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We investigated the antifungal activities of an endophytic fungus identified as Acaromyces ingoldii, found on a loblolly (Pinus taeda L.) pine bolt in Louisiana during routine laboratory microbial isolations. The specific objectives were to determine the inhibitory properties of A. ingoldii secondary metabolites (crude extract) on the mycelial growth of a brown-rot fungus Gloeophyllum trabeum and a white-rot fungus Trametes versicolor, and to determine the effective concentration of A. ingoldii crude preparation against the two decay fungi in vitro. Results show the crude preparation of A. ingoldii from liquid culture possesses significant mycelial growth inhibitory properties that are concentration dependent against the brown-rot and white-rot fungi evaluated. An increase in the concentration of A. ingoldii secondary metabolites significantly decreased the mycelial growth of both wood decay fungi. G. trabeum was more sensitive to the inhibitory effect of the secondary metabolites than T. versicolor. Identification of specific A. ingoldii secondary metabolites, and analysis of their efficacy/specificity warrants further study. Findings from this work may provide the first indication of useful roles for Acaromyces species in a forest environment, and perhaps a future potential in the development of biocontrol-based wood preservation systems. more...

The camphor shot borer, Cnestus mutilatus (Blandford) is a nonnative ambrosia beetle first reported in the United States in 1999 at Oktibbeha County in Mississippi. Although, C. mutilatus is a major pest of several trees in its native habitat in Asia, it is not yet a major pest in the United States. However, the range expansion in recent years across the southeastern region indicates that C. mutilatus could be adapting quickly to the new environment, perhaps because of the availability of numerous host trees and suitable environmental conditions that support the population. As the population increases, future outbreaks of C. mutilatus may result in mortality of valuable hosts. Our objective was to identify potential suitable habitats for C. mutilatus in the southeastern United States under changing climate by 2020 and 2060 by examining C. mutilatus preferred conditions, host environmental requirements, precipitation, and temperature projections from an ensemble of general circulation model, and Intergovernmental Panel on Climate Change future climate scenarios. Our results indicated that suitable habitat for C. mutilatus in the southeastern United States will expand slightly under the A1B emission scenarios (i.e., moderate population growth and high-energy use balanced across all sources), and significantly under B1 emission scenarios (i.e., representing moderate population growth and an emphasis on global approaches to economic and environmental stability) by 2060. Whereas the opposite may occur under the A2 scenario (i.e., representing continuously increasing population, regionally focused economic growth, and slower introduction of alternative fuels technology). Nearly half of the parishes in Louisiana and counties in Mississippi will be suitable for C. mutilatus by 2020, under the A2 emission scenarios. However, suitable habitat range could decrease and become fragmented by 2060. These results could be useful in forest management efforts in places where C. mutilatus may become established in the future. more...

The woodwasp Sirex noctilio F. (Hymenoptera: Siricidae) has become established in North America.Aprimary tactic for the management of S. noctilio in the southern hemisphere has been the development of a biological control agent, Deladenus siricidicola Bedding. This nematode has a bicyclic life cycle including a mycetophagous free-living and parasitic cycle. During oviposition, female Sirex woodwasps inject a symbiotic fungus. Because D. siricidicola only develops well on Amylostereum areolatum (Chaillet ex Fries) Boidin (Russulales: Amylostereaceae) and North American woodwasps were thought to all have Amylostereum chailletii (Persoon) Boidin as their fungal symbiont, the risk of unintended impacts from D. siricidicola in North America was considered low. Specific polymerase chain reaction primers were designed to amplify the intergenic spacer region of Amylostereum symbionts in a population of the native woodwasp Sirex nigricornis F. located in central Louisiana (i.e., well outside the known dis... more...

In the southeastern United States, millions of dollars worth of crop damage associated with tobacco thrips (Frankliniella fusca Hinds) and western flower thrips (Frankliniella occidentalis Pergande) are reported annually for economically important crops such as cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.). Tobacco thrips and western flower thrips are also important vectors of Tomato spotted wilt virus (TSWV). The populations and spread of both thrips species relies on favourable weather conditions, especially prolonged temperatures above a minimum developmental threshold. Accurate local weather information is, therefore, crucial for early prediction of thrips' population dynamics during the spring when thrips' population information could assist farmers in mitigating damage to crops. The objective of this study was to demonstrate the application of the Weather Research and Forecasting (WRF) model predictions for developing high resolution spatial and temporal forecast maps of favourable conditions for thrips' development even for locations where weather stations are not available. Tobacco thrips and western flower thrips were evaluated based on degree-day models. The results showed that southwestern Georgia is more favourable for thrips development during the early part of the growing season, although the rate of development varied according to the thrips species. The maps that were produced using WRF output provided high-resolution forecasts for favourable conditions and scouting guidance in places where weather information was limited. An accurate prediction of pest development based on forecasts of favourable conditions may assist growers in pest management decisions and in timely application of insecticides. more...

Peanut growers in the southeastern United States have suffered significant economic losses due to spotted wilt caused by Tomato spotted wilt virus (TSWV). The virus is transmitted by western flower thrips, Frankliniella occidentalis, and tobacco thrips, F. fusca, and was first reported in the southeast in 1986. The severity of this disease is extremely variable in individual peanut fields, perhaps due to the sensitivity of the vector population to changing weather patterns. The objective of this study was to investigate the impact of early spring weather on spotted wilt risk in peanut. On-farm surveys of spotted wilt severity were conducted in Georgia peanut fields in 1998, 1999, 2002, 2004, and 2005. The percent spotted wilt intensity (%) for cv. Georgia Green was recorded and categorized into three intensity levels: low, moderate, and high. Meteorological data were obtained from the Georgia Automated Environmental Monitoring Network for the period between March 1 and April 30. Statistical analysis was conducted to identify weather variables that had significant impact on spotted wilt intensity. The results indicated a high probability of spotted wilt if the number of rain days during March was greater than or equal to 10 days and planting was before 11 May or after 5 June. The total evapotranspiration in April (>127 mm) and the average daily minimum temperature in March (>6.8°C) similarly increased the risk of spotted wilt. Knowing in advance the level of spotted wilt risk expected in a peanut field could assist growers with evaluating management options and significantly improve the impact of their decisions against spotted wilt risk in peanut. more...

This chapter examines experimental design considerations for a population-based approach for identifying microorganisms involved in specific in situ functions. Although this chapter focuses on a particular population-based approach, many of the experimental design considerations discussed here apply to a wide range of rRNA gene-based population studies and sequence selective PCR assays. This chapter examines an experimental approach that uses the population-based strategy. The approach has the following three phases: (i) identifying populations of rRNA genes whose abundances correlate with the functional parameter, (ii) validating the rRNA gene correlates identified in phase I by using an independent quantitative assay, and (iii) isolating the microorganisms identified by the rRNA gene correlates and reintroducing them into the environment to assess their functions in situ. This approach was recently used to identify microorganisms that suppress the population development of the plant parasitic nematode Heterodera schachtii in southern California soil. Functional gradients are created by manipulating the microbial community with methods such as differential heat treatments, targeted antimicrobial agents, and nutritional amendments. Microbial community composition is examined by rRNA gene analysis. Nucleotide sequence analysis of rRNA gene clone libraries can be used to generate detailed depictions of microbial community composition. PCR assays can be validated by using them to amplify DNAs extracted from different environmental samples and then cloning and sequencing several randomly selected clones from each sample. The assays can be considered selective if they exclusively amplify the target sequence. more...