Lead in albacore: guide to lead pollution in Americans.

Lead contamination in canned tuna, exceeding natural concentrations 10,000-fold, went undiscovered for decades because of analytical error. The magnitude of this pollution effect helps explain the difference between the lead concentration in the diets of present-day Americans (0.2 part per million) and inthe diets of prehistoric peoples (estimated to be less than 0.002 part per million). It also explains how skeletal concentrations of lead in typical Americans became elevated 500-fold above the natural concentrations measured in bones of Peruvians who lived in an unpolluted environment 1800 years ago. It has been tacitly assumed that natural biochemical effects of lead in human cells have been studied, but this is not so because reagents, nutrients, and controls used in laboratory and field studies have been unknowingly contaminated with lead far in excess of naturally occurring levels. An unrecognized form of poisoning caused by this escessive exposure to lead may affect most Americans because magnitudes of biochemical dysfunctions are proportional to degrees of exposure.

Quantifying the Effects of Lance Nematode Parasitism in Creeping Bentgrass.

We compared photosynthesis and multispectral radiometry (MSR) measurements with visual quality ratings for assessment of feeding injury to creeping bentgrass caused by the lance nematode (Hoplolaimus galeatus) using artificially infested microplots and a naturally infested putting green. Nematode feeding resulted in negative visual and MSR effects on creeping bentgrass in microplots. Visual quality ratings were correlated more consistently with nematode densities than either individual MSR variables or factor models of MSR variables. Threshold estimates for H. galeatus population densities associated with unacceptable bentgrass quality in microplots varied widely by month and year. Similarly, the relationship between H. galeatus population density and turf health indicators (including MSR measurements, visual ratings, and net photosynthetic rate) varied with cultivar and management practice (irrigation frequency and mowing height) in the naturally infested putting green. Notably, negative effects of nematode feeding were not consistently associated with more stressful management practices, suggesting that stress avoidance is not a reliable deterrent to H. galeatus damage in creeping bentgrass. Damage thresholds for this nematode-host association are dynamic and should be used with caution.

Population Dynamics of the Lance Nematode (Hoplolaimus galeatus) in Creeping Bentgrass.

The effects of management practices and nematode population density on the seasonal fluctuationsin lance nematode (Hoplolaimus galeatus) populations in creeping bentgrass were studiedin a naturally infested experimental putting green and in artificially infested microplots. In general, H. galeatus populations increased from late spring through midsummer, declined in August, and increased again in the fall. Population increase in microplots was strongly density dependent, with final population densities inversely proportional to inoculum levels. Ectoparasitic populationsof H. galeatus in both studies were composed of adults and juveniles, whereas endoparasiticpopulations were almost exclusively juveniles. H. galeatus populations in the naturallyinfested site were aggregated spatially, but the aggregation was not temporally stable. Nematodepopulations were not affected by bentgrass cultivar selection or irrigation frequency.

Development of Brown Patch and Pythium Blight in Tall Fescue as Affected by Irrigation Frequency, Clipping Removal, and Fungicide Application.

We studied the effects of irrigation frequency, clipping removal, and fungicide application on the development of Rhizoctonia brown patch (Rhizoctonia solani) and Pythium blight (Pythium aphanidermatum) in tall fescue. Brown patch severity was not significantly different between plots irrigated daily and those irrigated on alternate days. Similarly, no differences in brown patch were observed in plots where grass clippings were returned to the sward with a mulching mower compared with plots where clippings were removed. Preventive applications of azox-ystrobin at 35-day intervals or postinfection applications of chlorothalonil reduced brown patch severity, but only the azoxystrobin treatment provided aesthetically acceptable (<10%) levels of brown patch control. However, azoxystrobin applications also increased Pythium blight compared with untreated or chlorothalonil-treated tall fescue, especially in plots that received daily irrigation.