Application of the most probable number method to estimations of entomopathogenic nematode populations in soil

The calculation of most probable numbers (mpn) was used for the estimation of numbers of infective entomopathogenic nematodes in soil. The mpn concept was first introduced in bacteriology as a means of estimating numbers of organisms in a substrate without a direct count, in cases where direct enumeration could not be applied. In the work reported here, soil samples infested with infective juveniles (IJs) of Heterorhabditis megidis (isolate HF85) were diluted with uninfested soil and the diluted soils were baited with mealworm larvae (Tenebrio molitor). The mpn of infective units of IJs in the undiluted soil was calculated. The mpn calculation was found to be applicable to entomopathogenic nematodes in soil under particular conditions. It could be successfully applied to data for the response of soil units but not to the data based on the response of individual insects, as the latter did not confirm to a Poisson series. The calculated mpn represented between 2.9 and 7.1% of the initial inoculum of IJs. It was suggested that IJs might act as a group in infecting an insect host. Using the data for Tenebrio mortality on parasitisation, the mpn based on quantal response of the mealworms would therefore not give the true density of IJs in the soil sample but the effective density, or the quantity of infective units. Although the biological significance of the infective unit needs further clarification, mpn was found to be a useful parameter for use in comparative experiments.     

The Relativistic Quantum Defect Orbital Method and some of its Applications

Justification of a simple and reliable relativistic procedure for the prediction of a large body of transition probability data is made. The main features of the Relativistic Quantum Defect Orbital (RQDO) formalism are described, and several examples of the data yielded by this method are presented in tabular and graph forms.     

Quantification of Endospore Concentrations of Pasteuria penetrans in Tomato Root Material

Six methods for quantification of the endospore concentrations of Pasteuria penetrans from tomato roots are described. Mortar disruption and machine disruption methods gave the highest estimations (endospores per gram of root material) of 83.7 and 79.0 million, respectively. These methods were significantly superior to incubation bioassay (47.7 million), enzymatic disruption (32.1 million), and enzymatic disruption + flotation (25.8 million) methods. A centrifugation bioassay method gave the lowest estimation of 12.7 million.     

On partial local smoothing rules for curve estimation

We compare the performances of local and global rules for smoothingparameter choice, in terms of asymptotic mean squared errorsof the resulting estimators. In some instances there is surprisinglylittle to choose between local and global approaches; our analysisidentifies contexts where the differences are small or large.This work motivates development of smoothing rules that forma ‘half-way house’ between local and global smoothing.There, interpolation provides a basis for partial local smoothing.A key result shows that interpolation on even a coarse gridcan produce a very good approximation to full local smoothing.Our theoretical and numerical results lead us to suggest linearinterpolation of a bandwidth obtained by integral approximationson discrete intervals.     

Multi-mesh gillnets to estimate species composition and catch per unit effort of fish in a small water body in Zambia

A standard method comprising multi-mesh monofilament nylon gillnets and depth stratification, the Drottningholm method, was employed in test fishing of a small Zambian reservoir (32 ha) on eight occasions over 1 year. The catch per unit effort (cpue) from the 0–3 and 3–6 m zone was timated with benthic and pelagic nets, while in the 6–12 m zone only benthic nets were used. Results include species caught and cpue with coefficients of variation and confidence intervals, for net types and depth zones. A total of 11 species were caught, of which Burbus paludinosus , B. marequensis , Laheo cylindricus , and Oreochromis sp. dominated. Coefficients of variation did not indicate a preferable season for test fishing. During the cold season some species were not caught. The applicability of the method in estimation of species composition and cpue is discussed.     

Estimating Arundo donax shoot biomass

We developed an equation for estimating Arundo donax shoot dry weight from shoot length. The equation, shoot dry weight (g) = 14.254 (standard error = ±0.275) × shoot height² (m), was as effective at explaining a high proportion of total variation in shoot dry weight (R² = 0.90) as more complicated equations containing additional morphometric parameters. Tested against two independent datasets, the equation provided accurate estimates of dry weight for shoots ranging from 0.3 to 7.06 m height (dataset 1, P < 0.0001, R² = 0.87, N = 29; dataset 2, P < 0.0001, R² = 0.82, N = 192). The equation provides aboveground biomass estimates from stem counts and heights more rapidly than harvest methods.