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Abstract Transgenic Bt soybean plants have been developed to control insect pests, such as Anticarsia gemmatalis and Chrysodeixis includens. This objective has been achieved successfully; however, recently, some authors claimed that Bt soybean plants have been more susceptible than non-Bt soybean to Bemisia tabaci MEAM1. In addition, it is unknown whether Bt soybean plants infested by B. tabaci become less resistant to target pests. Therefore, this study aimed to evaluate: (i) whether the previous infestation with B. tabaci can compromise Bt and non-Bt soybean resistance to C. includens; (ii) the effects of B. tabaci infestations on Bt and non-Bt soybean plant growth; and (iii) whether B. tabaci feeding reduces contents of chlorophyll and carotenoids of soybean plants. Bt and non-Bt soybean plants pre-infested with B. tabaci showed no changes in resistance to C. includens. Bt soybean plants infested with B. tabaci showed a lower plant height than uninfested plants. Differently, non-Bt soybean plants exhibited no reduction in plant growth due to B. tabaci feeding. Bt soybean plants suffered a reduction in dry matter only under double infestation (B. tabaci and C. includens), while non-Bt soybean plants experienced reduction in dry matter when infested with B. tabaci and C. includens or by C. includens only. B. tabaci feeding did not alter contents of chlorophyll and carotenoids, and perhaps the reduction in plant growth was related to salivary toxins. Concluding, both Bt and non-Bt soybean plants were susceptible to B. tabaci feeding, evidencing necessity of developing soybean cultivars resistant to B. tabaci.

Background: The efficacy of Bt crystal proteins has been compromised due to their extensive utilization in the field. The second-generation Bt vegetative insecticidal proteins could be the best-suited alternative to combat resistance build-up due to their broad range affinity with midgut receptors of insects. Material and results: The codon-optimized synthetic vegetative insecticidal proteins (Vip3Aa) gene under the control of CaMV35S promoter was transformed into a locally developed transgenic cotton variety (CKC-01) expressing cry1Ac and cry2A genes. Transformation efficiency of 1.63% was recorded. The highest Vip3Aa expression (51.98-fold) was found in MS3 transgenic cotton plant. Maximum Vip3Aa protein concentration (4.23 µg/mL) was calculated in transgenic cotton plant MS3 through ELISA. The transgenic cotton plant (MS3) showed one copy number on both chromatids in the homozygous form at chromosome 8 at the telophase stage. Almost 99% mortality of H. armigera was recorded in transgenic cotton plants expressing double crystal proteins pyramided with Vip3Aa gene as contrasted to transgenic cotton plant expressing only double crystal protein with 70% mortality. Conclusions: The results obtained during this study suggest that the combination of Bt cry1Ac, cry2A, and Vip3Aa toxins is the best possible alternative approach to combat chewing insects. [ABSTRACT FROM AUTHOR]

Insects make up the bulk of terrestrial diversity and about half of insect species are herbivores that have direct relationships with their host plants and are the basis of the entire food chain, on which wildlife and humanity depend. Some herbivorous insect traits, such as their spatio-temporal distribution, are especially relevant in the current scenario of global changes, which are more pronounced in high elevation areas, helping to improve the effectiveness of conservation actions. Here we evaluated the influence that different spatiotemporal scales have on three free-feeding herbivorous insect guilds (fluid-feeding, leaf-chewing, and xylophagous insects) in montane forest islands immersed in a grassland-dominated matrix (campo rupestre). We assessed whether species turnover or nestedness was the main component determining both spatial and temporal species composition variation (β-diversity) of the herbivorous insect community. We also checked the temporal effect on herbivorous insect guilds composition between vertical strata. We sampled herbivorous insects during two summers and two winters in 14 forest islands of different sizes and shapes in a natural mountainous fragment located in southeastern Brazil. A total of 6597 herbivorous insects representing 557 morphospecies were sampled, 290 of which were fluid-feeding, 147 leaf-chewing and 120 xylophagous insects. We found a main contribution of time scale in the organization of the herbivorous insect composition sampled in this study, mainly by turnover, with small differences among guilds. Additionally, we could see that climate determined the local variation of species, corroborating that we have a highly variable always-green system over space and time where the understory community varies less in comparison to the canopy community. Our findings suggest that long-term ecological research on herbivorous community structure in relation to climatic variation is a key element for future investigations, which can be decisive for the conservation of herbivorous insect communities. We also suggest that the effects of anthropogenic pressures must be monitored in this system, since these forest islands may serve as warming refuges in a fragmented landscape holding an invaluable diversity of species that, without these old-growth forest reservoirs, would be doomed to disappear.

Why do herbivores, like Coelomera sp., seek to consume leaf tissue of Cecropia pachystachya colonized by Azteca alfari Emery, 1893 if they are at risk of being attacked by these ants? We collected herbivory data (leaf area lost, occurrence of herbivores and expulsion of enemies by A. alfari) in different shifts (times of the day) in 50 C. pachystachya trees (25 uncolonized and 25 colonized by A. alfari). We registered less leaf area lost and less beetle occurrence in colonized plants. Moreover, the proportion of enemies expelled (killed or removed) is more related to the number of ants that were patrolling and attacking the invaders in the tissue than to the total number of ants present in colonized plants due to A. alfari recruitment and behavior. Thus, such herbivores prefer to use tissues of uncolonized plants and tree structures of colonized ones with less active ants given the risk evaluation of encountering a group of aggressive ants. In this way, C. pachystachya needs these ants to cover the plant tissues as much as possible to ensure its protection.

Insect–plant interactions occur in several ways and have considerable environmental and ecological importance. Many feeding strategies have evolved among herbivorous insects, with host–herbivore systems likely being influenced by trophobionts with ants. We investigated how these interactions vary across elevation gradients by evaluating the structure of the herbivorous insect community and ants associated with Baccharis dracunculifolia at three distinct elevations (800, 1100, and 1400 m a.s.l.) on a mountain in southeastern Brazil. Moreover, we evaluated the diversity and specialisation of interactions between herbivores and host plants along the elevational gradient. We sampled herbivores and ants on 60 plants at each elevation (totalling 180 plant individuals). Herbivore species composition differed among elevations, as did interaction diversity and specialisation. Richness and abundance of chewing insects increased with elevation, while β‐diversity among patches of the host plant was higher at the lowest elevation, probably due to the patchy occurrence of B. dracunculifolia. Richness and abundance of sap‐sucking insects were higher at the intermediate elevation, possibly due to local environmental conditions. We observed a positive relationship between ant and herbivore trophobiont richness on B. dracunculifolia. We found that interactions were more specialised and less diverse at higher elevations compared to the lowest elevation. Changes in vegetation and environmental variables shaped species distributions and their ecological interactions along the elevation gradient. Our study demonstrates that increased elevation changes the structure and patterns of interactions of the herbivore insect guilds associated with the host plant B. dracunculifolia. Ant effects depend on the context, the environment, and the species of ants involved, and are essential for the presence of insect trophobionts. [ABSTRACT FROM AUTHOR]

The plant vigour hypothesis (PVH) predicts that females of galling insects preferentially oviposit on the most vigorous plants or plant modules, where their offspring's performance is highest. In the years 1995 to 1998, we evaluated the responses of species of two different guilds, two chewing species, Pantomorus sp. and Naupactus lar (Coleoptera: Curculionidae) and one galling species, Contarinia sp. (Diptera: Cecidomyiidae), to the length of shoots that were assumed to show the vigour of the tropical shrub Bauhinia brevipes (Leguminosae). The abundance of the chewing herbivores was not influenced by shoot length, since attack rates were randomly distributed among shoot length classes. The abundance of Contarinia galls increased with increasing shoot length, as proposed by the PVH. However, when we related the attack rate to unit length of shoot (cm), which denotes the resource availability per unit length, there was no effect of shoot length on Contarinia sp. These data corroborate the idea of a continuum of responses to plant quality, even when different herbivores feed on the same host plant.

Herbivorous insects that have evolved to feed on senescing tissues of plants, or the phloem flowing from those tissues, comprise a distinct sub-guild of the major trophic guilds, the senescence-feeders. Some senescence-feeders have evolved the capacity to accelerate the rate at which the tissues they feed on senesce, thus enhancing the quantity and quality of their food. Other species prolong their access to good food by feeding alternatively on both senescing and flushing tissues. Senescing plant tissues release a poorer quality food more slowly than the rapid inflow to new growth. As a result, senescence-feeders grow more slowly than equivalent flush-feeders. Any environmental stress of a plant that hastens its rate of senescence results in faster growth and higher survival of senescence-feeders. Senescence-feeders therefore succeed best on damaged or stressed plants and frequently reach outbreak levels on drought-stressed trees. If the distinctive ecology of senescence-feeders and the way in which they differ from flush-feeders in their response to the condition of their host plants are to be recognized and understood, it is important to identify species that belong to this separate trophic sub-guild. Such understanding is also necessary if attempts to control or manage their attacks on crops and forests are to succeed. [ABSTRACT FROM AUTHOR]

Recently, strong top-down (consumer) control of cordgrass (Spartina alterniflora) has been demonstrated. Here, we manipulated the densities of cordgrass consumers, acridid grasshoppers (Melanoplus bivittatus and Melanoplus femurrubrum), to examine their impact on cordgrass in the Plum Island Estuary (PIE), MA, USA. After 1 month, there was no detectable effect of grasshopper density on S. alterniflora biomass and grasshoppers at the highest densities (34 individuals per square meter) consumed only ~14% of the standing stock biomass. However, significant impacts of grasshopper density on grazing damage were seen. For example, plant damage and scarring length increased by 160% and 6,156%, respectively, at the highest grasshopper densities relative to exclusion (zero grasshoppers) densities. Plant height was significantly reduced with increasing grasshopper densities, although this may be a function of leaf tip removal instead of reduced plant growth. No other strong consumers of cordgrass (e.g., Littoraria irrorata, Prokelisia marginata) were observed in PIE and we suggest that consumer regulation of cordgrass is weak in this system. [ABSTRACT FROM AUTHOR]

Parasite damage strongly affects dynamics of boreal forests. Damage levels may be affected by climate change, either directly or indirectly through changes in properties of host trees. We examined how herbivore and pathogen damage in Alnus viridis subsp. fruticosa (Rupr.) Nym. depend on leaf morphology and chemistry, tree size, and tree neighborhood. Damage and tree properties were measured in 2003 and 2004 on eight trees at each of 20 sites in Interior Alaska. Damage varied significantly among sites and among trees within sites, but Cartesian distances between sites were not correlated with similarity in damage levels. Compared with middle leaves, terminal leaves experienced less damage from phloem-feeding insects and pathogens, whereas leaf-roller damage was largely confined to terminal leaves. Summer drought in 2004 strongly reduced damage from phloem-feeding insects, while damage from chewing insects increased. Overall, herbivore damage was best explained by leaf morphology and chemistry, and pathogen damage by the proximity of other trees; the two damage types were not correlated with each other. Reproduction was negatively correlated with herbivore damage, but positively with pathogen damage. The contrasting relationships found for individual feeding guilds suggest that they must be studied separately in assessing impacts of climate change on parasite damage. [ABSTRACT FROM AUTHOR]

Insect pests are major problems for all crops, worldwide. In this review we will focus on legumes, which are attacked by a range of insect pests including pod/seed feeders, defoliators and sap feeders. We review the history of breeding for resistance to insect pests in legumes, which has had mixed success, and discuss further opportunities in this area. We also review the extraordinary array of direct and indirect mechanisms contributing to insect defence in legumes, the understanding and exploitation of which offer opportunities for both legume and non-legume crops. There is also good potential to improve insect resistance in legume crops through a detailed understanding of the signaling pathways that regulate induced responses to insect feeding, and recent progress in this area, primarily obtained from non-legume systems, is reviewed. The importance legumes play in farming systems, their wide range of novel chemistry and the emergence of model systems suitable for genomic approaches present opportunities for research in this area strongly linked to breeding programs to help develop legume crops with enhanced insect resistance. [ABSTRACT FROM AUTHOR]

Plant-insect interaction is an important field for studying plant immunity. The beet armyworm, Spodoptera exigua , is one of the best-known agricultural pest insects and is usually used to study plant interactions with chewing insects. Here, we describe a protocol for insect feeding assays with Spodoptera exigua lavae using model host plant Arabidopsis thaliana , which is simple and easy to conduct, and can be used to evaluate the effect of host genes on insect growth and thus to study plant resistance to chewing insects., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (Copyright © 2020 The Authors; exclusive licensee Bio-protocol LLC.)