Soil invertebrate and plant responses to mowing and carbofuran application in a North American tallgrass prairie

Relationships between soil invertebrate populations and primary production of a tallgrass prairie were investigated using the insecticide-nematicide carbofuran and a range of mowing intensities to manipulate invertebrate densities and resource quantity and quality. The trophic composition of nematode populations was monitored through each of two growing seasons. Earthworm and macroarthropod densities and primary production were assessed at the end of the second season. Invertebrate densities were generally reduced in carbofuran-treated plots, although individual weights of surviving macroarth-ropod herbivores increased significantly (p<0.05). Carbofuran failed to affect estimates of above- or belowground plant biomass after two years of treatment. Changes in resource quantity and quality resulted in rapid responses by dominant invertebrate consumer populations. A 28% reduction in live root mass and a 24% increase in root detritus following two years of mowing was associated with a 54% decrease in herbivorous nematode densities, a 47% increase in microbivorous nematode densities, and a 41% increase in native earthworm biomass.     

Role of alternative pathway respiration in tomato roots attacked by Meloidogyne incognita

The effect of nematode infestation on the alternative pathway respiration of mitochondria isolated from resistant and susceptible tomato roots greatly depended on the oxidisable substrate tested. The percentage of alternative respiration in NADH, malate and succinate oxidation was markedly different between the resistant (Rossol) and the susceptible (Roma VF) cultivars before infestation. Only the percentage of malate alternative oxidation in mitochondria from the resistant roots was influenced by nematode invasion. Conversely, attacked roots showed consistent variations in the content of mitochondria per unit fresh weight and in the phosphorylation efficiency (ADP/O) of the organelles. Expression of the alternative pathway (ρ' value) was found to be unchanged in intact roots and isolated mitochondria six days after nematode inoculation.     

Marine ecosystem dynamics: Comparison of scales

When marine and terrestrial ecological systems are compared at the same time scales, there are very great differences in their relations with their physical environments. Similarities arise when comparisons are made at different time scales. There are significant consequences for management.     

Biocontrol of the apple sawfly,Hoplocampa testudinea,with entomogenous nematodes

Four types of experiments were conducted to assess the pathogenicity of entomogenous nematodes against the apple sawfly,Hoplocampa testudinea Klug (Hymenoptera: Tenthredinidae). In Petri dish,Steinernema carpocapsae (Weiser) DD 136 strain,S. carpocapsae All strain,S. feltiae (Filipjev) andHeterorhabditis bacteriophora Poinar caused 100% larval mortality 72 h after the treatments. In semi-field conditions under dwarf apple trees, a single treatment with either 40 or 80S. carpocapsae All strain/cm² caused significant (>80%) larval mortality. No significant increase in mortality was obtained with a second application. In 1990, late treatment with 80S. carpocapsae All strain/cm² caused significant (39.1%) pupal mortality. In 50×50 cm quadrats under dwarf apple trees, treatment with 40 and 80S. carpocapsae All strain/cm² were done in spring 1989. In spring 1990, respectively 22 and 25 apple sawfly adults emerged from quadrats treated with 40 and 80S. carpocapsae All strain/cm², whereas 78 adults emerged from untreated quadrats. In a foliar application experiment, a single treatment withS. carpocapsae All strain significantly reduced the percent of fruit showing secondary damage. The possibility of using entomogenous nematodes as part of an integrated pest management in apple orchards is discussed, with particular reference to the integration of programs aimed at managing plum curculio,Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) populations.      

Infection of the Cat Flea, Ctenocephalides felis (Bouché) by Neoaplectana carpocapsae Weiser

Infection of cat flea, Ctenocephalides felis, larvae by the entomophilic nematode Neoaplectana carpocapsae was accomplished in the laboratory. The Breton strain of N. carpocapsae provided higher larval mortality at lower dosages than did the DD-136 strain. Adult nematodes were evident in the insect hemocoel after 48 h; however, no infective third-stage larvae were produced. Larval flea infection increased with an increase in the moisture content of sand from 2% to 7% and of sandy clay from 7% to 12%. Larval flea infection was also obtained on turf containing dauer larvae. Nematode penetration of cocoons with invasion of prepupal and pupal fleas was apparent.     

Nematode Temperature Responses: a Niche Dimension In Populations of Bacterial-Feeding Nematodes

The optimum temperatures for population development were determined for six species of bacterial-feeding nematodes from among eight temperatures, ranging from 5 to 40 C. Four of the species are cohabiting species. The range of temperatures over which population development occurs (temperature niche breadth) is different for the cohabiting species. This difference may be a means of reducing competition between species, thus increasing temperatures over which habitats can be exploited.     

Nematicidal Principles from Two Species of Lamiaceae

Aqueous extracts of Ocimum sanctum and O. basilicum leaves contained compounds that killed Meloidogyne incognita larvae in 160 min. Thin layer and gas-liquid chromatography, and infrared spectrophotometry indicated that the essential oils eugenol and linalool were the active nematicidal compounds.     

Mineral salt requirements of Bacillus globisporus subsp. marinus strains

The mineral salt requirements of four isolates of Bacillus globisporus subsp. marinus and of two terrestrial strains of B. globisporus were investigated. In contrast to the terrestrial reference strains the marine isolates showed an obligate requirement for sodium and potassium. The sodium ion could not be replaced by potassium or by osmotically equivalent concentrations of mannitol. None of the strains proved to be dependent upon Mg²⁺ or Ca²⁺. The B. globisporus subsp. marinus strains are considered true marine bacteria. The criteria used to distinguish between marine and terrestrial Gram-negative bacteria can also be applied for Gram-positive bacteria.     

Endogenous respiration and regulation in a primitive marine fungus

The relationship between the respiration and the presence and utilization of endogenous and exogenous substrates was studied in the non-filamentous obligately marine fungus Thraustochytrium aureum. Using isotopic and manometric methods, it was shown that almost all exogenous glucose is assimilated, whilst almost all the oxygen consumption in the presence of exogenous glucose was due to oxidation of endogenous reserves. In contrast, exogenous glutamate, which cannot serve as the sole carbon source for growth, inhibits respiration of endogenous materials, and is itself rapidly oxidized. The uncoupler 2,4-dinitrophenol stimulates the oxidation of endogenous reserves without affecting the uptake and use of exogenous glucose. These data strongly support the idea of physiologic compartmentation in this organism.     

Sequestration of arginine by polyphosphate in vacuoles of yeast (Saccharomyces cerevisiae)

The conditions for synthesis, purification, and properties of tryptophanase by a marine organism (Vibrio K-7) were studied. Tryptophanase was induced by tryptophan and its analogs, and partially repressed by 0.5% glucose or glycerol. NaCl (0.4M) was required for optimal growth and tryptophanase activity in whole cells. The enzyme was purified to 92% homogeneity by heat treatment, hydroxyapatite chromatography and fractionation with ammonium sulfate. This tryptophanase has been found to have kinetic properties similar to the tryptophanase from other microorganisms. It carries out both , -elimination reactions (using tryptophan, serine, cysteine and S-methyl-cysteine as substrates) and -replacement reactions (forming tryptophan from indole and serine, cysteine or S-methyl-cysteine). The enzyme has a sedimentation coefficient of 9.2S and requires pyridoxal 5-phosphate as a cofactor. The optimal pH for the tryptophanase reaction is pH 8.0.Nonstandard Abbreviations PLP pyridoxal 5-phosphate - TPase tryptophanase - TSase tryptophan synthase - DHase dehydratase - TCA tricarboxylic acid - BSA bovine serum albumin Preliminary reports of this work have been presented (M. J. Klug and R. D. DeMoss, Bacteriol. Proc. 1971, p. 132; D. D. Whitt and R. D. DeMoss, Abstr. Annu. Meet. Am. Soc. Microbiol. 1973, p. 148)