A natural fungicide for the control of <Emphasis Type="Italic">Erysiphe betae</Emphasis> and <Emphasis Type="Italic">Erysiphe cichoracearum</Emphasis>

This study examines the effects of a vegetable fungicide on sugar beet powdery mildew (Erysiphe betae) and cucumber powdery mildew (Erysiphe cichoracearum). The formulations consisting of a dispersion of Brassicaceae meal in vegetable or mineral oils on infected leaves of sugar beet, reared in the greenhouse, and of musk melons cultivated under plastic tunnels, were tested in comparison to each oil taken separately. Both formulations containing Brassicaceae meals, caused 94% of conidia to be distorted while for the untreated group only 2% were distorted. Furthermore, the leaf area infected by E. betae was 56% for untreated plants and 2.7 and 9.9% respectively, for plants treated with meal containing mineral and vegetable oil. Vegetable oil considered separately or with Brassicaceae meals showed no phytotoxicity, while the formulations based on mineral oil showed a significantly lower fresh and dry weight on tomato plants. The low level or absence of phytotoxicity of plants treated with vegetable oil formulations suggests that to improve the efficacy of powdery mildew control, they could be used mixed with sulphur. The efficiency of the vegetable formulations in the powdery mildew control observed during these trials encourages further investigation on other parasitic fungi and foliar pathogens.     

Immobilization of the pesticide 2,4‐dichlorophenoxyacetic acid on a silica gel surface

A route for the immobilization of 2,4‐dichlorophenoxyacetic acid (2,4‐D) on silica gel has been developed. In the first step the precursor was prepared by reacting the silylating agent 3‐(trimethoxysilyl)propylamine with silica gel. Nitrogen analysis of this anchored compound showed the presence of 1.16 mmol of amine groups per gram of support. The herbicide was covalently bonded to the amine groups previously anchored onto silica gel. Infrared, [¹³C] and [²⁹Si] NMR spectra supported the reaction between the nitrogen of the amine group of the anchored silica with the carbon on the para‐position of the aromatic ring of 2,4‐D. The reaction yield, 90.3%, was confirmed through elemental analysis. © 2000 Society of Chemical Industry     

Not the one,but the only one: about <Emphasis Type="Italic">Cannabis cryptic virus</Emphasis> in plants showing ‘hemp streak’ disease symptoms

Interveinal chlorosis and leaf margin wrinkling are widespread symptoms of Cannabis sativa. They are traditionally attributed to the so-called hemp streak virus (HSV), but its existence has not been demonstrated yet. To our knowledge, no molecular investigation has so far been performed in order to identify the causal agent of this symptomatology, we therefore decided to use traditional and molecular virology techniques to better characterize symptoms and pursue the etiological agent. No pathogenic virus was found by using targeted PCR reactions and by RNA sequencing, whereas we were able to detect the Cannabis cryptic virus (CanCV) with both techniques. We, therefore, developed an RT-qPCR assay based on a CanCV-specific TaqMan probe and applied it to a wide range of symptomatic and symptomless plants, using a two-step (for quantification), or a one-step (for fast detection) protocol. Both symptoms and the virus were only shown to be transmitted vertically and did not pass via mechanical inoculation or grafting, though we could not find any cause-effect correlation between them. In fact, the virus was found in all the tested hemp samples, and its abundance varied greatly between different accessions and individuals, independently from the presence and severity of symptoms. The suggestion that hemp streak is caused by a virus is therefore questioned. Some abiotic stresses seem to play a role in triggering the symptoms but this aspect needs further investigation. For breeding purposes, a selection of parental plants based on the absence of symptoms proved to be efficient in containment of the disease.     

Determination of total amitraz residue in honey by electron capture capillary gas chroma tography–a simplified method

A gas chromatographic method using a capillary column is described for the determination of total amitraz residue in honey samples. The method consists of a preliminary extraction of the sample, an alkaline hydrolysis, an extraction of the 2, 4-dimethylaniline formed, without the aid of steam distillation/continuous extraction, its derivatisation with heptafluorobutyric anhydride and a gas chromatographic determination using an electron capture detector. The method is very rapid and can be carried out in a test tube. The detection limit is 0.020 mg kg^?1 and recoveries are of the order of 85%.     

Glyphosate-resistant weeds of South American cropping systems: an overview

Herbicide resistance is an evolutionary event resulting from intense herbicide selection over genetically diverse weed populations. In South America, orchard, cereal and legume cropping systems show a strong dependence on glyphosate to control weeds. The goal of this report is to review the current knowledge on cases of evolved glyphosate-resistant weeds in South American agriculture. The first reports of glyphosate resistance include populations of highly diverse taxa (Lolium multiflorum Lam., Conyza bonariensis L., C. canadensis L.). In all instances, resistance evolution followed intense glyphosate use in fruit fields of Chile and Brazil. In fruit orchards from Colombia, Parthenium hysterophorus L. has shown the ability to withstand high glyphosate rates. The recent appearance of glyphosate-resistant Sorghum halepense L. and Euphorbia heterophylla L. in glyphosate-resistant soybean fields of Argentina and Brazil, respectively, is of major concern. The evolution of glyphosate resistance has clearly taken place in those agroecosystems where glyphosate exerts a strong and continuous selection pressure on weeds. The massive adoption of no-till practices together with the utilization of glyphosate-resistant soybean crops are factors encouraging increase in glyphosate use. This phenomenon has been more evident in Argentina and Brazil. The exclusive reliance on glyphosate as the main tool for weed management results in agroecosystems biologically more prone to glyphosate resistance evolution.     

Diverse landscapes have a higher abundance and species richness of spring wild bees by providing complementary floral resources over bees’ foraging periods

Context

Anthropogenic landscape simplification and natural habitat loss can negatively affect wild bees. Alternatively, anthropogenic land-use change may diversify landscapes, creating complementary habitats that maintain overall resource continuity and diversity.

Objectives

We examined the effects of landscape composition, including land-cover diversity and percent semi-natural habitat, on wild bee abundance and species richness within apples, a pollinator-dependent crop. We also explored whether different habitats within diverse landscapes can provide complementary floral resources for bees across space and time.

Methods

We sampled bees during apple bloom over 2 years within 35 orchards varying in surrounding landscape diversity and percent woodland (the dominant semi-natural habitat) at 1 km radii. To assess habitat complementarity in resource diversity and temporal continuity, we sampled flowers and bees within four unique habitats, including orchards, woodlands, semi-natural grasslands, and annual croplands, over three periods from April–June.

Results

Surrounding landscape diversity positively affected both wild bee abundance and richness within orchards during bloom. Habitats in diverse landscapes had different flower communities with varying phenologies; flowers were most abundant within orchards and woodlands in mid-spring, but then declined over time, while flowers within grasslands marginally increased throughout spring. Furthermore, bee communities were significantly different between the closed-canopy habitats, orchards and woodlands, and the open habitats, grasslands and annual croplands.

Conclusions

Our results suggest that diverse landscapes, such as ones with both open (grassland) and closed (woodland) semi-natural habitats, support spring wild bees by providing flowers throughout the entire foraging period and diverse niches to meet different species’ requirements.

     

Agriculturally intensified landscapes are associated with reduced body condition of lady beetles

Landscape Ecology - Agricultural intensification is contributing to a global species decline. Underlying mechanisms include toxic effects of pesticides on non-target organisms and reductions in...     

Immunohistochemical detection of growth hormone (GH) in canine hepatoid gland tumors

The aim of this study was to detect immunohistochemically means growth hormone (GH) in 24 hepatoid gland adenomas and 5 hepatoid gland carcinomas and to compare the difference of immunoreactivity between types of tumors. The tumors were classified according to the WHO standards. Tissue sections which were prepared from formalin-fixed, paraffin wax-embedded tissues from 25 male and 4 female dogs were carried out immunostaining using polyclonal primary anti-hGH and EnVision method. Of 24 hepatoid gland adenomas (perianal gland adenomas) 23 (95.8%) were positive. All 5 hepatoid gland carcinomas (perianal gland carcinomas) were positive. No statistically significant differences in percentage of labelled cells between malignant and benign tumors were seen. The present demonstration of GH in hepatoid gland tumors adds new data on GH in extra-pituitary tissues and hormon-dependent tumors.     

Molecular sequence data of Thecaphora frezii affecting peanut crops in Argentina

In Argentina, Thecaphora frezii is the causal agent of peanut smut, causing severe yield losses in peanut growing areas. In this work sequence data of the large ribosomal subunit (28S rDNA) of four T. frezii specimens from different production regions are provided. A fragment of about 650 bp was amplified by PCR from each of the isolates analyzed. The analysis of the sequences demonstrated 100 % identity among the four specimens and 92–96.3 % identity with sequences of other species of Thecaphora. This is the first study on molecular sequences of this pathogen.     

CropSyst, a cropping systems simulation model

CropSyst is a multi-year, multi-crop, daily time step cropping systems simulation model developed to serve as an analytical tool to study the effect of climate, soils, and management on cropping systems productivity and the environment. CropSyst simulates the soil water and nitrogen budgets, crop growth and development, crop yield, residue production and decomposition, soil erosion by water, and salinity. The development of CropSyst started in the early 1990s, evolving to a suite of programs including a cropping systems simulator (CropSyst), a weather generator (ClimGen), GIS-CropSyst cooperator program (ArcCS), a watershed model (CropSyst Watershed), and several miscellaneous utility programs. CropSyst and associated programs can be downloaded free of charge over the Internet. One key feature of CropSyst is the implementation of a generic crop simulator that enables the simulation of both yearly and multi-year crops and crop rotations via a single set of parameters. Simulations can last a fraction of a year to hundreds of years. The model has been evaluated in many world locations by comparing model estimates to data collected in field experiments. CropSyst has been applied to perform risk and economic analyses of scenarios involving different cropping systems, management options, and soil and climatic conditions. An extensive list of references related to model development, evaluation, and application is provided.