Advancing cover cropping in temperate integrated weed management

The effects of cover crops on weeds and the underlying mechanisms of competition, physical control and allelopathy are not fully understood. Current knowledge reveals great potential for using cover crops as a preventive method in integrated weed management. Cover crops are able to suppress 70–95% of weeds and volunteer crops in the fall‐to‐spring period between two main crops. In addition, cover crop residues can reduce weed emergence during early development of the following cash crop by presenting a physical barrier and releasing allelopathic compounds into the soil solution. Therefore, cover crops can partly replace the weed suppressive function of stubble‐tillage operations and non‐selective chemical weed control in the fall‐to‐spring season. This review describes methods to quantify the competitive and allelopathic effects of cover crops. Insight obtained through such analysis is useful for mixing competitive and allelopathic cover crop species with maximal total weed suppression ability. It seems that cover crops produce and release more allelochemicals when plants are exposed to stress or physical damage. Avena strigose, for example, showed stronger weed suppression under dry conditions than during a moist autumn. These findings raise the question of whether allelopathy can be induced artificially. © 2019 Society of Chemical Industry     

Polymorphisms in cyanogenic glucoside and cyano‐amino acid content in natural accessions of common vetch (Vicia sativa L.) and selection for improved agronomic performance

Common vetch (Vicia sativa L.) is an important annual forage legume. It is used as a cover crop, green manure, pasture legume and for silage and hay production. Its seeds can be used as a source of highly digestible protein and minerals in animal diets. However, their utilization as a feedstuff for monogastric animals is hindered by the fact that the seeds contain cyanogenic antinutritional factors that reduce their palatability. An effective utilization of V. sativa seeds as a successful monogastric feed stuff requires selection for higher protein availability and minimization of the cyanogenic antinutritional factors content. In this study, we selected one natural accession named Mjez Ibeb, from a collection of 25 accessions and cultivars, based on its superior agronomic performance and its naturally occurring genetic variation for cyanogenic traits. We investigated the genetic variation that exists for the cyanogenesis trait in more detail and analysed the seeds of 133 lines derived from accession Mjez lbeb. Of these, 40 naturally polymorphic lines that showed deficiencies in cyanogenesis and cyano‐amino acid content, were subsequently selected for detailed chemical analysis. Cyanogenic glucosides and cyano‐amino acid concentrations varied widely in the 40 lines. Multivariate analysis was performed and three lines (L₁₆, L₂₁, L₁₈) with low content of cyanogenic compounds were identified.     

Assessment of airborne primary inoculum availability and modelling of disease onset of ascochyta blight in field peas

Ascochyta blight is a serious disease affecting field peas. In France, disease management relies mainly on scheduled chemical applications without taking into account the actual disease risk. A better understanding of the factors affecting disease onset would therefore help in the timing of the first application. Field experiments involving eight sowing dates between mid-September and mid-December were conducted for two consecutive years. The seasonal dynamics of airborne inoculum were investigated through trap plants. The weekly availability of airborne primary inoculum was extremely low during autumn and winter and was partially influenced by mesoclimatic conditions. Disease onset occurred between mid-October and early March depending on the sowing date. Generally, the later the sowing date, the longer the period between sowing and disease onset. This was due to an increase in the period between sowing and emergence. Disease onset was observed 14–35 days after emergence. A disease onset model based on the calculation of weather-dependent daily infection values (DIVs) was established, assuming that disease onset occurs once the temperature and moisture requirements for incubation are met. Cumulative daily infection values (cDIVs) were determined by sowing date and experiment through addition of consecutive DIVs between emergence and disease onset. A frequency analysis of cDIVs was performed to determine the 10th and 90th percentiles of the distribution. An analysis of the observed and predicted values showed that observed disease onset dates were almost always included in the forecast window defined by these two percentiles. This study is the first attempt to predict ascochyta blight onset in field peas and should contribute to development of a more rational fungicide application strategy.     

Wound management in nonpsittacine birds.

Although nonpsittacine avian species comprise many different groups of birds, basic medical and surgical principles common to wound management in many vertebrate species are still applicable. This article will delve into examination and wound assessment along with therapeutic stabilization of wounded nonpsittacine birds. An overview of common case presentations that lead to a necessity for wound care are included, and may focus on one particular avian group, but the information can be used on a variety of avian species.     

ULTRASONOGRAPHIC EVALUATION OF THE PROSTATE IN HEALTHY INTACT DOGS

Sagittal and transverse ultrasonographic images of the prostate gland were obtained in 100 healthy adult intact male dogs. Prostatic length, width, and height on transverse and sagittal images as well as the presence of prostatic cysts were determined. Linear regression and correlation analysis were performed between prostatic parameters (length, width, height on sagittal and transverse images, and estimated volume) and parameters related to body size (body weight, body height, left kidney length and aortic diameter) and age of the dogs. Significant positive correlations were found between all prostatic parameters and parameters related to body size and age. Maximum predicted values for prostatic parameters for a given body weight and age were determined based on the upper limit of the 95% confidence interval of the mean predicted values. Such values should represent a useful tool for ultrasonographic evaluation of the prostate in the dog. Prostatic cysts were found in 14% of the dogs.     

Isolation, Characterization, and Distribution of a Biocontrol Fungus from Cysts of Heterodera glycines

ABSTRACT Seventy-six populations of Heterodera glycines were collected from 33 counties in 10 states of the United States along the Mississippi and Missouri Rivers in 1992 and 1993. A sterile hyphomycete fungus of an unnamed taxon, designated ARF18 and shown to be a parasite of eggs of H. glycines, was isolated from eggs and cysts of 10 of the populations from Kentucky, Louisiana, Mississippi, and Tennessee. Ten isolates of ARF18 obtained in this study and seven isolates obtained in earlier studies were characterized for cultural morphology on several growth media, the ability to produce sclerotium-like structures (SLS) on cornmeal agar, growth rates, pathogenicity to eggs of H. glycines in vitro, and mitochondrial (mt) DNA restriction fragment length polymorphisms (RFLPs). All 17 isolates of ARF18 readily grew on potato dextrose agar, cornmeal agar, and nutrient agar. Based on colony morphology and SLS appearance on cornmeal agar, the isolates could be grouped into two morphological phenotypes. Isolates that produced SLS that were composed of a compact mass of hyphae were designated ARF18-C, whereas isolates that produced SLS composed of a mass of loosely clumped hyphae were designated ARF18-L. Only minor differences in growth rates were detected among the ARF18-C and ARF18-L isolates. All 10 ARF18-C isolates, which were from Arkansas, Louisiana, Mississippi, and Tennessee, belonged to a single mtDNA RFLP haplotype. The seven ARF18-L isolates shared many comigrating mtDNA restriction fragments with one another, but belonged to three distinct mtDNA RFLP haplotypes. Ability to infect eggs of H. glycines in vitro varied considerably among the various isolates of ARF18. In particular, several of the ARF18-C isolates were consistently able to infect over 50% (mean = 70.0%, standard deviation = 16%) of the eggs of H. glycines, whereas ARF18-L infected eggs to a lesser degree (mean = 25%, standard deviation = 27%). ARF18-C was isolated only from H. glycines populations from below 37 degrees N latitude. The presence of ARF18 was associated with soils with Mg levels <314 kg/ha, cyst numbers >4.5 per 100 cm(3), and iron levels >203.5 kg/ha; or with Mg levels >314 kg/ha and Na levels <121 kg/ha. The widespread distribution of ARF18 and the ability of some isolates to aggressively colonize eggs of H. glycines are indications that it has potential as a biological control agent for H. glycines.     

Pathology of the distal condyles of the third metacarpal and third metatarsal bones of the horse

This study examined material from Thoroughbred horses, the majority of which had been in race training, for evidence of pathology in the third metacarpal (McIII) and third metatarsal (MtIII) bones which might be related to the occurrence of distal condylar fractures. Whole bone samples were studied and documented by macrophotography prior to macroradiography and computed tomographic (CT) imaging. Microradiographs were made from 100 microm thick mediolateral sections cut perpendicular to the dorsal and palmar/plantar articular surfaces of distal condylar regions of McIII and MtIII. Blocks were prepared for morphological imaging using the backscattered electron mode of scanning electron microscopy (BSE SEM). Linear defects in mineralised articular cartilage and subchondral bone were found in the palmar/plantar aspects of the condylar grooves adjacent to the sagittal ridge. These were closely related to the pattern of densification of the subchondral bone and were associated with intense focal remodelling of the immediately adjacent and subjacent bone. Parasagittal fractures of the condyles originated in similar defects. A unifying hypothesis for the aetiopathogenesis of these fractures is presented.