Simulated Rainfall and Mowing Impact Fungicide Performance When Targeting Dollar Spot in Creeping Bentgrass.

In this 2-year field study, four chemically diverse fungicides (i.e., chlorothalonil, boscalid, iprodione, and propiconazole) were evaluated for their ability to control dollar spot (Sclerotinia homoeocarpa) in creeping bentgrass (Agrostis stolonifera) as affected by simulated rain and mowing timing. Simulated rain (25 to 32 mm) was imposed about 30 min after fungicide application and was compared to rain-free plots. One set of plots was mowed in the morning when the canopy was wet with dew and compared to plots that were mowed when the canopy was dry in the afternoon. The percent reduction in dollar spot control associated with simulated-rain versus rain-free treatments in 2007 and 2008, respectively, was as follows: chlorothalonil 67 and 83%; propiconazole 42 and 79%; boscalid 48 and 70%; and iprodione 33 and 66%. When disease pressure was low, all fungicides subjected to simulated rain provided effective dollar spot control for 7 or more days following the initial application in each year. Across all fungicide-treated plots over 2 years, the average percent reduction in dollar spot associated with morning mowing ranged from 54 to 65%. The reduction in dollar spot severity in morning-mowed plots improved the performance of all fungicides.

Folate status and risk of colorectal polyps in African Americans.

Dietary folate status appears to influence risk for colorectal cancer possibly by alterations in DNA methylation and nucleotide precursor pools. Polymorphisms (677C-->T and 1298A-->C) in methylenetetrahydrofolate reductase (MTHFR), a key enzyme in folate metabolism, determines enzyme activity. The frequency of polymorphisms in the gene varies extensively in different populations. We sought to determine the association between folate status, folate metabolism, DNA methylation, tobacco, alcohol consumption, and the risk of colorectal adenomas in African Americans. Among 58 patients who underwent a clinically indicated colonoscopy, 23 patients with histology confirmed colorectal polyps and 35 patients without were recruited for a case-control study. Blood samples were collected from fasting patients for determination of serum and red blood cell (RBC) folate, homocysteine, vitamin B(12), and methylation status. Polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) technique was performed to identify the MTHFR 677 C-->T polymorphism and specific PCR was used to analyze adenomatous polyposis coli (APC) gene-promoter sequence methylation. Among 23 cases, 49 polyps (adenomatous, n = 41 and hyperplastic, n= 8) were identified. Twenty-eight (57%) of the polyps were on the left side and 21 (42%) were on the right side of the colon. There was no association between the presence of colon polyps and levels of folate (serum, RBC), vitamin B(12), or homocysteine. Forty-eight individuals (84%) were homozygous for 677 CC. Of these individuals, 18 (37.5%) had >/=1 colorectal polyps, whereas 30 (62.5%) had no polyps. Nine individuals were heterozygous for 677 CT, and 4 (44%) of these individuals had colon polyps. Eighty-eight percent of the APC gene-promoter sequences tested using peripheral blood DNA from patients were unmethylated. Among the individuals who showed APC methylation, 66% had polyps; 33% were polyp free using their blood DNA. There was highly significant association between smoking and alcohol consumption with the presence of a colon polyp (P= .0006 and P= .05, respectively). In conclusion, the lack of the 677 TT may be a significant risk factor for colon neoplasm in the African-American population. Smoking and alcohol consumption were found to be risk factors for colon polyps. APC gene-promoter sequence methylation found in peripheral blood may be an indicator of risk for polyp formation and an important screening tool.

Acid rain effects on aluminum mobilization clarified by inclusion of strong organic acids.

Assessments of acidic deposition effects on aquatic ecosystems have often been hindered by complications from naturally occurring organic acidity. Measurements of pH and ANCG, the most commonly used indicators of chemical effects, can be substantially influenced by the presence of organic acids. Relationships between pH and inorganic Al, which is toxic to many forms of aquatic biota, are also altered by organic acids. However, when inorganic Al concentrations are plotted against ANC (the sum of Ca2+, Mg2+, Na+, and K+, minus S042-, N03-, and Cl-), a distinct threshold for Al mobilization becomes apparent. If the concentration of strong organic anions is included as a negative component of ANC, the threshold occurs at an ANC value of approximately zero, the value expected from theoretical charge balance constraints. This adjusted ANC is termed the base-cation surplus. The threshold relationship between the base-cation surplus and Al was shown with data from approximately 200 streams in the Adirondack region of New York, during periods with low and high dissolved organic carbon concentrations, and for an additional stream from the Catskill region of New York. These results indicate that (1) strong organic anions can contribute to the mobilization of inorganic Al in combination with SO42- and N03-, and (2) the presence of inorganic Al in surface waters is an unambiguous indication of acidic deposition effects.

Cropping systems for phytoremediation of phosphorus-enriched soils.

Eutrophication of freshwater bodies is frequently attributed to elevated phosphorus (P) concentrations in surface runoff from P-enriched agricultural soils. Forage and grain-cropping systems were compared for their effectiveness at remediating P-enriched soils. At each of four locations, one of three forage systems (Forage I = cereal rye silage and corn silage annually; Forage II = alfalfa; Forage III = annual ryegrass and corn silage annually) and the grain system (corn, small grain, and soybean rotation) were maintained for 3 yr on soils with five distinct initial soil P concentrations that were established by using four annual applications (1994-1997) of five different rates (0, 100, 200, 300, and 400 kg total P ha(-1) y(-1)) of poultry manure, dairy manure, or commercial fertilizer. Across all manure P treatments at all locations, the forage systems had greater removal of P than the grain system. Soil P concentration changes (2001-2004) did not reflect differences in crop P removal. Few significant reductions in soil P concentration were observed for either crop system. When reductions did occur, they were for the more highly enriched soil P treatments. No significant reductions in soil P concentration have occurred for the lowest manure P treatments. Considerable variability in crop P concentrations was observed among species at locations and among years produced. However, crop P concentrations did increase uniformly as soil P concentration increased, indicating that luxury consumption of P does occur in agronomic species produced on P-enriched soils.

Reactivation of Bentgrass Dead Spot and Growth, Pseudothecia Production, and Ascospore Germination of Ophiosphaerella agrostis.

Ophiosphaerella agrostis incites bentgrass dead spot (BDS) of creeping bentgrass. Little is known about the biology of O. agrostis; hence the primary goal of this study was to determine some basic biological properties of the pathogen and epidemiological components of the disease. Winter-dormant creeping bentgrass field samples showing symptoms of BDS were incubated at temperatures ranging from 15 to 30°C. Between 12 and 28 days of incubation, reactivation of BDS symptoms occurred at temperatures ≥20°C, but the greatest expansion in BDS patch diameter occurred at 25 and 30°C. The optimum temperatures for growth of hyphae among 10 O. agrostis isolates ranged from 25 to 30°C, and growth was suppressed at 35°C. Pseudothecia of O. agrostis were produced in vitro on a mixture of tall fescue seed and wheat bran. Pseudothecia developed under constant fluorescent light at 13 to 28°C, but no pseudothecia developed in darkness at any temperature. Pseudothecia developed in as few as 4 days, but the highest numbers appeared about 30 days after incubation began. Ascospores incubated at 25°C germinated in as little as 2 h, with germ tubes generally emerging from the terminal rather than interior cells of ascospores. Germination during the first 4 h of incubation was enhanced by both light and the presence of bentgrass leaves or roots. After 18 h of incubation, however, there were few differences in the percentage of ascospores germinated regardless of light treatment or presence of plant tissue.

RESEARCH: Are Recent Watershed Disturbances Associated with Temporal and Spatial Changes in Water Quality of Lake George, New York, USA?

/ Lake George, a mesooligotrophic lake, is a historically important recreational site in northeastern New York, USA. A preliminary analysis of the data, collected during 1980-1990, suggested that the indicators of primary productivity have increased, particularly in the southern basin of the lake. This change was attributed to the recent increases in the urbanization and development of the southern shorelines. The suggestion of temporal and spatial degradation in lakewater quality has caused substantial concerns among the decision makers and the public alike. The main objective of this study is to evaluate possible eutrophication of the lake by quantification of temporal and spatial trends in concentrations of total phosphorus (TP), chlorophyll a (Chl a), silica (Si), and chloride (Cl) through the use of proper statistical techniques. Results indicate no statistically significant changes in the concentrations of TP, Chl a, or Si in the spring or summer from 1981 to 1993. A significant temporal trend of increase in Cl concentration is, however, detected. This is perhaps the strongest evidence that the development of the Lake George watershed has affected lakewater chemistry. In spring, the concentrations of TP, Chl a, Si, and Cl, averaged over all 13 years, were higher in the south basin, but differences are not statistically significant (i.e., P > 0.05). In summer, Si was slightly but significantly lower, and Cl was nonsignificantly higher in the south basin. Significant interactions between temporal and spatial changes are detected based only on summer values of TP and Chl a, indicating differential trends of change for these two variables in the south and north basins during the last 13 years.KEY WORDS: Repeated-measures ANOVA; Split-plot design; Lakewater chemistry; Lake George

Seasonal variation of gas exchange and pigmentation in branches of three grafted clones of mature ponderosa pine exposed to ozone and acid rain.

Gas exchange and pigmentation responses of mature ponderosa pine (Pinus ponderosa Laws.) branches to ozone and acid rain exposure were investigated using three grafted clones growing in a managed seed orchard. Exposure of one-year-old foliage to twice ambient ozone (2 x AMB) resulted in significant decreases in net photosynthesis (Pn), stomatal conductance (gsw) and pigmentation relative to charcoal-filtered (CF) and ambient (AMB) ozone treatments. Ozone effects on gas exchange and pigmentation were most pronounced during late-season and differed significantly among clones. Environmental parameters (e.g. light, vapor pressure deficit, and temperature) accounted for more variation in Pn than did cumulative ozone exposure. Minimal differences in gsw and Pn among ozone treatments occurred during seasonal periods of high temperature and evaporative demand. Negative effects of 2 x AMB ozone on gsw and pigmentation were greatest for the clones having highest and lowest phenotypic vigor under ambient conditions; the clone of moderate phenotypic vigor under ambient conditions was least sensitive to ozone. Application of simulated acid rain of pH 3.0, pH 5.1 or no rain (NR) had little impact on gas exchange or pigmentation.

Effects of simulated acid rain and ozone on foliar chemistry of field-grown Pinus ponderosa seedlings and mature trees.

We investigated the additive and interactive effects of simulated acid rain and elevated ozone on C and N contents, and the C:N ratio of one-year-old and current-year foliage of field-grown mature trees and their half-sib seedlings of a stress tolerant genotype of ponderosa pine. Acid rain levels (pH 5.1 and 3.0) were applied weekly to foliage only (no soil acidification or N addition), from January to April, 1992. Plants were exposed to two ozone levels (ambient and twice-ambient) during the day from September 1991 to November 1992. The sequential application of acid rain and elevated ozone mimicked the natural conditions. Twice-ambient ozone significantly decreased foliar N content (by 12-14%) and increased the C:N ratio of both one-year-old and current-year foliage of seedlings. Although similar ozone effects were also observed on one-year-old foliage of mature trees, the only statistically significant effect was an increased C:N ratio when twice-ambient ozone combined with pH 3.0 rain (acid rain by ozone interaction). Enhancing the effect of twice-ambient ozone in increasing the C:N ratio of one-year-old foliage of mature trees in June was the only significant effect of acid rain.