Host Plant Conditions Research Articles

Evolution of Polymorphs in Rhopalosiphum maidis (Hemiptera: Aphididae) in Response to Different Seasonal and Host Plant Conditions

Evolution of Polymorphs in Rhopalosiphum maidis (Hemiptera: Aphididae) in Response to Different Seasonal and Host Plant Conditions

Genome-Wide Analysis of Odorant-Binding Proteins and Chemosensory Proteins in the Bean bug Riptortus pedestris.

Insects have sensitive olfactory systems to interact with environment and respond to the change in host plant conditions. Key genes in the system can be potential targets for developing new and efficient pest behaviour control methods. Riptortus pedestris is an important soybean pest in East Asia and has caused serious damage to the soybean plants in Huang-Huai-Hai region of China. However, the current treatment of pests is dominated by chemical insecticides and lacks efficient sustainable prevention and control technologies. In this study, we identified 49 putative odorant-binding proteins (OBPs) (43 were new genes) and 25 chemosensory proteins (CSPs) (17 were new genes) in R. pedestris genome. These OBP and CSP genes are clustered in highly conserved groups from other hemipteran species in phylogenetic trees. Most RpedOBPs displayed antennal-biased expression. Among the 49 RpedOBPs, 33 were significantly highly expressed in the antennae, including three male-biased and nine female-biased. While many RpedCSPs were detected both in the antennae and in non-antennal tissues, only 11 RpedCSPs displayed antennal-biased expression, in which four RpedCSPs were male-biased and five RpedCSPs were female-biased. Some OBP and CSP genes showed sex-biased expression profiles. Our results not only provide a foundation for future exploration of the functions of RpedOBPs and RpedCSPs but also aid in developing environmentally friendly insecticides in the future.

Host plant identity and condition shape phytophagous insect communities on urban maple (Acer spp.) trees

By mitigating the negative effects of urbanization, urban trees contribute significantly to the well-being of urban citizens. However, trees themselves are also exposed to urban stress that can influence tree condition and tree-herbivore interactions. Maple species (Acer spp.) are among the most commonly planted trees in urban areas throughout North America and Europe. Among these species, field, sycamore, and Norway maple are native to Europe, but tolerate environmental stress to varying degrees. Here, we compared the phytophagous insect communities in the canopy of these tree species in the city of Budapest, Hungary. We also examined the stress level [expressed as peroxidase (POD) enzyme activity], and physiological condition (expressed as degree of leaf necrosis and leaf fall) of the maple trees, and their relationship to herbivore abundance. We observed higher total abundance of phytophagous insects on field and sycamore maple compared to Norway maple. Most herbivorous species were associated with field maple, sycamore had the highest aphid densities, and Norway maple harbored the least specific phytophagous insect community. Field maple trees were in the best condition while Norway maple trees in the worst condition, i.e., with the highest proportion of necrotic leaf surface area. The super-abundant planthopper species, Metcalfa pruinosa positively affected the POD activity of trees, but did not influence their condition. On the contrary, M. pruinosa abundance was driven by tree condition, with higher numbers on healthier trees. Our findings suggest that the abundance of phytophagous insects in the canopy of maple trees is highly determined by tree condition, and in this study field maple had the highest and Norway maple the lowest tolerance for urban stress.

Host plant choice and effect of temperature on feeding behaviour of Perzelia arda (Lepidoptera: Depressariidae), a leaf‐tying larva, on Nothofagaceae from the Andean Patagonian forest

AbstractEnvironmental temperature may cause changes in the physiology and feeding behaviour of herbivorous insects and, consequently, in the damage they can cause. In the Andean Patagonian forest, an eco‐region dominated by trees of the Nothofagaceae family, it is common to find the leaf‐tying larvae Perzelia arda consuming seeds and leaves of several species of Nothofagus genus. The pattern of damage caused by P. arda in these forests varies from year to year and even within seasons. We hypothesise that this phenomenon may be related to an increase in the ambient temperature of this region. The purpose of this work was to determine the host plant preferences of P. arda among four species of Nothofagus genus and to evaluate whether temperature influences the feeding behaviour of the larvae. We first evaluated the food preferences of P. arda by means of two‐choice tests, using leaves of N. alpina, N. obliqua, N. antarctica and N. pumilio as stimuli. Secondly, we evaluated the effect of three levels of temperature on herbivory. Our results demonstrated that P. arda feed on and equally choose the four species of host plants studied. Temperature influenced the feeding behaviour of the larvae; high levels of consumption of N. obliqua occurred at 6°C and differed for the other host plant suggesting that consumption also depends on the type of food resource. In conclusion, the feeding behaviour of P. arda depends on a complex interaction between host plant and abiotic conditions. Further studies are required for a better understanding about the use of resources by this native insect, as well as the ecological consequences.

The seasonal dynamic of Tuta absoluta in Solanum lycopersicon cultivation: Contributions of climate, plant phenology, and insecticide spraying.

A variety of abiotic and biotic factors promoting seasonal variation in the population of insect pests. Knowledge of the timing and magnitude of these factors is important for the study of population dynamics and the development of efficient pest management programs. Currently, there are few studies regarding Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) seasonal dynamics in tomato cultivation under open field conditions, either with or without insecticide application. This study aimed to investigate the effects of tomato phenology, climatic factors, and insecticide spraying on the seasonal dynamics of T. absoluta in tomato cultivation under open field conditions, using data from monitoring performed for 3 years. Insecticide, host plant, and climatic conditions can affect T. absoluta life cycles directly over time, resulting in shifts of peaks of the pest. Insecticides for T. absoluta control reduced injury caused by larvae; however, this was not enough to reduce the density below economic injury levels (EIL) during periods of climatic conditions more suitable for population growth. Tuta absoluta densities surpassed EIL more frequently during the tomato plant fruiting stage. The highest densities of mines and damaged fruits occurred during periods of August to January and September to January in crops without and with the application of insecticides, respectively. Regarding the climatic factors, the highest densities of T. absoluta occurred during periods of increasing air temperature and low rainfall. This study provides relevant insights into the factors that regulate the dynamics of T. absoluta in tomato cultivation and the decision-making process of control of this pest. © 2021 Society of Chemical Industry.

Clonal versus non-clonal milkweeds (Asclepias spp.) respond differently to stem damage, affecting oviposition by monarch butterflies.

BackgroundOviposition decisions are critical to the fitness of herbivorous insects and are often impacted by the availability and condition of host plants. Monarch butterflies (Danaus plexippus) rely on milkweeds (Asclepias spp.) for egg-laying and as food for larvae. Previous work has shown that monarchs prefer to oviposit on recently regrown plant tissues (after removal of above-ground biomass) while larvae grow poorly on plants previously damaged by insects. We hypothesized that these effects may depend on the life-history strategy of plants, as clonal and non-clonal milkweed species differ in resource allocation and defense strategies.Methodology/Principal FindingsWe first confirmed butterfly preference for regrown tissue in a field survey of paired mowed and unmowed plots of the common milkweed A. syriaca. We then experimentally studied the effects of plant damage (comparing undamaged controls to plants clipped and regrown, or damaged by insects) on oviposition choice, larval performance, and leaf quality of two closely related clonal and non-clonal species pairs: (1) A. syriaca and A. tuberosa, and (2) A. verticillata and A. incarnata. Clonal and non-clonal species displayed different responses to plant damage, impacting the proportions of eggs laid on plants. Clonal species had similar mean proportions of eggs on regrown and control plants (≈35–40% each), but fewer on insect-damaged plants (≈20%). Meanwhile non-clonal species had similar oviposition on insect-damaged and control plants (20–30% each) but more eggs on regrown plants (40–60%). Trait analyses showed reduced defenses in regrown plants and we found some evidence, although variable, for negative effects of insect damage on subsequent larval performance.Conclusions/SignificanceOverall, non-clonal species are more susceptible and preferred by monarch butterflies following clipping, while clonal species show tolerance to clipping and induced defense to insect herbivory. These results have implications for monarch conservation strategies that involve milkweed habitat management by mowing. More generally, plant life-history may mediate growth and defense strategies, explaining species-level variation in responses to different types of damage.

Rhizobacterial Community Assembly Patterns Vary Between Crop Species.

Currently our limited understanding of crop rhizosphere community assembly hinders attempts to manipulate it beneficially. Variation in root communities has been attributed to plant host effects, soil type, and plant condition, but it is hard to disentangle the relative importance of soil and host without experimental manipulation. To examine the effects of soil origin and host plant on root associated bacterial communities we experimentally manipulated four crop species in split-plot mesocosms and surveyed variation in bacterial diversity by Illumina amplicon sequencing. Overall, plant species had a greater impact than soil type on community composition. While plant species associated with different Operational Taxonomic Units (OTUs) in different soils, plants tended to recruit bacteria from similar, higher order, taxonomic groups in different soils. However, the effect of soil on root-associated communities varied between crop species: Onion had a relatively invariant bacterial community while other species (maize and pea) had a more variable community structure. Dynamic communities could result from environment specific recruitment, differential bacterial colonization or reflect broader symbiont host range; while invariant community assembly implies tighter evolutionary or ecological interactions between plants and root-associated bacteria. Irrespective of mechanism, it appears both communities and community assembly rules vary between crop species.

Plant Water Stress and Vector Feeding Preference Mediate Transmission Efficiency of a Plant Pathogen.

Pathogen spread by arthropod vectors is the outcome of pathogen-vector-plant interactions, as well as how these interactions are impacted by abiotic and biotic factors. While plant water stress impacts each component of the Pierce's disease pathosystem (Xylella fastidiosa Wells et al., insect vectors, and grapevines), the outcome of interactions in relation to pathogen spread is unknown. The objectives of this study were 1) to determine the role of plant water stress on vector acquisition and inoculation of X. fastidiosa under choice and no-choice conditions for source or recipient vines, and 2) to provide insights into the effects of vineyard irrigation regimes on spread of X. fastidiosa by using a host-vector epidemic model. Under no-choice conditions, pathogen acquisition increased as water stress increased in source plants, while inoculation was not affected by water status of recipient vines. Thus, under no-choice conditions, plant water stress increased transmission of X. fastidiosa. However, when vectors had a choice of an uninfected well-watered versus an infected water-stressed grapevine, transmission efficiency declined as water stress levels increased. While our experimental results produced wide uncertainty estimates, the epidemiological modeling suggested a non-linear relationship between water stress and pathogen spread: moderate water stress enhances pathogen spread but severe or no stress produce equivalent spread. In summary, both host plant condition and vector host preference interacted to determine transmission efficiency of X. fastidiosa.

Coincidental shifts in abundance of nymphalid butterflies: a link with egg deposition behaviour?

In the Greater Manchester area 2017 was an unusual year for nymphalid populations, the first in a thirty year period when the numbers of records of both Vanessa atalanta and Polygonia c-album (single egg-layers) exceeded those of Aglais urticae and A. io (large batch egg-layers). Annual abundances in Greater Manchester of these nettle-feeding nymphalids has revealed that the members of these two groups of species correlate with one another more closely than with either species of the other group. It is suggested that the mode of egg deposition (single egg-layers versus batch-layers) is involved in associations of changes in abundances of the nettle-feeding nymphalids. Other factors in life history may also be involved and are discussed (autumn adult food resources and larval host use). The same pattern is not found in pierids which differ in over-wintering mode and host plant condition. The costs and benefits of different egg-laying strategies are considered in relationship to changing abundances of species.

Transcriptional responses to short-term and long-term host plant experience and parasite load in an oligophagous beetle.

Oligophagous herbivores must adjust their enzymatic machinery to the different host plant species they consume. If different hosts are used from one generation to the next, adaptation may be highly plastic, while if a single host is used over several generations, there may be a longer-term response due to natural selection. Using an experimental evolutionary approach, we investigated effects of long-term experience vs. short-term responses to different host plants in the oligophagous mustard leaf beetle Phaedon cochleariae. After 26 generations of continuous feeding on either Brassica rapa, Nasturtium officinale or Sinapis alba, freshly hatched larvae were kept on these plants or moved to one of the other host plants for ten days. Global transcriptional patterns as shown by microarrays revealed that between 1% and 16.1% of all 25,227 putative genes were differentially expressed in these treatments in comparison with the control line constantly feeding on B. rapa. A shift back from S. alba to B. rapa caused the largest changes in gene transcription and may thus represent the harshest conditions. Infection rates with a gregarine parasite were intermediate in all lines that were constantly kept on one host, but much lower or higher when short-term shifts to other host plants occurred. In conclusion, transcriptional plasticity in genes related to metabolism, digestion and general cellular processes plays a key role in long- and short-term responses of the beetle to changing host plant conditions, whereby the specific conditions also affect the interactions between the beetle host and its gregarine parasite.

Differential accumulation of Xanthomonas campestris pv. campestris proteins during the interaction with the host plant: Contributions of an in vivo system.

Xanthomonas campestris pv. campestris (Xcc) is the causal agent of black rot, a highly destructive disease that affects all brassicas. This work aimed to study the interaction Xcc-Brassica oleracea using an in vivo system in an attempt to identify proteins involved in pathogenicity. We used label-free shotgun 2D-nanoUPLC/MSE to analyze Xcc proteins in three conditions: in the interaction with susceptible (REK) and resistant (REU) plants and in culture medium (control condition). A model of Xcc-susceptible host interaction is proposed and shows that Xcc increases the abundance of several crucial proteins for infection and cell protection. In this study, we also confirmed the differential expression by qPCR analysis of selected genes. This is the first report showing a large-scale identification of proteins in an in vivo host plant condition. Considering that most studies involving phytopathogens are in vitro (growth in culture medium or in plant extract), this work contributes with relevant information related to the plant-pathogen interaction in planta.

Geographic Origin and Host Cultivar Influence on Digestive Physiology ofSpodoptera exigua(Lepidoptera: Noctuidae) Larvae

Digestive enzymatic activity in three geographic strains (Miandiab, Kalposh and Moghan regions) of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) reared on different sugar beet cultivars (Dorothea, Rozier, Persia and Perimer) was studied under laboratory conditions (25 ± 1 °C, 65 ± 5% RH, and a photo period of 16:8 (L:D) h photoperiod). The results of this study demonstrated that digestive protease and amylase activity of S. exigua larvae was affected by both geographic origin of the pest and host plant cultivar. Three strains reared on the same sugar beet cultivars demonstrated different levels of proteolytic and amylolytic activities in fourth and fifth instars. The highest proteolytic and amylolytic activity, in most cases, was observed in larvae collected from Kalposh region. Among different sugar beet cultivars, the highest protease activity in three strains was observed on cultivars Rozier and Perimer. Nevertheless, the highest amylase activity was seen on cultivar Dorothea, and the lowest activity was seen on cultivar Rozier. This study suggested that variations in digestive enzymatic activity of three geographic strains of S. exigua might be attributed to local adaptation with their local host plant and environmental conditions inherent by larvae.

Environmental predictors of shrubby cinquefoil (Dasiphora fruticosa) habitat and quality as host for Maine’s endangered Clayton’s copper butterfly (Lycaena dorcas claytoni)

Population size of habitat-specialized butterflies is limited in part by host plant distribution and abundance. Effective conservation for host-specialist species requires knowledge of host-plant habitat conditions and relationships with the specialist species. Clayton’s copper butterfly (Lycaena dorcas claytoni) is a Maine state-endangered species that relies exclusively on shrubby cinquefoil (Dasiphora fruticosa) as its host. Dasiphora fruticosa occurs in 28 wetlands in Maine, ten of which are occupied by L. d. claytoni. Little is known about environmental conditions that support large, persistent stands of D. fruticosa in Maine. We evaluated the environment (hydrology, pore water and peat nutrients) associated with D. fruticosa distribution, age, and condition in Maine wetlands supporting robust stands of D. fruticosa to compare with L. d. claytoni occurrence. Although dominant water source in D. fruticosa—containing wetlands included both groundwater discharge and surface-flow, D. fruticosa coverage was greater in wetlands with consistent growing season water levels that dropped into or below the root zone by late season, and its distributions within wetlands reflected pore water hydrogen ion and conductivity gradients. Flooding magnitude and duration were greatest during the L.d. claytoni larval feeding period, whereas, mean depth to water table and upwelling increased and were most variable following the L. d. claytoni egg-laying period that precedes D. fruticosa senescence. Oldest sampled shrubs were 37 years, and older shrubs were larger and slower-growing. Encounter rates of L. d. claytoni were greater in wetlands with larger D. fruticosa plants of intermediate age and greater bloom density. Wetland management that combines conditions associated with D. fruticosa abundance (e.g., non-forested, seasonally consistent water levels with high conductivity) and L. d. claytoni occurrence (e.g., drawdown below the root zone following egg-laying, abundant blooms on intermediate-aged D. fruticosa, nearby D. fruticosa-containing wetlands) will aid L. d. claytoni conservation.

Effects of Larval Rearing Temperature and Host Plant Condition on the Development, Survival, and Coloration of African Armyworm, Spodoptera exempta Walker (Lepidoptera: Noctuidae)

Effects of temperature and host plant condition on insect development have been examined in a number of studies but their combined effect is not well investigated. In this study the effects of varying temperatures and host plant conditions and its interaction on development, survival, and coloration of solitarious and gregarious forms of African armyworm (AW), Spodoptera exempta, an outbreak pest species, were studied under laboratory condition. Rearing temperature was found to have significant effects on larval and pupal development and pupal weight in both solitarious and gregarious forms. The effects of host plant condition in both forms were variable; significant effects were consistently observed in pupal development for both gregarious and solitarious forms but not in larval development and pupal weight. Larval and pupal survival of the solitarious form significantly decreased with the decreased in temperature, while only pupal survival decreased with the decreased in temperature in gregarious form. Distinct larval coloration was also observed in different temperatures. Larvae reared at high temperature exhibited lighter coloration, while larvae reared at low temperature exhibited darker coloration regardless of rearing density. The significant interaction of temperature and host plant condition on many aspects of insect fitness measured in this study highlights the need for further studies on the effects of other environmental factors such as relative humidity, rainfall, and light intensity to improve predictions as to how these insect pests will respond to climate change.

Diversity and distribution of rhizobia nodulated with Phaseolus vulgaris in two ecoregions of China

To reveal the diversity and geographic distribution of bean (Phaseolus vulgaris L.) rhizobia in China, a total of 226 strains of nodule bacteria were isolated from bean plants grown in fields of nine sites in northern (ecoregion I) and southern (ecoregion II) regions of China, with soil pH ranged from 8.06 to 4.97. Based upon the phylogenies of housekeeping and symbiotic genes, 96.9% of the isolates were Rhizobium corresponding to four defined species and four unnamed genospecies, while the remaining were five Bradyrhizobium genospecies. Rhizobium leguminosarum, Rhizobium etli and Rhizobium sp. II or IV were dominant in different ecoregions, with varied relative abundances. Therefore, diverse and distinctive bean rhizobial communities exist in different ecoregions of China, demonstrating that the introduction of bean plants has driven the evolution of rhizobia to fit the necessity to nodulate the host plant under the local conditions, mainly the soil pH and the nutrient availability. The predominance of R. etli and the high similarities in the symbiotic genes (nodC and nifH) of all the Rhizobium genospecies with R. etli evidenced that symbiotic genes were transferred from R. etli, possibly introduced to China accompanying the seeds, to the related indigenous rhizobia. These findings enlarged the diversity of bean rhizobia, evidenced the biogeographic patterns of these rhizobia, and demonstrated the possible evolution and emerging of novel rhizobia under the combined selection of host plant and soil conditions.

Alate production in an aphid in relation to ant tending and alarm pheromone

1. Winged dispersal is vital for aphids as predation pressure and host plant conditions fluctuate.2. Ant‐tended aphids also need to disperse, but this may represent a cost for the ants, resulting in an evolutionary conflict of interest over aphid dispersal.3. The combined effects of aphid alarm pheromone, indicating predation risk, and ant attendance on the production of winged aphids were examined in an experiment with Aphis fabae (Homoptera: Aphididae) (Scopoli 1763) aphids and Lasius niger (Formicidae: Formicinae) (Linné, 1758) ants.4. This study is the first to investigate the joint effects of alarm pheromone and ant attendance, and also the first to detect an influence of alarm pheromone on the production of winged morphs in A. fabae.5. After a period of 2 weeks, it was found that aphid colonies exposed to intermittent doses of alarm pheromone produced more winged individuals, whereas ant tending had the opposite effect. The effects were additive on a log scale, and ant attendance had a greater proportional influence than exposure to alarm pheromone. A tentative conclusion is that ants have gained the upper hand in an evolutionary conflict about aphid dispersal.

Mechanisms of species‐sorting: effect of habitat occupancy on aphids' host plant selection

Interspecific interactions such as competition are important factors affecting insect herbivore fitness. Host choice in herbivorous insects including aphids has largely been studied with respect to host plant condition, while the role of competition is also very important. Tansy (Tanacetum vulgare L.) hosts three specialised aphids, Macrosiphoniella tanacetaria (Kaltenbach), Metopeurum fuscoviride Stroyan and Uroleucon tanaceti (L.) (Hemiptera: Aphididae). In this study, a set of greenhouse and field experiments were carried out to investigate whether aphid host plant choice was affected by the presence of the other aphid species. When winged individuals were given the choice between unoccupied plants and plants occupied by the same or another aphid species, choices generally reflected the outcome of competitive interactions among aphids. Colonisation of plants by winged individuals was influenced not only by the presence of other aphids on the host plant but also by previous infestation. The host choice of winged individuals basically reflected competitive hierarchies, i.e. aphids in most cases selected plants where future competition was less likely. By contrast, unwinged aphids did not show any host plant preference. For M. tanacetaria previously infested plants promoted the production of winged offspring. Our results show that competitive interactions could affect host selection behaviour by aphids. In a metacommunity context, such preferences in colonising different habitats leads to species‐sorting through habitat heterogeneity.

Identification and Expression Profiling of Odorant Binding Proteins and Chemosensory Proteins between Two Wingless Morphs and a Winged Morph of the Cotton Aphid Aphis gossypii Glover

Insects interact with their environment and respond to the changes in host plant conditions using semiochemicals. Such ecological interactions are facilitated by the olfactory sensilla and the use of olfactory recognition proteins. The cotton aphid Aphis gossypii can change its phenotype in response to ecological conditions. They reproduce mainly as wingless asexual morphs but develop wings to find mates or new plant hosts under the influence of environmental factors such as temperature, plant nutrition and population density. Two groups of small soluble proteins, odorant binding proteins (OBPs) and chemosensory proteins (CSPs) are believed to be involved in the initial biochemical recognition steps in semiochemical perception. However, the exact molecular roles that these proteins play in insect olfaction remain to be discovered. In this study, we compared the transcriptomes of three asexual developmental stages (wingless spring and summer morphs and winged adults) and characterised 9 OBP and 9 CSP genes. The gene structure analysis showed that the number and length of introns in these genes are much higher and this appears to be unique feature of aphid OBP and CSP genes in general. Another unique feature in aphids is a higher abundance of CSP transcripts than OBP transcripts, suggesting an important role of CSPs in aphid physiology and ecology. We showed that some of the transcripts are overexpressed in the antennae in comparison to the bodies and highly expressed in the winged aphids compared to wingless morphs, suggesting a role in host location. We examined the differential expression of these olfactory genes in ten aphid species and compared the expression profile with the RNA-seq analyses of 25 pea aphid transcriptome libraries hosted on AphidBase.

Dynamics of nonpersistent aphid-borne viruses in lettuce crops covered with UV-absorbing nets

Aphid-transmitted viruses frequently cause severe epidemics in lettuce grown under Mediterranean climates. Spatio-temporal dynamics of aphid-transmitted viruses and its vector were studied on lettuce (Lactuca sativa L.) grown under tunnels covered by two types of nets: a commercial UV-absorbing net (Bionet) and a Standard net. A group of plants infected by Cucumber mosaic virus (CMV, family Bromoviridae, genus Cucumovirus) and Lettuce mosaic virus (LMV, family Potyviridae, genus Potyvirus) was transplanted in each plot. The same virus-infected source plants were artificially infested by the aphid Macrosiphum euphorbiae (Thomas). Secondary spread of insects was weekly monitored and plants were sampled for the detection of viruses every two weeks. In 2008, the infection rate of both CMV and LMV were lower under the Bionet than under the Standard cover, probably due to the lower population density and lower dispersal rate achieved by M. euphorbiae. However, during spring of 2009, significant differences in the rate of infection between the two covers were only found for LMV six weeks after transplant. The spatial distribution of the viruses analysed by SADIE methodology was “at random”, and it was not associated to the spatial pattern of the vector. The results obtained are discussed analyzing the wide range of interactions that occurred among UV-radiation, host plant, viruses, insect vector and environmental conditions. Our results show that UV-absorbing nets can be recommended as a component of an integrated disease management program to reduce secondary spread of lettuce viruses, although not as a control measure on its own.

Role of stressed mango host conditions in attraction of and colonization by the mango bark beetle Hypocryphalus mangiferae Stebbing (Coleoptera: Curculionidae: Scolytinae) and in the symptom development of quick decline of mango trees in Pakistan

AbstractThe mango sudden death syndrome has become a serious threat to the mango industry and caused significant decline in mango production worldwide. The bark beetle Hypocryphalus mangiferae (Stebbing) (Coleoptera: Curculionidae: Scolytinae) has been suggested as a potential vector of the disease based primarily on field observations with little or no supporting empirical data. In this study, we investigated the role of infected mango trees in host attraction and colonization by H. mangiferae to determine if beetle attack and colonization contributes to the disease progression on mango trees. Initially, the role of various stress factors on beetle attraction and disease progression was assessed under lathe house conditions from 2008 to 2009. Results suggest that symptomatic or recently inoculated mango trees (without any obvious symptoms) are preferentially colonized by H. mangiferae. Although not significant, high numbers of beetles attacked stressed or wounded mango trees, compared to healthy or dead mango trees. Disease symptoms after beetle colonization, such as bark splitting, wilting and oozing, were further evaluated. These symptoms showed positive correlation with the degree of disease severity and host plant condition. Furthermore, two fungi, Ceratocystis fimbriata and Lasiodiplodia theobromae, were frequently isolated from the beetle and beetle‐colonized trees. Based on these findings, they suggests that H. mangiferae can vector multiple fungi associated with mango sudden decline disease and play a significant role in outbreaks of this disease.