Modeling the invasive emerald ash borer risk of spread using a spatially explicit cellular model

The emerald ash borer (EAB, Agrilus planipennis) is decimating native ashes (Fraxinus sp.) throughout midwestern North America, killing millions of trees over the years. With plenty of ash available throughout the continent, the spread of this destructive insect is likely to continue. We estimate that the insect has been moving along a “front” at about 20 km/year since about 1998, but more alarming is its long-range dispersal into new locations facilitated by human activities. We describe a spatially explicit cell-based model used to calculate risk of spread in Ohio, by combining the insect’s flight and short-range dispersal (“insect flight”) with human-facilitated, long-range dispersal (“insect ride”). This hybrid model requires estimates of EAB abundance, ash abundance, major roads and traffic density, campground size and usage, distance from the core infested zone, wood products industry size and type of wood usage, and human population density. With the “insect flight” model, probability of movement is dependent on EAB abundance in the source cells, the quantity of ash in the target cells, and the distances between them. With the “insect-ride” model, we modify the value related to ash abundance based on factors related to potential human-assisted movements of EAB-infested ash wood or just hitchhiking insects. We attempt to show the advantage of our model compared to statistical approaches and to justify its practical value to field managers working with imperfect knowledge. We stress the importance of the road network in distributing insects to new geographically dispersed sites in Ohio, where 84% were within 1 km of a major highway.     

Smallholder cotton production in sub-Saharan Africa: An assessment of the way forward

Abstract

The benefits of growing organic cotton were advocated in a recent contribution to this Forum. While welcoming a debate on this subject, we advocate a closer look at the history of cotton in Africa, whereby for decades farmers did grow cotton without insecticides. We believe that while there may be a market for ‘organic’ cotton production, it would be a retrograde step to ignore the technological advances that enable much higher yields to be obtained economically. What is needed is improved training and extension services backed up by an on-going research programme for IPM/ICM utilising the most appropriate technologies. Continuing research is needed to integrate new technology of benefit to the small-scale farmer, whether aiming at organic production or higher yields by integrating rational use of biotechnology and pesticides.     

Investigating the effects of wettability and pore size distribution on aggregate stability: the role of soil organic matter and the humic fraction

Soil organic matter (SOM) is an important factor influencing aggregate stability. Interactions between SOM and soil structure are widely studied, although the subtle relationship between SOM content, pore size distribution and aggregate stability is not fully known. Here we investigate such a relationship by means of a long‐term experiment established in 1962 in northeastern Italy, which considers different fertilizer practices (organic, mineral and mixed) applied to a continuous maize crop rotation. We measured wet stability of 1–2 mm aggregates subjected to different pretreatments. Both soil physical properties (such as pore size distribution and hydrophobicity) and chemical properties (soil organic and humic carbon content) affecting aggregate stability were considered. The chemical structure of humic substances was characterized by thermal and spectroscopic analyses (TG‐DTA, DRIFT and ¹H HR MAS NMR). The Pore‐Cor network model was then applied to evaluate the contribution of hydrophobicity and porosity to aggregate wetting. Our study suggests that SOM and its humic fraction can affect aggregate wetting and consequently slaking by modifying the pore size distribution with a shift from micropores (5–30 µm) and mesopores (30–75 µm) to ultramicropores (0.1–5 µm); hydrophobicity was also increased as a result of different humic composition. Spectroscopic analysis showed that hydrophobic compounds were mostly associated with complex humic molecules. Models of fast wetting dynamics, however, suggest that the contribution that hydrophobicity makes to aggregate stability, especially to soils with large carbon inputs, may not be the most significant factor.     

The use of plant growth regulators in micropropagation of slow-growing potato cultivars

Summary The growth in vitro of several potato cultivars (Désirée, Record, Foxton, Golden Wonder) on media containing plant growth regulators has been studied with a view to accelerating micropropagation of slow-growing cultivars. Whilst 1 mg/l GA₃ substantially increased the height of plantlets of most cultivars, the combination of 1 mg/l GA₃+0.1 mg/l NAA was more effective in increasing the number of nodes which could subsequently be cultured. Using this medium, slow-growing cultivars could be multiplied more rapidly than on basic Murashige and Skoog medium. Cultivars showed wide variation in their response to some plant regulators.

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Zusammenfassung Bei vier Kartoffelsorten (Désirée, Record, Foxton, Golden Wonder) wurde das in vitro Wachstum auf Medien mit verschiedenen Pflanzenwachstumsregulatoren im Hinblick auf eine Beschleunigung der Mikrovermehrung langsam wachsender Sorten untersucht. Auf dem N?hrmedium nach Murashige und Skoog zeigten Sorten auff?llige Unterschiede in den Wachstumsraten (Tab. 1). Die schnelle Vermehrung kurzwüchsiger Sorten war schwierig, weil sie oft kurze, weniger als 2 mm lange Nodienabschnitte hervorbrachten, bei denen meistens das Wachstum versagte. Die Zugabe von 1 mg/l GA zum N?hr-medium vergr?sserte zwar die H?he der Pfl?nzchen, insbesondere bei den kurzwachsenden Sorten Record und Foxton, erh?hte aber die Anzahl der verwendbaren Nodien (2 mm oder l?nger) nur geringfügig. Désirée reagierte nur wenig auf die GA-Zugabe (Tab. 2). 1 mg/l GA+0,1 mg/l NAA verursachte bei allen Sorten einen viel gr?sseren Zuwachs bei der H?he und der Anzahl verwendbarer Nodien. W?hrend GA allein normalerweise nur die Verl?ngerung der unteren Internodien stimulierte, verursachten GA+NAA zusammen die Verl?ngerung nahezu aller Internodien (Tab. 3). BA (0,1 mg/l) bewirkte mit Ausnahme bei Golden Wonder und in nur geringem Masse bei Désirée keine Vergr?sserung der Internodienl?nge, aber in Kombination mit GA war die Wirkung besser als bei GA allein. CCC (500 mg/l) verursachte eine erhebliche Reduktion der H?he. Die Kombination GA+NAA war im Hinblick auf die Zunahme der H?he und der Anzahl der verwendbaren Nodien am wirkungsvollsten, und ihre Verwendung würde die Vermehrung langsam wachsender Sorten beschleunigen. Die Kombinationen GA+NAA bzw. GA+BA mit CCC brachten keine weiteren Vorteile (Tab. 4).

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Résumé La culture in vitro de quatre variétés de pommes de terre (Désirée, Record, Foxton et Golden Wonder) a été étudié sur milieu contenant des régulateurs de croissance, afin d'accélérer la micropropagation des variété à croissance lente. Des différences importantes de taux de croissance ont été observées entre variétés cultivées sur milieu de Murashige et Skoog (tabl. 1). Les variétés courtes ne peuvent être multipliées rapidement car elles produisent quelques entrenoeuds inférieurs à 2 mm dont la croissance est le plus souvent impossible. L'adjonction d'1 mg/l GA au milieu nutritif accro?t la longueur des plantules en particulier pour les variétés courtes Record et Foxton, mais n'augmente que très faiblement le nombre de noeuds utilisables (2 mm et plus). GA a peu d'effet sur Désirée (tabl. 2). L'adjonction d'1 mg/l GA+0,1 mg/l NAA augmente davantage la hauteur et le nombre de noeuds utilisables sur toutes les variétés. GA et NAA provoquent une élongation de la plupart des entrenoeuds (tabl. 3) tandis que GA seul stimule l'élongation des entrenoeuds inférieurs. A l'exception de Golden Wonder et dans une moindre mesure Désirée, aucune élongation n'a été observée avec BA (0,1 mg/l) mais son association avec GA a donné un meilleur résultat que GA seul. CCC (500 mg/l) a provoqué une forte réduction de la hauteur. Le traitement GA+NAA a été le plus efficace, tant sur la longueur des noeuds utilisables que sur leur nombre et devrait ainsi permettre une accélération de la multiplication des variétés à croissance lente. Aucune amélioration n'a été obtenue en associant GA+NAA ou GA+BA au CCC (tabl. 4).

     

Use of diagnostic markers to monitor fasciolosis and gastrointestinal nematodes on an organic dairy farm

A 12-month study was conducted to assess and monitor gastrointestinal tract nematodes and liver fluke in cohorts of cattle on a Scottish organic dairy farm. Various diagnostic markers for helminth parasites of cattle from different age groups were assessed monthly from April 2007 to March 2008. First season grazing stock were subjected to significant challenge from Ostertagia ostertagi nematodes as reflected in serum pepsinogen concentrations, which rose markedly in the second half of the grazing season. In addition, plasma albumin concentrations decreased and faecal egg counts (FEC) increased moderately, indicating exposure to both O ostertagi and probably Cooperia oncophora. Second season grazing animals had a peak FEC early in the grazing period, suggestive of a potential carry-over of Ostertagia species infection ('Type 2') during housing. All classes of cattle showed evidence of fluke (Fasciola hepatica) infection. Adult cow exposure to O ostertagi and fluke was estimated via the use of ELISA testing to detect antibodies to O ostertagi and F hepatica and the high levels detected suggested a significant exposure response. Despite low stocking densities and sympathetic grazing management, there was a significant challenge to all grazing stock from gastrointestinal nematodes and liver fluke.     

Facing the threat of equine parasitic disease

Horses worldwide are exposed to a complex mixture of intestinal parasitic helminths. When burdens are high, these parasites can seriously compromise health and welfare. Some helminth species have an extremely high prevalence and are difficult to control, not least because there is a limited understanding of their most basic biology. Furthermore, levels of resistance to some of the commonly used anthelmintics are widespread and increasing. The cyathostomins are the most common nematode species affecting equids worldwide. Within this group of parasites are more than 50 different species. Until recent research activities, little was known about the contribution that individual species make to clinical disease, parasite epidemiology and anthelmintic resistance. This review describes some of the recent research advances in the understanding of cyathostomins in these areas. As part of the research effort, molecular tools were developed to facilitate identification of the non-parasitic stages of cyathostomins. These tools have proved invaluable in the investigation of the relative contributions that individual species make to the pathology and epidemiology of mixed infections. At the more applied level, research has also progressed in the development of a diagnostic test that will allow numbers of cyathostomin encysted larvae to be estimated. This test utilises cyathostomin-specific serum antibody responses as markers of infection. As anthelmintic resistance will be the major constraint on parasite control in future, researchers are actively investigating mechanisms of drug resistance and how to improve the detection of resistance in the field. Recent developments in these areas are also outlined.     

Circulating melanin-containing cells and neutrophils with phagocytized melanin granules in a horse with disseminated melanoma

An 18-year-old, grey, Thoroughbred Cross gelding was referred to the Cummings School of Veterinary Medicine at Tufts University following a 3-week history of low-grade fever of unknown origin, distal limb swelling, and weight loss. Clinical examination identified a few black, round, smooth nodules along the ventral aspect of the proximal tail. Transabdominal ultrasound showed a markedly enlarged heterogenous spleen, hyperechoic liver nodules, and evidence of peritonitis with fibrin deposition. A mature neutrophilia was noted on complete blood count with variable numbers of phagocytized granules within neutrophils. The granules did not stain with Perl's Prussian blue, and were intensely positive when stained with Fontana-Mason, consistent with melanin. On necropsy, the spleen occupied approximately one-third of the abdominal cavity and was diffusely firm with abundant black pigment on cut section. The medullary space of the 18th thoracic vertebra was also diffusely blackened. The splenic, mediastinal, and tracheobronchial lymph nodes were five times the normal size and diffusely pigmented. The final anatomic diagnosis was disseminated malignant melanoma with extensive splenic involvement and hemolymphatic and vascular neoplastic dissemination. To the authors' knowledge, this is the first full report to identify circulating neutrophils containing phagocytized melanin granules, which confirmed an antemortem diagnosis of disseminated melanoma.     

Advancement of noble metallic nanoparticles in agriculture: A promising future

Since the last decades, nanotechnology has gained the attention of researchers in the field of plant sciences. The characteristics of nanoparticles are reliant on their shape and size. Formulations involving noble metallic nanoparticles(NMNPs) offer novel technologies to boost agricultural productivity and minimize conventional pesticide use. The application of nanoparticles as nanofertilizer improves plant growth and enhances nutrient uptake efficiency. Noble metallic nanoparticles act as antim...