Inactivation of Paecilomyces fumosoroseus conidia by diffuse and total solar radiation

Abstract: The detrimental photic effects of natural solar radiation on the conidial persistence of the entomopathogenic hyphomycete Paecilomyces fumosoroseus were investigated by exposing quiescent conidia either to total solar radiation or to its diffuse component. A given amount of UVB diffuse radiation was found to be as detrimental, and sometimes twice as detrimental, as the same amount of total solar radiation. The variability in quantity and spectral distribution of the diffuse component of UVB solar radiation reaching the earth's surface, observed through spectral measurements, may be responsible for the difference in biological effects.     

Comparison of the Efficacy of Entomopathogenic Nematodes for the Biological Control of the Mushroom Pests Lycoriella auripila (Sciaridae) and Megaselia halterata (Phoridae)

The efficacy of different species of entomopathogenic nematodes was tested against larvae of the mushroom phorid Megaselia halterata (Diptera: Phoridae) and the mushroom sciarid Lycoriella auripila (Diptera: Sciaridae). Sciarid larvae originating from infestations in casing soil during colonization by Agaricus bisporus were almost completely controlled by applications of Steinernema feltiae to the casing soil. When larvae originated from infestations in freshly spawned compost, they could be controlled by compost applications halfway through spawnrunning and by very early casing treatments. The control of phorids in compost was maximally 31% when nematodes were mixed within the infested compost at a concentration of 3 106 nematodes/m2. Only slightly higher reduction rates were obtained at higher concentrations. The control of phorids was more promising in the infested casing layer, in which S. carpocapsae was most successful. At concentrations of 6 and 15 106 nematodes/m2 this species obtained reduction rates of 65 and 73% respectively when it was applied 3 days after the end of the infestation period. These concentrations are, however, too high for practical application.     

Effect of microclimate heterogeneity and ventilation system on entomopathogenic hyphomycete infection of Trialeurodes vaporariorum (Homoptera: Aleyrodidae) in Mediterranean greenhouse tomato

Collaborative research was conducted in the south of France to assess constraints related to both climate heterogeneity and ventilation systems on the control potential of a Lecanicillium muscarium-based formulation against whiteflies in Mediterranean greenhouses. Four series of small-scale greenhouse trials were performed in 2001 and 2002. Two applications at 4–5 day intervals of Mycotal were conducted on young larvae of the greenhouse whitefly, Trialeurodes vaporariorum, at the rate recommended by the manufacturer (ca. 10¹⁰ viable spores per liter of water suspension). The climatic heterogeneity was taken into account by comparing the fungus-induced mortality of nymphs located on lateral row plants to that of nymphs on center row plants. In spite of significant differences in air flows (0.7–1.2 and 0.3 ms⁻¹, respectively) there was no effect on fungus efficacy (53–76% mortality). When comparing the influence of greenhouse equipment (sophisticated glasshouse vs. polyethylene-covered greenhouse), the fungus was not affected (89–96% mortality) in spite of significant differences in ventilation rates. The results confirmed that entomopathogenic Hyphomycetes have a strong potential for microbial control of whitefly larvae infesting tomato crops at moderate ambient humidity in Mediterranean greenhouses in spite of windy periods. These investigations confirmed that microclimatic conditions prevailing in the targeted insect habitat (under-leaf surface boundary layer) are greatly disconnected from that of both outside and inside the greenhouse. In northern Mediterranean greenhouses, non-stressed tomato crops provide unexpected favorable conditions for mycoinsecticide use against a phyllophagous insect.     

Chronic intravenous infusion of noradrenaline produces labile hypertension in conscious rats

Nonadrenaline was infused intravenously for 5 days into conscious, unrestrained normotensive rats. Infusion of 40 μg per kg body weight per hour caused a chronic elevation of blood pressure, reaching a maximum increase of 28 ± 5 mm Hg on the fifth day. This hypertension is characterized by a labile blood pressure: periods of normotension are followed by rapid outbursts of hypertension. Resting plasma levels of noradrenaline ranged from 0.20–1.25 ng/ml. Infusion of 40 μg per kg body weight per hour caused a 4–5 fold increase. These observations suggest that chronic elevations of plasma noradrenaline are associated with labile hypertension.     

Tree Species Effects on Calcium Cycling: The Role of Calcium Uptake in Deep Soils

Soil acidity and calcium (Ca) availability in the surface soil differ substantially beneath sugar maple (Acer saccharum) and eastern hemlock (Tsuga canadensis) trees in a mixed forest in northwestern Connecticut. We determined the effect of pumping of Ca from deep soil (rooting zone below 20-cm mineral soil) to explain the higher available Ca content in the surface soil beneath sugar maple. We measured the atmospheric input of Ca with bulk deposition collectors and estimated Ca weathering and Ca mineralization in the surface soil (rooting zone above 20-cm mineral soil) from strontium isotope measurements and observed changes in exchangeable Ca in soils during field incubation. Calcium leaching at 20 cm was calculated by combining modeled hydrology with measured Ca soil solution concentrations at 20-cm depth. We measured root length distribution with depth beneath both tree species. Calcium leaching from the surface soil was much higher beneath sugar maple than hemlock and was positively related with the amount of Ca available in the surface soil. Calcium leaching from the surface soil beneath sugar maple was higher than the combined Ca input from atmospheric deposition and soil weathering. Without Ca uptake in the deep soil, surface soils are being depleted in Ca, especially beneath sugar maple. More organically bound Ca was mineralized beneath sugar maple than beneath hemlock. A relatively small part of this Ca release was leached below the surface soil, suggesting that, beneath both tree species, most of the Ca cycling is occurring in the surface soil. Sugar maple had more fine roots in the deep soil than hemlock and a greater potential to absorb Ca in the deep soil. With a simple model, we showed that a relatively small amount of Ca uptake in the deep soil beneath sugar maple is able to sustain high amounts of available Ca in the surface soil. Received 20 June 2001; accepted 6 December 2001.