Biology,Epidemiology and Management of Rhizoctonia solani on Potato

Black scurf and stem canker on potato is an economically important disease complex, causing both quantitative and qualitative damage to potato crops which occurs in potato production areas throughout the world. The ribosomal DNA internal transcribed spacer sequence analysis is currently accepted and a commonly used method for classifying Rhizoctonia species and anastomosis groups (AGs). To date, 13 AGs have been recognized. The updated AG distribution in potato worldwide production areas confirm the status of AG‐3 as the most prevalent AG in potato and reflects the population dynamics of the pathogen probably due to global trading of tubers. As R. solani is a tuber‐ and soilborne pathogen, the ability to detect its levels in the seed tubers and in the soil and predict the potential damage is an important factor in controlling the disease. Effective disease management of Rhizoctonia disease requires implementation of an integrated disease management approach and knowledge of each of its stages. Although the most important control measures are cultural, chemical control (either by seed tuber‐ or in‐furrow treatments) is still an important tool in reducing the damages caused by R. solani.     

Influence of Corn Residue Harvest Management on Grain,Stover, and Energy Yields

Economic, environmental, and energy independence issues are contributing to rising fossil fuel prices, petroleum supply concerns, and a growing interest in biomass feedstocks as renewable energy sources. Potential feedstocks include perennial grasses, timber, and annual grain crops with our focus being on corn (Zea mays L.) stover. A plot-scale study evaluating stover removal was initiated in 2008 on a South Carolina Coastal Plain Coxville/Rains–Goldsboro–Lynchburg soil association site. In addition to grain and stover yields, carbon balance, greenhouse gas (GHG) emissions and soil quality impact reported elsewhere in this issue, variation in gross energy distribution within various plant fractions — whole plant, below ear shank (bottom), above ear shank (top), cob, as well as leaves and stems of the bottom and top portions (n _{(part, year)}?=?20) was measured with an isoperibol calorimeter. Stalks from above the ear shank were the most energy dense, averaging 18.8 MJ/kg db, and when combined with other plant parts from above the ear shank, the entire top half was more energy dense than the bottom half — 18.4 versus 18.2 MJ/kg db. Gross energy content of the whole plant, including the cob, averaged 18.28?±?0.76 MJ/kg db. Over the 4 years, partial to total removal (i.e., 25 % to 100 %) of above-ground plant biomass could supply between 30 and 168 GJ/ha depending upon annual rainfall. At 168 GJ/ha, the quantity of corn stover biomass (whole plant) available in a 3,254-km² area (32 km radius) around the study site could potentially support a 500-MW power plant.     

153 Invasive Macroalgae on Tropical Reefs: Impacts, Interactions, Mechanisms and Management

Histories, patterns of introduction, management of impacts and predictable futures? Ecological impacts of weedy introduced and native marine algae have set Hawai'i apart from elsewhere in the tropics and offers a new show case for macroalgal blooms. Partly because of our isolation, impacts of non-indigenous species have been clearly identified, in some cases almost as quickly as introductions have occurred to Hawai'i. While hull fouling or intentional introductions may have been initial mechanisms for macroalgal introductions, spread among the Hawaiian Islands is not necessarily linked to the vector for arrival. Further, impacts of non-indigenous species are also not fully predictable, prior to introduction. This situation leads to challenging gaps in management strategies because few generalizations about the roles of nutrients or herbivory as drivers for macroalgal blooms can be supported at this time. Weedy native species represent a wide range of alternate impacts with other apparent combinations of forcing functions. Case histories for the most significant non-indigenous and weedy native algae will be presented with emphasis on potential new criteria to assess ecological impacts and provide resource biologists with critical new tools for the management of reef ecosystems.     

Theme section on “Mesophotic Coral Ecosystems: Characterization, Ecology, and Management”

Mesophotic coral ecosystems (MCEs) are characterized by the presence of light-dependent corals and associated communities that are typically found at depths ranging from 30 to 40 m and extending to over 150 m in tropical and subtropical regions. The dominant communities providing structural habitat in the mesophotic zone can be comprised of coral, sponge, and algal species. Because working in this depth range is constrained by traditional SCUBA limits, less is known about corals and associated organisms there compared to shallower coral communities. Following the first-ever gathering of international scientists to review and discuss existing knowledge of MCEs, this issue focuses on the ecological characterization, geomorphology, and concept of MCEs as refugia for shallow-water populations. The review and research papers comprising this special issue reflect the current scientific understanding of these ecosystems and the underlying mechanisms that regulate them, as well as potential resource management implications. It is important to understand the value and role of mesophotic coral ecosystems in tropical and subtropical regions as these areas face increasing environmental change and human impacts     

Wildfire Smoke,Fire Management,and Human Health

Burning landscapes under controlled conditions to reduce the risk of wildfires is a controversial land management practice. The health risks of smoke generated from controlled burning relative to wildfire remain uncertain. Recent work in the Australian monsoon tropics provided a unique opportunity to study the health effects of smoke pollution at and well below national air quality standards. It found that for each increase in the atmospheric mass of particles 10 g or less in aerodynamic diameter (PM₁₀) per cubic meter of air per 24-hour period, there was a 26% increase in daily asthma presentations to the emergency department of the Royal Darwin Hospital, with an apparent threshold at 40 g/m³ PM₁₀ (lower than the Australian PM₁₀ air quality standard of 50 g/m³). This finding was unaffected by adjusting for weekly rates of influenza, weekday vs. weekends, and school holiday periods. Although further research is being undertaken to substantiate these findings, the upshot of the study suggests that for airsheds containing large human populations, fire managers should strive to keep smoke pollution less than 40 g/m³ PM₁₀.     

Marine Renewable Energies: Opportunities,Law, and Management

Marine renewable energies are still at a very incipient stage. Even so, it can be anticipated that if such energies were to be developed, multiple benefits could be achieved in the environmental, social, and economic spheres. However, these benefits are not without possible controversial aspects. This article examines the content and scope of the applicable international law of the sea regarding the use of renewable energy from the seas.