Quantity and transmission efficiency of an isolate of the Potato virus Y–Wilga (PVYN−Wi) by aphid species reared on different host plants

Journal of Plant Diseases and Protection - Potato virus Y (PVY) is a destructive plant virus causing important damage in different crops, particularly in potato. PVY is transmitted in a...     

Toxicity of chlorantraniliprole to Cry1Ac-susceptible and resistant strains of Helicoverpa armigera

Transgenic Bt cotton expressing Cry1Ac is important in controlling various agricultural pests, including Helicoverpa armigera. Especially for transgenic crops that are cultivated in large expanses, avoiding resistance development is a key for ensuring sustainability of Bt technologies. Integrated pest management, in which transgenic crops are strategically combined with rational pesticide use, may help to prevent H. armigera resistance acquisition in Bt cotton. In this study, we evaluated the toxicity of a novel insecticide (chlorantraniliprole) on Cry1Ac-susceptible and resistant individuals of H. armigera. More specifically, we assessed the effect of chlorantraniliprole on the activity of two enzymes and conducted laboratory bioassays to determine its toxicity on H. armigera larvae. Chlorantraniliprole increased esterase and glutathione-S-transferase activities in Cry1Ac susceptible and resistant populations of H. armigera. Cry1Ac resistant populations XJ-F (Cry1Ac resistance ratio 21.8-fold), XJ-10.0 (95.8-fold) and BTR (3536.5-fold) did not show cross-resistance to chlorantraniliprole, with LC₅₀ values of 0.0733 (μg/mL) in XJ-F, 0.0545 (μg/ml) in XJ-10.0 and 0.0731 (μg/mL) in BTR, which were close to that in the susceptible strain 96S (0.0954 μg/mL). Our work shows that chlorantraniliprole could be considered to be integrated in Bt cotton management schemes to delay the H. armigera resistance development.     

Endotoxic Shock Part II: A Review of Treatment

Treatment of endotoxemia is difficult because of the numerous mediators involved in the body's response to endotoxin. There are three possible approaches in treating endotoxemia. The interaction of endotoxin with target cells can be blocked by inducing tolerance, decreasing plasma endotoxin concentrations, or interfering with endotoxin binding. Once endotoxin has interacted with target cells, endogenous mediators can be blocked with a huge variety of drugs. The effects of corticosteroids, cyclooxygenase blockers, leukotriene blockers, platelet activating factor blockers, tumor necrosis factor blockers, oxygen radical scavengers, opiate antagonists, antihistamines, calcium channel blockers are detailed. Supportive care of the endotoxemic patient continues to be a critical aspect of treatment. Controversies regarding solutions to use for volume support, vasoactive and cardiostimulant drugs, metabolic support, and treatment of disseminated intravascular coagulation are reviewed.     

Canopy Uptake of 15NH3 by Four Temperate Tree Species and the Interaction with Leaf Properties

Tree canopies are believed to act as a sink of atmospheric ammonia (NH₃). However, few studies have compared the uptake efficiency of different tree species. This study assessed the uptake of ¹⁵N-labelled NH₃ at 5, 20, 50 and 100?ppb_v by leaves and twigs of potted silver birch, European beech, pedunculate oak and Scots pine saplings in June, August and September 2008. Additionally, foliar uptake of ¹³C-labelled carbon dioxide (¹³CO₂) and leaf stomatal characteristics were determined per species and treatment date and the relation with ¹⁵NH₃ uptake and estimated stomatal ¹⁵NH₃ uptake were assessed. Both ¹⁵NH₃ and ¹³CO₂ uptake were affected by tree species and treatment date, but only ¹⁵NH₃ uptake was influenced by the applied NH₃ concentration. Depending on the treatment date, ¹⁵NH₃ uptake by leaves and twigs was highest at 5 (September), 20 (June) or 50 (August) ppb_v. Birch, beech and oak leaves showed the highest uptake in August, while for pine needles this was in June and, except at 5?ppb_v in June, the ¹⁵NH₃ uptake was always higher for the deciduous species than for pine. For all species except beech ¹³CO₂ uptake was highest in August and on every treatment date the ¹³CO₂ uptake by leaves of deciduous species was significantly higher than by pine needles. Leaf characteristics and ¹³CO₂ uptake did not provide a strong explanation for the observed differences in ¹⁵NH₃ uptake. This study shows that on the short-term a high interspecific variability exists in NH₃ uptake, which depends on the time in the growing season.     

Effective biological control of an invasive mealybug pest enhances root yield in cassava

Insects provide critical ecosystem services to humanity, including biological control of pests. Particularly for invasive pests, biological control constitutes an environmentally sound and cost-effective management option. Following its 2008 invasion of Southeast Asia, biological control was implemented against the cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae) through the introduction and subsequent release of the host-specific parasitoid Anagyrus lopezi (Hymenoptera: Encyrtidae) in Thailand. In this study, we quantify yield benefits of mealybug biological control in Thailand’s cassava crop by using two different types of manipulative field trials: i.e., ‘physical exclusion’ cage trials and field-level ‘chemical exclusion’ assays. In cage trials with two popular cassava varieties, root yield and total dry matter (or ‘biological yield’) were a respective 4.0–4.2 times and 3.5–3.9 times higher in the presence of biological control. Extrapolating results from cage trials, biological control thus ensured an approximate yield gain of 5.3–10.0 T/ha for either variety. Under chemical exclusion trials, P. manihoti populations attained levels of 3266?±?1021 cumulative mealybug-days (CMD) over a 10-month time period, and no longer impact yields. Moreover, under effective P. manihoti control, both root yield and biological yield increased with season-long CMD measures, and pest management interventions-including insecticide sprays-led to notable reductions in yield. This study is the first to show how biological control effectively downgrades the globally invasive P. manihoti to non-economic status and restores yields in Thailand’s cassava crop. Our work emphasizes the economic value of biological control, reveals how current P. manihoti populations do not necessarily cause yield penalties, and underlines the central importance of nature-based approaches in intensifying global agricultural production.     

Potentials and Limitations of Existing Forecasting Models for <Emphasis Type="Italic">Alternaria</Emphasis> on Potatoes: Challenges for Model Improvement

Alternaria species, including A. solani and A. alternata, are a serious threat to potato cultivation and cause necrotic leaf spots, leading to premature defoliation and yield losses. To reduce the impact of the disease, a timely prediction of a disease outbreak is important. Worldwide, modelling attempts have been made to predict the occurrence of Alternaria in order to take adequate measures. In the present paper, we made an effort to classify the existing prediction models and subdivided them into three categories: plant-based, pathogen-based and plant-pathogen-based models. Plant-based models predict the susceptibility of the host crop and presume that Alternaria inoculum is abundantly present and not the restrictive factor, whereas pathogen-based models consider one or more stages of the Alternaria life cycle and suppose that the host crop is always susceptible. The plant-pathogen-based models try to take into account the complete plant-pathogen-environment relationship. In this paper, a critical review of the described models for Alternaria leaf spot is presented. To illustrate the discrepancy between the predicted and the observed dates of the first Alternaria symptoms or the discrepancy between the suggested first treatment and necessity to treat Alternaria, the existing models were subjected to the Belgian weather conditions. It turns out that these models are not applicable in Belgium or similar regions. This can be partially attributed to the fact that most of the currently available models are too simplistic (only plant- or pathogen-based) for regions where the disease pressure highly fluctuates between growing seasons and between locations within one season. Finally, perspectives for model improvement are given taking into account both plant, pathogen and environment.     

Color and albedo heterogeneity of Vesta from Dawn

Multispectral images (0.44 to 0.98 μm) of asteroid (4) Vesta obtained by the Dawn Framing Cameras reveal global color variations that uncover and help understand the north-south hemispherical dichotomy. The signature of deep lithologies excavated during the formation of the Rheasilvia basin on the south pole has been preserved on the surface. Color variations (band depth, spectral slope, and eucrite-diogenite abundance) clearly correlate with distinct compositional units. Vesta displays the greatest variation of geometric albedo (0.10 to 0.67) of any asteroid yet observed. Four distinct color units are recognized that chronicle processes--including impact excavation, mass wasting, and space weathering--that shaped the asteroid's surface. Vesta's color and photometric diversity are indicative of its status as a preserved, differentiated protoplanet.