We collected data on mortality of late-instar gypsy moth, Lymantria dispar (L.), from outbreak populations over 4 wk in June 2017 at 10 sites in the New England region of the United States, along with estimated rainfall at these sites. Deposition of airborne conidia of the fungal pathogen, Entomophaga maimaiga Humber, Shimazu & R.S. Soper, was measured at these same sites as well as at seven other locations in New England. We also quantified the geographical distribution of gypsy moth-caused defoliation in New England in 2017 and 2018 from Landsat imagery. Weekly mortality of gypsy moth larvae caused by E. maimaiga correlated with local deposition of conidia from the previous week, but not with rainfall. Mortality from this pathogen reached a peak during the last 2 wk of gypsy moth larval development and always exceeded that caused by LdNPV, the viral pathogen of gypsy moth that has long been associated with gypsy moth outbreaks, especially prior to 1989. Cotesia melanoscela (Ratzeburg) was by far the most abundant parasitoid recovered and caused an average of 12.6% cumulative parasitism, but varied widely among sites. Deposition of E. maimaiga conidia was highly correlated with percent land area defoliated by gypsy moths within distances of 1 and 2 km but was not significantly correlated with defoliation at distances greater than 2 km. This is the first study to relate deposition of airborne conidia of E. maimaiga to mortality of gypsy moths from that agent.
- MeSH
- Entomophthorales * MeSH
- Larva MeSH
- Moths * MeSH
- Spores, Fungal MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The mechanisms linking C/N balance to N uptake and assimilation are central to plant responses to changing soil nutrient levels. Defoliation and subsequent regrowth of grasses both impact C partitioning, thereby creating a significant point of interaction with soil N availability. Using defoliation as an experimental treatment, we investigated the dynamic relationships between plant carbohydrate status and NO3--responsive uptake systems, transporter gene expression, and nitrate assimilation in Lolium perenne L. High- and low-affinity NO3- uptake was reduced in an N-dependent manner in response to a rapid and large shift in carbohydrate remobilization triggered by defoliation. This reduction in NO3- uptake was rescued by an exogenous glucose supplement, confirming the carbohydrate dependence of NO3- uptake. The regulation of NO3- uptake in response to the perturbation of the plant C/N ratio was associated with changes in expression of putative high- and low-affinity NO3- transporters. Furthermore, NO3- assimilation appears to be regulated by the C-N status of the plant, implying a mechanism that signals the availability of C metabolites for NO3- uptake and assimilation at the whole-plant level. We also show that cytokinins may be involved in the regulation of N acquisition and assimilation in response to the changing plant C/N ratio.
- MeSH
- Nitrates metabolism MeSH
- Nitrogen metabolism MeSH
- Lolium genetics growth & development metabolism MeSH
- Plant Leaves metabolism MeSH
- Carbohydrate Metabolism * MeSH
- Gene Expression Regulation, Plant * MeSH
- Plant Proteins genetics metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Background and Aims: The efficiency of N assimilation in response to defoliation is a critical component of plant regrowth and forage production. The aim of this research was to test the effect of the internal C/N balance on NO3- assimilation and to estimate the associated cytokinin signals following defoliation of perennial ryegrass ( Lolium perenne L. 'Grasslands Nui') plants. Methods: Plants, manipulated to have contrasting internal N content and contrasting availability of water soluble carbohydrates (WSCs), were obtained by exposure to either continuous light or short days (8:16 h light-dark), and watered with modified N-free Hoagland medium containing either high (5 m m ) or low (50 μ m ) NO3- as sole N source. Half of the plants were defoliated and the root, sheath and leaf tissue were harvested at 8, 24 and 168 h after cutting. The spatiotemporal changes in WSCs, synthesis of amino acids and associated cytokinin content were recorded after cutting. Key Results: Leaf regrowth following defoliation involved changes in the low- and high-molecular weight WSCs. The extent of the changes and the partitioning of the WSC following defoliation were dependant on the initial WSC levels and the C and N availability. Cytokinin levels varied in the sheath and root as early as 8 h following defoliation and preceded an overall increase in amino acids at 24 h. Subsequently, negative feedback brought the amino acid response back towards pre-defoliation levels within 168 h after cutting, a response that was under control of the C/N ratio. Conclusions: WSC remobilization in the leaf is coordinated with N availability to the root, potentially via a systemic cytokinin signal, leading to efficient N assimilation in the leaf and the sheath tissues and to early leaf regrowth following defoliation.
Despite the increasing rate of urbanization, the consequences of this process on biotic interactions remain insufficiently studied. Our aims were to identify the general pattern of urbanization impact on background insect herbivory, to explore variations in this impact related to characteristics of both urban areas and insect-plant systems, and to uncover the factors governing urbanization impacts on insect herbivory. We compared the foliar damage inflicted on the most common trees by defoliating, leafmining and gall-forming insects in rural and urban habitats associated with 16 European cities. In two of these cities, we explored quality of birch foliage for herbivorous insects, mortality of leafmining insects due to predators and parasitoids and bird predation on artificial plasticine larvae. On average, the foliage losses to insects were 16.5% lower in urban than in rural habitats. The magnitude of the overall adverse effect of urbanization on herbivory was independent of the latitude of the locality and was similar in all 11 studied tree species, but increased with an increase in the size of the urban area: it was significant in large cities (city population 1-5 million) but not significant in medium-sized and small towns. Quality of birch foliage for herbivorous insects was slightly higher in urban habitats than in rural habitats. At the same time, leafminer mortality due to ants and birds and the bird attack intensity on dummy larvae were higher in large cities than in rural habitats, which at least partially explained the decline in insect herbivory observed in response to urbanization. Our findings underscore the importance of top-down forces in mediating impacts of urbanization on plant-feeding insects: factors favouring predators may override the positive effects of temperature elevation on insects and thus reduce plant damage.
KEY MESSAGE: Two new TDZ derivatives (HETDZ and 3FMTDZ) are very potent inhibitors of CKX and are promising candidates for in vivo studies. Cytokinin hormones regulate a wide range of essential processes in plants. Thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5-yl urea, TDZ), formerly registered as a cotton defoliant, is a well known inhibitor of cytokinin oxidase/dehydrogenase (CKX), an enzyme catalyzing the degradation of cytokinins. TDZ thus increases the lifetime of cytokinins and their effects in plants. We used in silico modeling to design, synthesize and characterize twenty new TDZ derivatives with improved inhibitory properties. Two compounds, namely 1-[1,2,3]thiadiazol-5-yl-3-(3-trifluoromethoxy-phenyl)urea (3FMTDZ) and 1-[2-(2-hydroxyethyl)phenyl]-3-(1,2,3-thiadiazol-5-yl)urea (HETDZ), displayed up to 15-fold lower IC 50 values compared with TDZ for AtCKX2 from Arabidopsis thaliana and ZmCKX1 and ZmCKX4a from Zea mays. Binding modes of 3FMTDZ and HETDZ were analyzed by X-ray crystallography. Crystal structure complexes, solved at 2.0 Å resolution, revealed that HETDZ and 3FMTDZ bound differently in the active site of ZmCKX4a: the thiadiazolyl ring of 3FMTDZ was positioned over the isoalloxazine ring of FAD, whereas that of HETDZ had the opposite orientation, pointing toward the entrance of the active site. The compounds were further tested for cytokinin activity in several cytokinin bioassays. We suggest that the combination of simple synthesis, lowered cytokinin activity, and enhanced inhibitory effects on CKX isoforms, makes 3FMTDZ and HETDZ suitable candidates for in vivo studies.
Geometrid moths occurring in late autumn and early spring in temperate forest habitats are often harmful defoliators of deciduous stands. Their populations can cause locally cyclic outbreaks and thus preventive monitoring actions have been developed, mainly based on pheromone attraction of males. Females are mostly flightless with reduced or lost wings and reduced senses associated with flying. Males are standard flyers with well-developed eyes and must be able to deal with rapidly changing light conditions during their activity. Although such differences indicate sex-biased differences in reactions to light, this has been insufficiently tested. In conditions of an experimental arena and using light-emitting diodes, we tested the different reactions of the sexes for nine species to precisely defined short segments of the electromagnetic spectrum in the range 360-660 nm. Across all species, males preferred shorter wavelengths up to 500 nm, while females were nonselective and generally less active. The sexes differed by eye size and body mass, with males having significantly larger eyes and lower body mass. Between brachypterous and apterous females, the former had larger eye size, while body mass differences were statistically insignificant. There were differences between the sexes in move-to-light reactions and changes in eye size and body mass in line with wing reduction. While males preferred a relatively distinct range of shorter wavelengths, a method of attraction to lights with distinct narrow spectra could be used markedly to enhance the established methods of forest pest monitoring, either alone or in combination with chemical male attraction.
- MeSH
- Behavior, Animal radiation effects MeSH
- Flight, Animal MeSH
- Linear Models MeSH
- Moths anatomy & histology physiology radiation effects MeSH
- Eye anatomy & histology MeSH
- Sex Characteristics MeSH
- Light * MeSH
- Organ Size MeSH
- Body Size MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Female MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
Levels of polychlorinated dioxins/furans (PCDD/PCDF) in selected environmental samples (soils, sediments, fish, and farm animals) were analyzed from the area of Phong My commune (Thua Thien-Hue province, Vietnam). This area was affected by Agent Orange spraying during the Vietnam war (1968-1971). Whereas PCDD/PCDF content in soil and sediment samples is relatively low and ranges between 0.05 and 5.1 pg WHO-TEQ/g for soils and between 0.7 and 6.4 pg WHO-TEQ/g for sediments, the PCDD/PCDF content in poultry muscle and liver in most cases exceeded the maximum permissible limit of dioxin content per unit fat mass. In some cases of soil and sediments samples, 2,3,7,8-TCDD represented more than 90% of the total PCDD/PCDF, which indicates Agent Orange as the main source.
- MeSH
- Defoliants, Chemical analysis metabolism MeSH
- Dioxins analysis metabolism MeSH
- Livestock metabolism MeSH
- Furans analysis metabolism MeSH
- 2,4-Dichlorophenoxyacetic Acid analysis metabolism MeSH
- 2,4,5-Trichlorophenoxyacetic Acid analysis metabolism MeSH
- Environmental Pollutants analysis metabolism MeSH
- Humans MeSH
- Environmental Monitoring * MeSH
- Gas Chromatography-Mass Spectrometry MeSH
- Polychlorinated Dibenzodioxins analysis metabolism MeSH
- Fishes metabolism MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Vietnam MeSH
BACKGROUND: Current plant--herbivore interaction models and experiments with mammalian herbivores grazing plant monocultures show the superiority of a maximizing forage quality strategy (MFQ) over a maximizing intake strategy (MI). However, there is a lack of evidence whether grazers comply with the model predictions under field conditions. METHODOLOGY/FINDINGS: We assessed diet selection of sheep (Ovis aries) using plant functional traits in productive mesic vs. low-productivity dry species-rich grasslands dominated by resource-exploitative vs. resource-conservative species respectively. Each grassland type was studied in two replicates for two years. We investigated the first grazing cycle in a set of 288 plots with a diameter of 30 cm, i.e. the size of sheep feeding station. In mesic grasslands, high plot defoliation was associated with community weighted means of leaf traits referring to high forage quality, i.e. low leaf dry matter content (LDMC) and high specific leaf area (SLA), with a high proportion of legumes and the most with high community weighted mean of forage indicator value. In contrast in dry grasslands, high community weighted mean of canopy height, an estimate of forage quantity, was the best predictor of plot defoliation. Similar differences in selection on forage quality vs. quantity were detected within plots. Sheep selected plants with higher forage indicator values than the plot specific community weighted mean of forage indicator value in mesic grasslands whereas taller plants were selected in dry grasslands. However, at this scale sheep avoided legumes and plants with higher SLA, preferred plants with higher LDMC while grazing plants with higher forage indicator values in mesic grasslands. CONCLUSIONS: Our findings indicate that MFQ appears superior over MI only in habitats with a predominance of resource-exploitative species. Furthermore, plant functional traits (LDMC, SLA, nitrogen fixer) seem to be helpful correlates of forage quality only at the community level.
- MeSH
- Biomass MeSH
- Herbivory physiology MeSH
- Diet MeSH
- Species Specificity MeSH
- Ecosystem * MeSH
- Quantitative Trait, Heritable * MeSH
- Linear Models MeSH
- Poaceae physiology MeSH
- Sheep physiology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The ozone effect on Norway spruce (Picea abies (L) Karst.) and European beech (Fagus sylvatica L.) was studied on 48 monitoring plots in 2005-2008. These plots represent two major forest tree species stands of different ages in eight regions of the Czech Republic. The forest conditions were represented by defoliation and the annual radial increment of individual trees. The ozone exposure was assessed by using modeled values of mean annual O(3) concentration and the AOT40 index. The malondialdehyde (MDA) content of the foliage was analysed and used as an indicator of oxidative stress. The correlation analysis showed a significant relation of Norway spruce defoliation to the AOT40 exposure index, and European beech defoliation to the MDA level. The radial increment response to ozone was significant only for the European beech: (a) the correlation analysis showed its decrease with increasing AOT40; (b) the regression model showed its decrease with increasing mean annual ozone concentration only at lower altitudes (<700 m a.s.l.).
- MeSH
- Fagus drug effects physiology MeSH
- Air Pollutants analysis toxicity MeSH
- Malondialdehyde metabolism MeSH
- Environmental Monitoring MeSH
- Ozone analysis toxicity MeSH
- Picea drug effects physiology MeSH
- Trees drug effects physiology MeSH
- Air Pollution statistics & numerical data MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Czech Republic MeSH
Triclopyr je systémový herbicid ze skupiny chlorovaných pyridinů. Triclopyr je používán v podobě esteru nebo aminové soli, ke kontrole listnatých dřevin, aniž by ničil trávy a jehličnany, ke kontrole širokolistých plevelů a křoví na různých místech podél cest, na pastvinách a loukách, v lesích a na závodištích, včetně domácích trávníků, přičemž trávy a jehličnany zůstávají nedotčeny. Triclopyr je neobvykle účinný na dřeviny a je používán k likvidaci křovin kolem tratí a odlisťování lesních ploch. Triclopyr není stálý v povrchových vodách. Má omezenou pohyblivost a malou schopnost hromadit se v půdě. Vzhledem k jeho adsorpčním vlastnostem a vzhledem k tomu, že se rozkládá mnoha způsoby, jako jsou fotolýza, metabolizace v rostlinách a mikrobiální degradace, jeho schopnost pronikat do hlubších vrstev půdy a kontaminovat podzemní vody je nízká. Triclopyr se rozkládá v půdě s poločasem mezi 30 a 90 dny. Jedním z produktů jeho degradace je trichlorpyridinol, který může přetrvávat v půdě až jeden rok. V rozkládající se vegetaci je triclopyr aktivní asi 3 měsíce. Látka je mírně toxická pro ptáky. Bylo zjištěno, že je netoxická pro včely a velmi málo toxická pro ryby. Pro člověka má čistý triclopyr velmi nízkou toxicitu při podání ústy. Technický triclopyr je lehce toxický při podání ústy nebo při průniku kůží. Lidé mohou být exponováni rezidui triclopyru v dietě.
Triclopyr is a systemic herbicide, which belongs to the group of chlorinated pyridines. Triclopyr is used in the form of ester or amine salt. It is employed for the control of deciduous woody plants, provided that it does not destroy grass and coniferous woody plants. It is used for the control of broad leafed weeds and bushes at different spots along ways, in pastures and meadows, in forests and sport areas including home lawns, where the grass and coniferous woody plants remain intact after this use. Triclopyr is unusually effective against woody plants and is used for the destruction of bushes along railways and defoliation of forest areas. Triclopyr is not stable in surface waters. It has a limited mobility and low capability of the accumulation in the soil. Given its adsorption characteristics and the fact that it is decomposed in many ways, such as photolysis, metabolic conversion in plants and microbial degradation, its ability to penetrate into deeper soil layers and contaminate ground waters is low. Triclopyr is decomposed in soil with a half-life between 30 and 90 days. One of products of its degradation is trichloropyridinol, which can persist in the soil for as long as one year. In decaying vegetation, triclopyr is active for about 3 months. The substance is slightly toxic to birds. It was found to be non-toxic to bees and slightly toxic to fishes. In humans, pure triclopyr exerts a very low toxicity after its oral administration. Technical triclopyr is slightly toxic after its oral administration or transdermal penetration. Humans can be exposed to triclopyr residua in the food.
- MeSH
- Human Experimentation MeSH
- Animal Experimentation MeSH
- Financing, Organized MeSH
- Glycolates poisoning adverse effects toxicity MeSH
- Herbicides poisoning adverse effects toxicity MeSH
- Skin Diseases etiology MeSH
- Humans MeSH
- Risk MeSH
- Toxicology MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
