Insecticide resistance,control failure likelihood and the First Law of Geography

Insecticide resistance is a broadly recognized ecological backlash resulting from insecticide use and is widely reported among arthropod pest species with well‐recognized underlying mechanisms and consequences. Nonetheless, insecticide resistance is the subject of evolving conceptual views that introduces a different concept useful if recognized in its own right – the risk or likelihood of control failure. Here we suggest an experimental approach to assess the likelihood of control failure of an insecticide allowing for consistent decision‐making regarding management of insecticide resistance. We also challenge the current emphasis on limited spatial sampling of arthropod populations for resistance diagnosis in favor of comprehensive spatial sampling. This necessarily requires larger population sampling – aiming to use spatial analysis in area‐wide surveys – to recognize focal points of insecticide resistance and/or control failure that will better direct management efforts. The continuous geographical scale of such surveys will depend on the arthropod pest species, the pattern of insecticide use and many other potential factors. Regardless, distance dependence among sampling sites should still hold, following the maxim that the closer two things are, the more they resemble each other, which is the basis of Tobler's First Law of Geography. © 2016 Society of Chemical Industry     

Cover Image,Volume 73, Issue 1

The cover image, by Oscar Fernando Santos‐Amaya et al., is based on the Research Article Fitness costs and stability of Cry1Fa resistance in Brazilian populations of Spodoptera frugiperda, DOI: 10.1002/ps.4312 . Photo Credit: Dr. Oscar Santos‐Amaya.

     

Identifying resistance gene analogs associated with resistances to different pathogens in common bean

ABSTRACT A polymerase chain reaction approach using degenerate primers that targeted the conserved domains of cloned plant disease resistance genes (R genes) was used to isolate a set of 15 resistance gene analogs (RGAs) from common bean (Phaseolus vulgaris). Eight different classes of RGAs were obtained from nucleotide binding site (NBS)-based primers and seven from not previously described Toll/Interleukin-1 receptor-like (TIR)-based primers. Putative amino acid sequences of RGAs were significantly similar to R genes and contained additional conserved motifs. The NBS-type RGAs were classified in two subgroups according to the expected final residue in the kinase-2 motif. Eleven RGAs were mapped at 19 loci on eight linkage groups of the common bean genetic map constructed at Centro Internacional de Agricultura Tropical. Genetic linkage was shown for eight RGAs with partial resistance to anthracnose, angular leaf spot (ALS) and Bean golden yellow mosaic virus (BGYMV). RGA1 and RGA2 were associated with resistance loci to anthracnose and BGYMV and were part of two clusters of R genes previously described. A new major cluster was detected by RGA7 and explained up to 63.9% of resistance to ALS and has a putative contribution to anthracnose resistance. These results show the usefulness of RGAs as candidate genes to detect and eventually isolate numerous R genes in common bean.     

Preparation and characterization of polyclonal and monoclonal antibodies against Lawsonia intracellularis.

Proliferative enteropathy is an intestinal infectious disease caused by the obligate intracellular bacterium Lawsonia intracellularis. Immunohistochemistry staining has superior sensitivity over hematoxylin and eosin and silver staining for detecting L. intracellularis in histological sections. A L. intracellularis-specific monoclonal antibody (MAb) produced in the UK (IG4 MAb) has been described in the literature. However, no monoclonal or polyclonal antibodies are commercially available. Therefore, the objective of this study was to produce and characterize new polyclonal and monoclonal antibodies against L. intracellularis that are suitable for diagnostic use. The new monoclonal (2001 MAb) and polyclonal antibodies (1999 PAb) were compared with the IG4 MAb using Western blot analysis of outer membrane proteins (OMPs) of 6 L. intracellularis isolates, Bilophila wadsworthia and Brachyspira hyodysenteriae and using immunohistochemistry of known positive and negative histologic samples and pure cultures of L. intracellularis, B. wadsworthia, B. hyodysenteriae, Salmonella choleraesuis, S. typhimurium, and Escherichia coli K88. Immunogold staining using 2001 MAb was performed to show the specificity of the antibody against an L. intracellularis surface protein. Western blot analysis showed that the 2001 MAb targeted an OMP of 77 kD, which made it different from the IG4 MAb that targeted an 18-kD OMP. The immunogold stain demonstrated the specificity of the 2001 MAb to a surface protein of L. intracellularis. The polyclonal antibody (1999 PAb) targeted 5 OMPs (77, 69, 54, 42, and 36 kD). Both the 2001 MAb and 1999 PAb stained known positive, but not negative, histologic samples. Both the 2001 MAb and 1999 PAb reacted with a pure culture of L. intracellularis but not with any other common enteric pathogens. These two new antibodies will be useful for immunodiagnosis of L. intracellularis.     

Hematology of free-living marsh deer (Blastocerus dichotomus) from southeast Brazil.

This work reports basic hematologic values of a sample of a population of free-living marsh deer (Blastocerus dichotomus) living by the Paraná River in Southeast Brazil. Hematologic values are presented separately for male, female, and young animals as well as for anesthetized and nonanesthetized cervids. Nonanesthetized deer restrained by physical means had significantly higher erythrocyte indices and total leukocyte counts. Comparisons of blood parameters of anesthetized animals of different ages and gender differed slightly, with only two significant differences observed: young animals had significantly higher red blood cell counts than adult males and a lower blood total protein content when compared to adult females. Results indicate that two main reference ranges for blood values should be considered for marsh deer, for blood obtained from anesthetized or physically restrained individuals.     

Thoracoscopic pericardiectomy: A feasibility study and impact on cardiac volumetry in healthy horses

This study was conceived to evaluate the feasibility of a thoracoscopic technique intended for partial pericardiectomy in horses and how cardiac volumes are influenced by such procedure in an immediate and mid-term perspective. Thoracoscopic pericardiectomy, which is known as a minimally invasive technique, was performed in six healthy horses. Echocardiographic evaluation was performed in every horse at different times, before and after the procedure. According to the area-length method, the following parameters were evaluated: maximum left atrial volume, minimum left atrial volume, left ventricular volume in systole and left ventricular volume in diastole. These variables were used to calculate the ejection fraction of the left atrium and left ventricle. After 28 days, repeated thoracoscopy was performed to inspect the thoracic cavity. Pericardiectomy was successfully performed in all horses, with post-operative complication documented in only one animal. After 28 days, adhesion was observed in two animals, located between the epicardium and the thoracic wall, without however impairing cardiac function. Pericardial window was broad and well delimited in all horses, without impairing cardiac function. The thoracoscopic pericardiectomy was feasible in all horses. Although a mild reduction in cardiac volumes was documented in the first 72 h after surgery, the procedure did not impair cardiac filling and emptying in the mid-term perspective. Future studies are warranted to investigate how this technique performs in horses with pericardial diseases.     

Equine Proliferative Enteropathy Caused by Lawsonia intracellularis in a Foal in Brazil

An 8-month-old foal in Brazil presented with fever, colic, diarrhea, hypoproteinemia (especially hypoalbuminemia), leukocytosis, and hyperfibrinogenemia and became lethargic and anorexic with a poor body score. A diagnosis of Lawsonia intracellularis proliferative enteropathy was confirmed by fecal polymerase chain reaction and serologic testing, and the foal was successfully treated with oxytetracycline followed by azithromycin.