thrips and other pests and to detect possible dis-services, such as the attraction of phytophagous bugs.

Heat stress will be an increasing problem for plants and pollinators. Some Romneya coulteri flowers self-shade reproductive parts with vertically oriented petals; this keeps pistils 3–8 °C cooler. A previous study conducted outside of the plant’s native range found that self-shading flowers experienced higher seed set than flowers with petals that were experimentally forced to all be horizontal (open) or vertical (shaded). Hand-pollinated flowers had higher seed set which negated the effect of petal orientation, suggesting that insect pollination may have driven seed set. In this study, we observed insect visitors and their effects on seed set in R coulteri’s native range. Plant performance was again limited by pollen such that experimentally adding outcross pollen increased seed set. Native and introduced bees showed no proclivity toward either petal orientation. However, the most common visitor, a native beetle (Lytta auriculata), was strongly biased toward approaching and ultimately accepting flowers with vertical petals that provided shade. Beetles were covered with R. coulteri pollen. Flowers bagged with only beetles for 24 h produced as many seeds as controls left open to all visitors. However, beetles also consume pollen and chew petals. Flowers with vertical petals received more beetle damage and damaged flowers produced 35% fewer seeds than those without chewed petals. Despite the potential role of beetles as pollen vectors, flowers with vertical petals did not experience higher seed production. The outcome of beetle visitation on seed set is likely context-dependent. Petals that affected microclimate were attractive to at least one potential pollinator.

Landscape heterogeneity may affect components of biodiversity, including pollinators and the ecosystem function they perform. Landscape heterogeneity may also affect pollinator movement and pollen and gene flow. We assessed how changes in landscape compositional heterogeneity generated by agricultural activities affect the pollen transport service provided by insect pollinators. In eleven agricultural fragments with different landscape heterogeneity, we caught pollinators foraging on flowers and extracted their body pollen loads, discriminating among crop, native, and exotic spontaneous plants. At a local scale, the fragments corresponded to 1-ha plots under agricultural management, or to restored plots without agriculture. The landscape heterogeneity of each fragment was characterized using centered circular areas with different diameters (300, 600, and 1000 m). We then calculated the Shannon Diversity Index as a landscape compositional heterogeneity estimator and using the different landscape patches identified (semi-natural pastures, field crops, woodlands, among others). Through generalized linear mixed models, we found that the amount of pollen transported by individual pollinators was positively related with landscape heterogeneity for all pollen grain categories, but the slope exhibiting a notably sharper incline for crop plant species. In addition, crop pollen load carried by individual pollinator was lower than native and exotic spontaneous pollen, highlighting the importance of these species in agroecosystems. Our findings indicate that increasing landscape heterogeneity can enhance pollen transport, especially from crops and exotic plants. However, to ensure the sustainability of pollination services and agroecosystem functions, it is crucial to protect native plant species and encourage their growth on crop edges, thereby improving agroecosystem conservation.

Zingiberene is an allelochemical found in wild Solanum species and plants resulting from crosses between these and S. lycopersicum. This sesquiterpene is known to reduce the performance of pest herbivores. Diabrotica speciosa has been identified as a potential tomato pest in important producing regions in Brazil, causing damage to leaves and fruits. Therefore, in this study, we investigated how zingiberene, found in advanced tomato genotypes, can affect the food preference, oviposition and longevity of South American corn rootworm, D. speciosa. The feeding behavior of adults was evaluated in bioassays with and without choice. Additionally, a damage scale for tomato plants was constructed to estimate consumption levels in each genotype. Longevity data and the number of eggs deposited on leaflets were obtained from females kept in cages and fed with tomato leaves from each genotype individually. High levels of zingiberene affected the host selection behavior for feeding and the number of eggs deposited by D. speciosa, so that high levels of the compound increased mortality and reduced adult oviposition, which implies the first record of the action of this compound on this insect. These results can guide breeding programs to obtain genotypes that express high levels of zingiberene, which will present greater resistance to the insect, reducing insecticide applications.

Graphical abstract

Summary of the effects of high levels of zingiberene in tomato plants (Solanum spp.) on the biological and behavioral aspects of Diabrotica speciosa (Coleoptera: Chrysomelidae).Ali et., 2019; Rakha et al. 2017; Zeist et al. 2019a, b; Oliveira et al. 2020.

Recent developments in insect science and technology and integrated pest management (IPM) are laying a concrete path for transition from the dreaded chemical-based pest management to biological and biorational-based methods. Herbivore-induced plant volatiles (HIPVs) play an important role in host plant–herbivore–natural enemy interactions and have the potential to enhance the effectiveness of biological and biorational-based controls for integrated pest management (IPM). Synthetic HIPV blends can potentially improve the foraging behavior of predators by attracting them. This study was conducted to explore the emission of plant volatiles under infestation by cotton aphids, Aphis gossypii Glover, and their influence on attraction response of predatory six-spotted ladybird beetle, Cheilomenes sexmaculata (Fab.). Cotton leaf extracts were analyzed by gas chromatography coupled mass spectrometry (GC–MS), and the response of C. sexmaculata to the various extracts was assessed with a Y-tube olfactometer. By comparing the volatile profile of aphid-infested leaf extract with that of uninfested leaf extract, three compounds, namely 3-carene, pentadecane, and α-linolenic acid, were identified as aphid-induced HIPVs. However, the abundance of the other three compounds, heptane, 3-hexenal, and α-copaene significantly increased upon aphid infestation. At a concentration of 5%, aphid-infested leaf extract had the greatest effect on both female (85.9 ± 7.6%) and male (80.9 ± 6.4%) beetles. These results confirmed that HIPVs induced by aphids in cotton could attract C. sexmaculata beetles. Future tests need to be conducted to determine which compounds could be exploited as attractants for C. sexmaculata.

Understanding the factors that signal plant and pollinator phenologies is important for assessing the potential impacts of climate change. However, limited information is available on how well bees track preferred host plants over time and how traits like body size may govern differential responses among species, particularly in xeric areas where floral resources and climate are unpredictable. We studied the nesting phenology of six solitary, cavity-nesting bees that differ in host breadth and body size in the Monte Desert ecosystem, Argentina, over nine consecutive years. We used cross-correlation analysis to assess if the ability of bees to track the flowering phenology of their host plants and abiotic environment, as well as to detect potential differences between specialist and generalist bees. We found that nesting phenology is predicted by multiple flowering and climatic variables regardless of the bees’ level of specialization, and that there is a differential pattern in body size. The nesting phenology of smaller bees was predicted by the number of individuals in bloom, indicating some spatial pattern in resource availability. While the nesting phenology of some bees was predicted by flowering variables alone, that of other bees was explained by a combination of flowering and climatic variables. Our study also indicated that the inter-annual variability of nesting was greater in generalist bees than in specialist bees. These results suggest that if phenological decoupling occurs, bees might be able to restore it by detecting multiple environmental signals, and that generalist bees might be more vulnerable than previously expected.

Lygus bugs (Hemiptera: Miridae) can damage economically important crop plants by feeding on their active growing points, such as the apical meristem and buds, and reproductive organs, such as flower buds, flowers, seeds, and fruits. Plant injury is a combination of mechanical damage by the stylet and the effects of saliva, which contains enzymes that break the plant cells. On some occasions, oligophagous Lygus species can act as biocontrol organisms when predating on eggs and larvae of pest insects. This review summarises studies where trap crops have been used to control Lygus bug populations on various crops and to reduce damage to crops. We also focus on the factors that affect the host plant and habitat selection of the highly polyphagous Lygus bugs and discuss the reasons why a less favourable host plant in the laboratory might become attacked by Lygus bugs in the field. An analysis of rapidly developed worldwide Lygus damage problems in conifer nurseries in the late 1970s and early 1980s is presented as an example of how rapidly Lygus bugs can adapt to changes in environmental conditions and new types of crops. We suggest that the rate of crop irrigation and the efficiency of weed control could be factors augmenting Lygus populations and the severity of Lygus damage. These factors should also be considered in the planning of trap crop strategies for Lygus spp.