Field-Evolved Sulfoxaflor Resistance of Three Wheat Aphid Species in China

Sulfoxaflor belongs to a new class of insecticides which are effective against many sap-feeding pests. Sitobion miscanthi, Rhopalosiphum padi, and Metopolophium dirhodum are the predominant pests coexisting on wheat plants. It is unknown whether these aphid species have developed resistance to sulfoxaflor. Here, the susceptibilities of three wheat aphid species from different regions of China to sulfoxaflor were evaluated. The results showed that two S. miscanthi, one R. padi, and two M. dirhodum field populations were highly resistant to sulfoxaflor. Additionally, 13 S. miscanthi, 9 R. padi, and 4 M. dirhodum field populations were moderately resistant to sulfoxaflor. Analysis of differences in toxicity showed that the susceptibility levels of R. padi in 9 of 20 regions, M. dirhodum in 5 of 9 regions, and M. dirhodum in 3 of 9 regions to sulfoxaflor were greater than those of S. miscanthi, S. miscanthi, and R. padi in the same regions, respectively. Thus, each wheat aphid species has field populations that are highly sulfoxaflor resistant. The R. padi and M. dirhodum populations were more susceptible to sulfoxaflor than those of S. miscanthi. These findings provide new insights into insecticide resistance development and rational sulfoxaflor use.

Urban human-wildlife conflict: North Island kākā (Nestor meridionalis septentrionalis) in Wellington City

<p>Human-wildlife conflict is common wherever humans and wildlife coexist and is a growing problem in urban landscapes. Successfully mitigating conflict with wildlife requires an understanding of the ecological and social dimensions of the problem. In Wellington City, New Zealand, a human-wildlife conflict is beginning to emerge with North Island kākā (Nestor meridionalis septentrionalis: Nestoridae), a threatened endemic parrot that was reintroduced to the city in 2002. Kākā damage property but especially damage tree bark while foraging for sap. In this thesis, I investigate the conflict with kākā using ecological, behavioural and social science approaches to understand the problem and recommend ways to mitigate the growing conflict with kākā. To investigate tree selection for sap foraging by kākā, I sampled the characteristics, microhabitat and distribution (independent variables) of 282 trees at 15 sites across public greenspaces in Wellington City, and used model averaging to determine the relative influence of independent variables on the binary dependant variable – presence/absence of bark damage. Tree size (Σωᵢ [Akaike weight] = 0.859) and site exposure (Σωᵢ = 0.739) had the greatest influence on tree selection for sap feeding. Kākā were found to prefer larger trees ( x ± SE, DBH: x damaged = 64.8 ± 5.2 cm, x undamaged = 32.9 ± 4.5 cm) at more exposed sites. Exotic species were significantly more likely to have been damaged than native species (Fisher’s exact test, p < 0.001). Seven of 10 tree species damaged were exotic, and exotic conifers, such as macrocarpa (Cupressus macrocarpa) and Lawson cypress (Chamaecyparis lawsoniana) were the most commonly damaged species. I used instantaneous scan sampling to record kākā behaviour during 25 60-100 minute observation periods at Anderson Park, Wellington Botanic Garden, and during 12 opportunistic observations of sap feeding kākā in Wellington City during other research activities. Forty observations of sap feeding were made and 20 sap feeding kākā identified. Based on estimated sex, females were no more likely to sap feed than males (exact binomial test p = 0.916) and both adults and juveniles were observed sap feeding. Kākā were observed displacing sap-feeding conspecifics and defending sap feeding sites from tui (Prosthemadera novaeseelandiae). This indicates that sap is an important resource across sexes and life stages of kākā and is not just a supplementary food for females before breeding as previously hypothesised. Since supplementary food is provided by Karori Wildlife Sanctuary and utilised by the identified kākā, and 34% of Wellington residents provide food and water for birds, it is unlikely that further provision of supplementary food will reduce sap feeding. To investigate residents’ attitudes and problems with birds, I hand-delivered 1030 questionnaires to households in 10 Wellington City suburbs. I then assessed the relationship between a person’s attitude and their biodiversity knowledge, engagement with birds and greenspaces and experience of bird problems. An extraordinary survey return rate of 61.8% (n = 635) revealed that residents had overwhelmingly positive attitudes towards native birds, despite 25% experiencing a bird problem. Planting trees to attract birds was the only predictor to provide substantial inference for attitude (ωi = 0.873). Experiencing a problem with birds was not an influential predictor of attitude when modelled alone (ΔAIC = 17.50, ωi = 0.000), but when combined additively (ωi = 0.568) and interactively (ωi = 0.400) with planting to attract birds these models comprised the confidence set. Respondents who had planted to attract birds were more likely to have more positive attitudes than the rest of the population even when they reported a bird problem. Hence, attitude to birds and tolerance of problems they cause was most closely associated with a person’s positive engagement with birds rather than their negative experiences.</p>

Urban human-wildlife conflict: North Island kākā (Nestor meridionalis septentrionalis) in Wellington City

<p>Human-wildlife conflict is common wherever humans and wildlife coexist and is a growing problem in urban landscapes. Successfully mitigating conflict with wildlife requires an understanding of the ecological and social dimensions of the problem. In Wellington City, New Zealand, a human-wildlife conflict is beginning to emerge with North Island kākā (Nestor meridionalis septentrionalis: Nestoridae), a threatened endemic parrot that was reintroduced to the city in 2002. Kākā damage property but especially damage tree bark while foraging for sap. In this thesis, I investigate the conflict with kākā using ecological, behavioural and social science approaches to understand the problem and recommend ways to mitigate the growing conflict with kākā. To investigate tree selection for sap foraging by kākā, I sampled the characteristics, microhabitat and distribution (independent variables) of 282 trees at 15 sites across public greenspaces in Wellington City, and used model averaging to determine the relative influence of independent variables on the binary dependant variable – presence/absence of bark damage. Tree size (Σωᵢ [Akaike weight] = 0.859) and site exposure (Σωᵢ = 0.739) had the greatest influence on tree selection for sap feeding. Kākā were found to prefer larger trees ( x ± SE, DBH: x damaged = 64.8 ± 5.2 cm, x undamaged = 32.9 ± 4.5 cm) at more exposed sites. Exotic species were significantly more likely to have been damaged than native species (Fisher’s exact test, p < 0.001). Seven of 10 tree species damaged were exotic, and exotic conifers, such as macrocarpa (Cupressus macrocarpa) and Lawson cypress (Chamaecyparis lawsoniana) were the most commonly damaged species. I used instantaneous scan sampling to record kākā behaviour during 25 60-100 minute observation periods at Anderson Park, Wellington Botanic Garden, and during 12 opportunistic observations of sap feeding kākā in Wellington City during other research activities. Forty observations of sap feeding were made and 20 sap feeding kākā identified. Based on estimated sex, females were no more likely to sap feed than males (exact binomial test p = 0.916) and both adults and juveniles were observed sap feeding. Kākā were observed displacing sap-feeding conspecifics and defending sap feeding sites from tui (Prosthemadera novaeseelandiae). This indicates that sap is an important resource across sexes and life stages of kākā and is not just a supplementary food for females before breeding as previously hypothesised. Since supplementary food is provided by Karori Wildlife Sanctuary and utilised by the identified kākā, and 34% of Wellington residents provide food and water for birds, it is unlikely that further provision of supplementary food will reduce sap feeding. To investigate residents’ attitudes and problems with birds, I hand-delivered 1030 questionnaires to households in 10 Wellington City suburbs. I then assessed the relationship between a person’s attitude and their biodiversity knowledge, engagement with birds and greenspaces and experience of bird problems. An extraordinary survey return rate of 61.8% (n = 635) revealed that residents had overwhelmingly positive attitudes towards native birds, despite 25% experiencing a bird problem. Planting trees to attract birds was the only predictor to provide substantial inference for attitude (ωi = 0.873). Experiencing a problem with birds was not an influential predictor of attitude when modelled alone (ΔAIC = 17.50, ωi = 0.000), but when combined additively (ωi = 0.568) and interactively (ωi = 0.400) with planting to attract birds these models comprised the confidence set. Respondents who had planted to attract birds were more likely to have more positive attitudes than the rest of the population even when they reported a bird problem. Hence, attitude to birds and tolerance of problems they cause was most closely associated with a person’s positive engagement with birds rather than their negative experiences.</p>

Common resistance mechanisms are deployed by plants against sap-feeding herbivorous insects: insights from a meta-analysis and systematic review

Sap-feeding insects cause significant yield losses to the worlds crops, these insects feed using syringe-like mouthparts and electrophysiology can be used to compare feeding behaviour on susceptible and resistant plants to identify the mechanistic processes behind resistant phenotypes. Data extracted from 129 studies, comprising 41 insect species across eight insect taxa and 12 host-plant families representing over 30 species, demonstrates that mechanisms deployed by resistant plants have common consequences on the feeding behaviour of diverse insect groups. We show that insects feeding on resistant plants take longer to establish a feeding site and have their feeding duration suppressed two-fold compared with insects feeding on susceptible plants. Our results reveal that the underlying traits contributing towards resistant phenotypes are conserved across plant families, deployed against taxonomically diverse insect groups, and that the underlying resistance mechanisms are conserved. These findings provide new insight that will be beneficial when developing future crop varieties.

Screening Candidate Effectors of the Bean Bug Riptortus pedestris by Proteomic and Transcriptomic Analyses

The damage of Riptortus pedestris is exceptional by leading soybean plants to keep green in late autumn. Identification of the salivary proteins is essential to understand how the pest-plant interaction occurs. Here, we have tried to identify them by a combination of proteomic and transcriptomic analyses. The transcriptomes of salivary glands from R. pedestris males, females and nymphs showed about 28,000 unigenes, in which about 40% had open reading frames (ORFs). Therefore, the predicted proteins in the transcriptomes with secretion signals were obtained. Many of the top 1,000 expressed transcripts were involved in protein biosynthesis and transport, suggesting that the salivary glands produce a rich repertoire of proteins. In addition, saliva of R. pedestris males, females and nymphs was collected and proteins inside were identified. In total, 155, 20, and 11 proteins were, respectively, found in their saliva. We have tested the tissue-specific expression of 68 genes that are likely to be effectors, either because they are homologs of reported effectors of other sap-feeding arthropods, or because they are within the top 1,000 expressed genes or found in the salivary proteomes. Their potential functions in regulating plant defenses were discussed. The datasets reported here represent the first step in identifying effectors of R. pedestris.

Microbe Profile: Xylella fastidiosa – a devastating agricultural pathogen with an endophytic lifestyle

Xylella fastidiosa is a vector-borne plant vascular pathogen that has caused devastating disease outbreaks in diverse agricultural crops worldwide. A major global quarantine pathogen, X. fastidiosa can infect hundreds of plant species and can be transmitted by many different xylem sap-feeding insects. Several decades of research have revealed a complex lifestyle dependent on adaptation to the xylem and insect environments and interactions with host plant tissues.

Uncovering Symbionts Across the Psyllid Tree of Life and the Discovery of a New Liberibacter Species, “Candidatus” Liberibacter capsica

Sap-feeding insects in the order Hemiptera associate with obligate endosymbionts that are required for survival and facultative endosymbionts that can potentially modify resistance to stress, enemies, development, and reproduction. In the superfamily Psylloidea, the jumping plant lice (psyllids), less is known about the diversity and prevalence of their endosymbionts compared to other sap-feeding pests such as aphids (Aphididae). To address this knowledge gap, using 16S rRNA sequencing we identify symbionts across divergent psyllid host lineages from around the world. Taking advantage of a new comprehensive phylogenomic analyses of Psylloidea, we included psyllid samples from 44 species of 35 genera of five families, collected from 11 international locations for this study. Across psyllid lineages, a total of 91 OTUs were recovered, predominantly of the Enterobacteriaceae (68%). The diversity of endosymbionts harbored by each psyllid species was low with an average of approximately 3 OTUs. Two clades of endosymbionts (clade 1 and 2), belonging to Enterobacteriaceae, were identified that appear to be long term endosymbionts of the psyllid families Triozidae and Psyllidae, respectively. We also conducted high throughput metagenomic sequencing on three Ca. Liberibacter infected psyllid species (Russelliana capsici, Trichochermes walkeri, and Macrohomotoma gladiata), initially identified from 16S rRNA sequencing, to obtain more genomic information on these putative Liberibacter plant pathogens. The phylogenomic analyses from these data identified a new Ca. Liberibacter species, Candidatus Liberibacter capsica, that is a potential pathogen of solanaceous crops. This new species shares a distant ancestor with Ca. L. americanus, which occurs in the same range as R. capsici in South America. We also detected the first association between a psyllid specializing on woody hosts and the Liberibacter species Ca. L. psyllaurous, which is a globally distributed pathogen of herbaceous crop hosts in the Solanaceae. Finally, we detected a potential association between a psyllid pest of figs (M. gladiata) and a Ca. Liberibacter related to Ca. L. asiaticus, which causes severe disease in citrus. Our findings reveal a wider diversity of associations between facultative symbionts and psyllids than previously reported and suggest numerous avenues for future work to clarify novel associations of ecological, evolutionary, and pathogenic interest.

Transitional genomes and nutritional role reversals identified for dual symbionts of adelgids (Aphidoidea: Adelgidae)

Many plant-sap-feeding insects have maintained a single, obligate, nutritional symbiont over the long history of their lineage. This senior symbiont may be joined by one or more junior symbionts that compensate for gaps in function incurred through genome-degradative forces. Adelgids are sap-sucking insects that feed solely on conifer trees and follow complex life cycles in which the diet fluctuates in nutrient levels. Adelgids are unusual in that both senior and junior symbionts appear to have been replaced repeatedly over their evolutionary history. Genomes can provide clues to understanding symbiont replacements, but only the dual symbionts of hemlock adelgids have been examined thus far. Here, we sequence and compare genomes of four additional dual-symbiont pairs in adelgids. We show that these symbionts are nutritional partners originating from diverse bacterial lineages and exhibiting wide variation in general genome characteristics. Although dual symbionts cooperate to produce nutrients, the balance of contributions varies widely across pairs, and total genome contents reflect a range of ages and degrees of degradation. Most symbionts appear to be in transitional states of genome reduction. Our findings support a hypothesis of periodic symbiont turnover driven by fluctuating selection for nutritional provisioning related to gains and losses of complex life cycles in their hosts.