Higher Leaf Damage Research Articles

Damage on grapevine cv. Niagara Rosada leaves caused by the combined effect of temperature and Asian grapevine leaf rust (Neophysopella tropicalis)

AbstractAsian grapevine leaf rust (AGLR), caused by Neophysopella tropicalis, is a problem for viticulture, especially in latitudes lower than 25° S, which include the most significant production regions in Brazil. Climate change has raised new concerns in agriculture as temperature can affect the resistance of plants to pathogens. With the aim of understanding how air temperature rise affects the AGLR pathosystem, measurements of leaf gas exchange and epidemiological and histopathological analyses were carried out on control and inoculated leaves of Vitis labrusca ‘Niagara Rosada’ grown at 25°C and 30°C. The lesion density and rust severity were higher at 25°C than 30°C, and the ratio between adaxial surface necrosis and the abaxial surface area occupied by pustules was >1 only at 30°C, presenting a necrosis not associated to the pathogen lesion. In fact, leaf necrosis was identified on control plants kept at 30°C and associated with gerontoplasts, representing accelerated leaf senescence. The AGLR pathogen reduced gas exchange and photosystem II activities at 25°C, with no difference between control and inoculated plants at 30°C. Our results indicate that AGLR is sensitive to increasing air temperature. However, the accelerated leaf senescence caused by the combination of N. tropicalis infection and temperature on Niagara Rosada can lead to high leaf damage.

Hubungan antara Penyobekan Daun Secara Mekanik terhadap Serangan Penggulung Daun Pisang

<p>Mechanical control as an effort to reduce <em>Erionata thrax</em> attacks needs to develop of them was torning the leaves. The objective of this research was to determine the effect of leaf torning on the intensity of the damage and determine the level of <em>E</em><em>.</em><em> thrax</em> attack damage in various cultivars. This research was conducted in Semarang, Central Java from September-December 2018. This research used a field experiment method with four treatments of tearing distance of 0 cm, 20 cm, 30 cm, and 40 cm in four banana cultivars, namely Mas Kirana, Ambon, Kepok, and Raja Bulu. The result showed that leaf damage was related to torning distance, but not to the cultivars. The value of regression between torning distance and leaf damage was very low. The torning distance of 40 cm had the highest leaf damage, number of larvae populations, and number of leaf rolls. The torning distance of 20 cm reduced the leaf damage, the number of larvae populations and the number of rolls. The lowest leaf damage is in Mas Kirana cultivar and the highest leaf damage is in Raja Bulu cultivars. Raja Bulu cultivar had the highest attack intensity.</p>

Organic Mulch Increases Insect Herbivory by the Flea Beetle Species, Disonycha glabrata, on Amaranthus spp.

Amaranth (Amaranthus spp.) is an increasingly high-valued niche vegetable crop among small organic growers in North Carolina, due to its increasing demand among diverse immigrant groups. Production is however hampered by insect pests such as the flea beetle (FB), Disonycha glabrata (Coleoptera: Chrysomelidae), that cause significant yield reduction. Chemical insecticides are generally applied for pest control despite their known risks to health and the environment. Integrated pest management (IPM), which is a cost effective and environmentally friendly approach is still under-exploited in vegetable production by small growers. We studied IPM approaches, suitable for organic production of amaranth by screening nine amaranth varieties for resistance to the flea beetle (FB), D. glabrata, grown with, and without, mulch. D. glabrata population was 60% higher in plots with mulch compared to plots without. The amaranth varieties Molten fire and Green Callaloo recorded the lowest and the highest beetle population commensurate with low, and high leaf damage, respectively. Conversely, leaf yields in the mulched plots were 50% less than recorded in the zero-mulch counterpart, with Green Callaloo variety recording the lowest. These findings will serve as building blocks for a sustainable pest management plan that is appropriate for organic production of Amaranthus spp. in North Carolina.

Compensation to simulated insect leaf herbivory in wild cotton (Gossypium hirsutum): responses to multiple levels of damage and associated traits.

Identifying the mechanisms of compensation to insect herbivory remains a major challenge in plant biology and evolutionary ecology. Most previous studies have addressed plant compensatory responses to one or two levels of insect herbivory, and the underlying traits mediating such responses remain elusive in many cases. We evaluated responses associated with compensation to multiple intensities of leaf damage (0% control, 10%, 25%, 50%, 75% of leaf area removed) by means of mechanical removal of foliar tissue and application of a caterpillar (Spodoptera exigua) oral secretions in 3-month-old wild cotton plants (Gossypium hirsutum). Four weeks post-treatment, we measured plant growth and multiple traits associated with compensation, namely: changes in above- and belowground, biomass and the concentration of nutrients (nitrogen and phosphorus) and non-structural carbon reserves (starch and soluble sugars) in roots, stems and leaves. We found that wild cotton fully compensated in terms of growth and biomass allocation when leaf damage was low (10%), whereas moderate (25%) to high leaf damage in some cases led to under-compensation. Nonetheless, high levels of leaf removal (50% and 75%) in most cases did not cause further reductions in height and allocation to leaf and stem biomass relative to low and moderate damage. There were significant positive effects of leaf damage on P concentration in leaves and stems, but not roots, as well as a negative effect on soluble sugars in roots. These results indicate that wild cotton fully compensated for a low level of leaf damage but under-compensated under moderate to high leaf damage, but can nonetheless sustain growth despite increasing losses to herbivory. Such responses were possibly mediated by a re-allocation of carbohydrate reserves from roots to shoots.

Seasonal assembly of arthropod communities on milkweeds experiencing simulated herbivory

The seasonal assembly of arthropod communities is shaped by biotic and abiotic aspects of the habitat that limit the appearance or activity phenology of potential community members. In addition, previous interactions within the community, such as herbivore-induced plant defensive responses, aggregation, and predator avoidance likely affect the assembly of arthropod communities on individual plants. We observed the phenology of arthropod communities and defensive plant traits on 100 milkweed (Asclepias eriocarpa) individuals at monthly intervals over a growing season. We experimentally wounded a subset of plants each month (April–August) to observe the effect of simulated added herbivore damage on the seasonal assembly of these arthropod communities. All plant traits and measures of arthropod communities changed over the season. The observed response to experimental leaf damage suggested a trend of induced susceptibility in early months, but not late months. Plants receiving early-season simulated herbivory experienced more subsequent leaf damage than unmanipulated plants. We observed several lagged correlations in our study indicating that blue milkweed beetle (Chrysochus cobaltinus) abundance was lower in months following high natural leaf damage, and that the abundance of a secondary omnivore (Lygaeus kalmii) and total predator abundance tended to follow months with high C. cobaltinus abundance. Ahistorical habitat factors determined much of the observed seasonality of arthropod communities, but induced responses to simulated herbivory also contributed historical effects that influenced arthropod community assembly.

Arabidopsis response to the spider mite Tetranychus urticae depends on the regulation of reactive oxygen species homeostasis

Reactive oxygen species (ROS) are molecules that play a prominent role in plant response to numerous stresses, including plant interactions with herbivores. Previous findings indicate that Arabidopsis plants showed an increase in H2O2 accumulation after Tetranychus urticae infestation. Despite its importance, no information has been reported on the relationships between ROS-metabolizing systems and the spider mite-triggered plant-induced responses. In this work, four ROS-related genes that were differentially expressed between the resistant Bla-2 and the susceptible Kon Arabidopsis accessions were selected for the analysis. These genes encode proteins putatively involved in the generation (BBE22) and degradation (GPX7 and GSTU4) of H2O2, and in the degradation of ascorbate (AO). Overexpressing BBE22 and silencing GPX7, GSTU4 and AO resulted in higher leaf damage and better mite performance relative to the wild-type plants. Minor effects on H2O2 accumulation obscure major effects on the expression of genes related to ROS-metabolism and JA and SA signaling pathways, and on ROS-related enzymatic activities. In conclusion, the integration of ROS and ROS-related compounds and enzymes in the response of Arabidopsis to the spider mite T. urticae was confirmed. However, the complex network involved in ROS signaling makes difficult to predict the impact of a specific genetic manipulation.

Herbivory causes increases in leaf spinescence and fluctuating asymmetry as a mechanism of delayed induced resistance in a tropical savanna tree

Background and aims – Leaf spinescence is thought to be a defense against herbivory and may increase in years following high herbivory pressure (DIR – delayed induced resistance). Besides DIR, herbivory also causes plant stress, which can be assessed using fluctuating asymmetry analysis (FA – random departures from leaf bilateral symmetry). In this two-year field study we first investigated the relationships between herbivory, FA and spinescence in Solanum lycocarpum trees during an outbreak of moth caterpillars in 2010; then in 2011 we examined whether plants with intense herbivory the previous year presented changes in FA (herbivory induced stress) and spinescence. Key results – In 2010, leaves damaged by moths were significantly more asymmetrical than undamaged leaves. In addition, moths preferentially fed on leaves with fewer and shorter spines. In 2011, plants severely attacked by moths the year before showed significant increases in FA (28%), spine abundance (21%) and spine length (84%), compared to less damaged plants. Conclusions – Our data suggest a delayed response of S. lycocarpum to herbivory, in that plants subjected to high leaf damage the previous year maximized their display of anti-herbivore mechanisms, in this case, leaf spinescence. This is one of the few studies to show that FA increased as a response to herbivore attack. We conclude that FA can be used as an indicator of plant stress following leaf damage.

Effects of different cultivation systems in leaf traits and herbivory damage in Ilex paraguariensis (Aquifoliaceae)

Different environmental conditions are crucial to determine many attributes in plants by selective pressures. Plant traits and ecological interactions may present variation in outputs in these distinctive selection scenarios. In south Brazil, yerba mate (Ilex paraguariensis A. St.-Hil.) has been cultivated in monoculture and in consortium systems, differing significantly in lightning intensity and associated plant richness. In this study, three areas of both cultivation systems were monitored to verify the plant outputs in leaf area and herbivory damage. Our results showed that consortium system cultivation presents higher values of leaf area and higher damage by herbivory. Higher leaf area in consortium system corresponds to numerous studies and corroborates the phenotypic plasticity expected for Ilex paraguariensis. On the other hand, the higher leaf damage opposed the hypothesis that greater plant richness should promote the best herbivory control by natural enemies. Despite the higher foliar loss plants cultivated under consortium system present adequate leaf area to farmers. Beside species richness, other plant community traits play important role in mitigation of herbivory.

Field screening of different genotypes of chilli against infestation of thrips

In order to explore the possibility of sources of resistance and relative tolerance of the cultivars a total of 69 germplasm consisting of diverse phenotypic and genetic makeup were evaluated against thrips damages on the basis of symptoms occurring on the leaves during two consecutive seasons under open field conditions at the Indian Institute of Vegetable Research, Varanasi. The tolerance index was calculated by taking into consideration the injury grade (IG) showed that none of the genotype were found free from the infestation. The average of two years data showed that the genotype LCA 436 (4.51 LCI) had highest leaf damage followed by 9852-173 PT-3 (4.37 LCI) while lowest leaf curl (0.43 LCI) was found in the genotype Taiwan-2 followed by PDG-1 A (0.60 LCI) and DC-28 (0.79 LCI). The genotypes based on leaf curl index, grouped in to different categories showed that none of the screened genotypes were found resistant. Only three genotypes i.e. PDG-1 A, Taiwan-2, DC-28 were found moderately resistant. The slightly resistant category (1.01–2.0 LCI) included 10 genotypes. Twenty two genotypes were found moderately susceptible and twenty six as susceptible. Six genotypes JCA-9, KADDI, AC-ASSAM-9-UP, 9852-173 PT-3, LCA 436, BS-80 with 4.01–5.0 leaf curl index were categorized as highly susceptible genotypes.

Insect Herbivores and Leaf Damage along Successional and Vertical Gradients in a Tropical Dry Forest

AbstractThe availability and quality of resources for herbivores in tropical dry forests (TDFs) vary in time and space, affecting herbivore guilds differently across spatial scales (both horizontally and vertically), with consequences to the distribution of leaf damage in these forests. We attempted to elucidate the distribution patterns of herbivorous insect guilds and leaf damage throughout the secondary succession and vertical stratification along the rainy season in a Brazilian TDF. With the advance of the succession, a greater richness and abundance of herbivorous insects were found, resulting in higher leaf damage in intermediate and late stages. This pattern, however, was not observed for the frequency of leaf miners. At a smaller spatial scale, the host tree height positively affected the richness and abundance of insects. The higher leaf damage was found in canopy, which also harbored a greater richness and abundance of chewing herbivores compared to the understory at both the beginning and the end of the rainy season. Although for sap‐sucking insects, this was only true at the beginning of the season. We detected a decrease in insect richness and abundance at the end of the rainy season, probably due to a synchronization of insect activity with the availability of young, highly nutritious plant tissues. These results are consistent with other studies that found a general trend of increasing richness and abundance of herbivorous insects and leaf damage throughout the secondary succession (early to late stages) and between vertical strata (understory to canopy), suggesting that forest complexity positively affects herbivores.

Increased drought stress resilience of maize through endophytic colonization by Burkholderia phytofirmans PsJN and Enterobacter sp. FD17

Drought is one of the major environmental stresses that adversely affects crop growth and productivity worldwide. The effect of inoculation of two bacterial endophytes Burkholderia phytofirmans strain PsJN and Enterobacter sp. FD17 on growth, water status and photosynthetic activity of two maize cultivars under drought stress conditions was investigated. Plants were exposed to drought stress by withholding irrigation at vegetative growth stage (45 days after planting). The inoculant strains efficiently colonized maize seedlings and were recovered from root, shoot and leaves of both irrigated and stressed plants. Drought stress had drastic effects on growth, leaf water content and photosynthesis of maize seedlings. Our results revealed that bacterial inoculation minimized the drought stress-imposed effects significantly increasing shoot biomass, root biomass, leaf area, chlorophyll content, photosynthesis, and photochemical efficiency of PSII. Similarly, bacterized seedlings showed higher leaf relative water content (30%) compared to control, whereas 43% higher leaf damage in terms of relative membrane permeability was observed in non-inoculated plants under drought stress. Strain PsJN was more efficient than FD17 in terms of influencing growth and physiological status of the seedlings under drought stress. Our data suggest that maize plants can be protected from inhibitory effects of the drought stress by the harbored bacterial endophytes, although the degree of protection depends on the type of the bacterial strain and the plant genotype.

Omnipresence of leaf herbivory by invertebrates and leaf infection by fungal pathogens in agriculturally used grasslands of the Swiss Alps, but low plant damage

Agriculturally used grasslands in the Alps are characterised by a trade-off between high fodder production in some and high plant species richness in others. In contrast to plant species richness and production, however, little is known on the relevance of biological interactions between plants, invertebrate herbivores, and fungal pathogens for grasslands in the Alps. At the time when the vegetation was fully developed, but prior to agricultural use, we examined whether leaf damage by herbivory and fungal pathogen infection, and their diversity, are affected by plant functional group, land use, and altitude. Moreover, we studied whether extent and diversity of leaf damage are related to each other, to plant species richness, and to standing crop. We recorded the leaf area damaged by ten types of herbivory and five types of fungal pathogen infection on 12,054 plant leaves of legumes, other forbs, and graminoids collected in 215 grassland parcels in 12 valleys in the Swiss Alps. With 83 % of all leaves infested, herbivory and fungal pathogen infection were omnipresent. However, only 2.7 % leaf area was damaged by herbivory and 1.2 % by fungal pathogens. Damage by herbivory was highest on legumes, and damage by fungal pathogens was highest on graminoids. More leaf damage by herbivory occurred in traditionally mown sites and at lower altitudes, while damage by fungal pathogen infection was independent of land use and altitude. Most types of herbivory were found on legumes and on leaves from fertilised sites, whereas the number of fungal pathogen types was highest on graminoids and in unfertilised sites. Larger standing crop was associated with higher leaf damage and diversity of herbivory types per leaf. Neither damage by herbivory nor by fungal pathogens was correlated with plant species diversity. In more plant species rich parcels, the number of herbivory types was lower at the leaf level, but tended to be higher at the parcel level. Our results highlight the omnipresence of plant–herbivore and plant–pathogen interactions. They suggest that current land use changes from mowing to grazing or to abandonment decrease the diversity of herbivory, and that fertilisation decreases pathogen diversity. As our results did not reveal conservation conflicts between diversities of plants, herbivores, and fungal pathogens, and as the damage from herbivory and pathogens is generally low, we conclude that for protecting the high diversity of plant–herbivore and plant–pathogen interactions a diverse low-intensity land use should be maintained.

Host Plant Utilization Within Family Ericaceae by the Andromeda Lace Bug Stephanitis takeyai (Hemiptera: Tingidae)

This study examined host plant utilization by the Andromeda lace bug, Stephanitis takeyai Drake and Maa, within the family Ericaceae. The preferred host of S. takeyai is the Japanese pieris, Pieris japonica (Thunb.) D. Don ex G. Don, but it has been reported to exhibit host alternation and also to occur on other unrelated host plants. We examined the acceptability of ten landscape and fruit plants belonging to the family Ericaceae (Rhododendron calendulaceum, Rhododendron ‘Hampton Beauty’, Rhododendron ‘Autumn Empress’, Vaccinium arboreum, Vaccinium virgatum, Calluna vulgaris, Kalmia latifolia, Pieris floribunda, Pieris phillyreifolia and Pieris japonica ‘Temple Bells’) to S. takeyai. In no-choice tests adult survival did not vary significantly among the taxa. Highest leaf damage was recorded on P. japonica and R. calendulaceum, while slight damage was noted on V. arboreum and Rhododendron ‘Hampton Beauty’. Nymph emergence was observed in P. japonica, R. calendulaceum and Rhododendron ‘Hampton Beauty’. In multi-choice tests adult presence on leaves did not vary significantly except on day 9, when adults were more numerous on ‘Temple Bells’. Maximum leaf damage was recorded on P. japonica, ‘Temple Bells’. Several plants like Rhododendron and Vaccinium spp., which may not be favorable hosts, could serve as reservoirs for the pest.

Biotic resistance to Chrysanthemoides monilifera ssp. monilifera in Tasmania

AbstractBoneseed, Chrysanthemoides monilifera ssp. monilifera (Asteraceae) is concentrated in and near cities and towns on the north and east coasts of Tasmania. Its absence from intervening rural and bushland areas cannot be attributed to environmental conditions or a lack of time for dispersal from introduction points. The hypothesis tested in the present paper is that the range of boneseed in Tasmania is limited by biotic resistance through herbivory. Cafeteria experiments and field observations showed that sheep (Ovis aries), cattle (Bos taurus), Tasmanian pademelons (Thylogale billardierii), Bennett's wallabies (Macropus rufogriseus), garden weevils (Phlyctinus callosus) and native invertebrates all consumed boneseed, while common brushtail possums (Trichosurus vulpecula) did not. A boneseed population subjected to sheep grazing for 168 days suffered high mortality, while an adjacent ungrazed population survived intact. A replicated exclosure experiment showed that 75 days of grazing by cattle reduced the size of boneseed plants. Observations of a population subject to Bennett's wallaby and Tasmanian pademelon grazing over 1 year and 2 months showed consistently high leaf damage to foliage within pademelon reach and a decline in population, with high mortality rates in the driest and coldest times. Leaf loss attributable to invertebrates did not prevent a nearby population without wallabies from growing. The distributions of the taxa were consistent with biotic resistance, with those demonstrating no severe effect on boneseed individuals widespread, while those with evidence of severe effects more common in rural areas than in urban areas. Boneseed seemed unlikely to survive for very long at normal stocking levels. Macropod grazing, particularly that of T. billardierii, may also inhibit the invasion of boneseed. Thus, the recent introduction of foxes to Tasmania may not only cause the extinction of species such as T. billardierii, but also may cause an expansion of the range of boneseed.

Seasonal impact on physiological leaf damage risk of Aechmea hybrid under greenhouse conditions

For decades bromeliad growers have to face severe leaf damage problems occurring as necrotic spots on leaves of sensitive CAM plants such as Aechmea, both in cultivation and transport. These physiological problems mainly arise during the summer period from June to September. Previous research made clear that high malic acid concentrations in the early morning generate the driving force for cellular osmotic uptake of water and can consequently induce lethal turgor pressures in sensitive Aechmea cultivars. Although it is commonly known that CAM and its related metabolites can be influenced by different environmental factors, this relationship is poorly investigated under commercial greenhouse conditions. Therefore the authors carried out four seasonal diurnal experiments with a high leaf damage sensitive Aechmea cultivar spread equally over a 1-year period. Malic acid dynamics revealed that during the critical summer period plants fail to induce malic acid consumption in the early morning causing prolonged high levels of malic acid in the leaves. Moreover, relative water content measurements did confirm that enough water is always available inside the leaves and that even slight changes in water status can be disastrous for the leaves. During the rest of the year malic acid is consumed early in the morning and is not long enough available in the leaf to cause lethal water flow. The comprehension of why this damage induction mechanism is closely related with the summer period is essential to search for possible solutions to prevent the appearance of this physiological leaf damage problem in the future.

Severity of damage to Trifolium repens leaves by certain invertebrate species in mixed perennial ryegrass/white clover swards: response to cultivar, cutting frequency and sward characteristics

The severity of damage by certain invertebrate species to white clover (Trifolium repens) leaves on the main stolons of plants grown in mixed perennial ryegrass/white clover swards was examined in a field experiment in the Netherlands in which two cutting frequencies (high and low) and three white clover cultivars (Retor, Alice and Gwenda) were used. The damage to the leaves was described in terms of the numbers of damaged leaves and the extent of that damage (slight <20%, moderate 20–50% and heavy >50%). The relationships between leaf damage and sward characteristics (white clover content, above‐ground biomass and sward height) were evaluated throughout the growing season.Over the whole experimental period, 23·7% and 27·4% of the total number of leaves produced per stolon were damaged by slugs and weevils in the low‐ and high‐frequency cutting treatments respectively. High‐frequency cutting increased the number of leaves in the total leaf damage and moderate leaf damage categories by 21·4% and 34·8%, respectively, compared with the low‐frequency cutting. The cv. Retor (medium‐leaved) experienced the most severe damage by invertebrates. It had much higher leaf damage than cvs Alice (large‐leaved) and Gwenda (small‐leaved) at either cutting frequency, both in the total number of damaged leaves and in the different damage categories. Differences among cultivars in the number of damaged leaves and relative leaf damage occurred primarily in spring, late summer and autumn, but did not differ during the early‐ and mid‐summer months.This study indicates that variations in leaf damage among clover cultivars were associated with differences in measured sward characteristics. Both the number of damaged leaves and the relative leaf damage were strongly negatively correlated with white clover content and biomass in spring, late summer and autumn under each cutting treatment. White clover content and biomass explained 65%, 59% and 50% of the variation in the number of damaged leaves in spring, late summer and autumn, respectively, and 58%, 57% and 45% of the variation in relative leaf damage in these three periods. Thus, sward characteristics may play a role in regulating the severity of invertebrate damage to clover leaves in addition to the primary effects of HCN.

Abundance and stratification of foliage arthropods in a lowland rain forest of Cameroon

Abstract.Arthropod densities and apparent leaf damage were compared within the canopy ecotone and the shrub layer of a lowland rain forest in Cameroon, using a branch clipping method.Most of the individuals collected consisted of ants (average 44%) and various herbivores (31%). Overall arthropod densities amounted to 17 individuals per sample, which, on average, consisted of 0.85 m2of foliage area. Arthropod densities were lower than on temperate foliage.Arthropod densities were about 3 times higher in the canopy than within the shrub layer. In particular, ants and herbivores were significantly more abundant in the canopy than within the shrub layer. Usually, layer effects rather than site effects appeared to cause greater variance in arthropod abundance.Arthropod species‐richness, as estimated by the number of operational taxonomic units sorted, was higher in canopy samples than in samples obtained from the shrub layer. However, apparent leaf damage was higher within the shrub layer (10.9%) than on the canopy (5.2%).Possible factors responsible for the high densities of ants and herbivores on the canopy and for the high leaf damage within the shrub layer are discussed.

Incidence Pattern of Rice Caseworm (<i>Nymphula</i> sp.)

Incidence pattern of rice caseworm were studied from T. Aman (July - December) 1995 to Boro (December - May) 1998 at BRRI farm, Gazipur. Rice caseworm mostly damaged the rice plants 2 to 4 weeks after transplanting. The incidence occurred at 15th August and subsequent transplanting dates during T. Aman season and the highest leaf damage was observed in case of mid October planting. In Boro season, the incidence occurred in the late February. There were two peak incidence of caseworm in the month of August and October. 
 
 Key words: Caseworm, Nymphula sp., incidence, leaf damage.