Evaporation of Ice in Space: Saturn's Rings

The photosputtering erosion velocity of ice in space is estimated to be 400 centimeters per billion years at 1 astronomical unit.     

Interrelations between nitrogen and phosphorus fertilization and early blight control of potatoes

Three different rates of soil-applied nitrogen were combined in all possible combinations with different schedules of fungicidal sprays for early blight (Alternaria solani) control in field experiments for three consecutive years. The nitrogen was applied with a constant rate of phosphorus. Yield response to fungicidal sprays was more pronounced when potato plants had received nitrogen and phosphorus. Both spraying and fertilizer application reduced the percentage of leaflets infected by early blight. However, the effect of the fungicide was greater than that of fertilizers. Estimates based on the cost and price assumptions indicated that $1.00 investment in the optimum number of fungicidal sprays at the adequate rate of fertilizer returned $8.34, $9.71 and $1.89 in 1970, 1971 and 1972, respectively.     

Enhanced efficiency of electrostatically charged insecticide aerosols

The bioefficacy of a standard domestic aerosol insecticide has been compared with that of a similar spray in which the droplets were electrostatically charged. The aerosol was charged without the need for an external power supply, by enhancing natural charge separation processes that occur during atomisation. The charge-to-mass ratio achieved was 1.1 x 10(-4) C kg-1, compared with 2.2 x 10(-5) C kg-1 for the standard aerosol. Efficiency was assessed for insects in free flight. A direct space-spray application method was used to study the bioefficacy of these aerosols on houseflies, Musca domestica, and an indirect space-spray method on houseflies and mosquitoes, Culex quinquefasciatus. Two levels of concentration of active ingredients were compared. At low concentrations of 1.57 g kg-1 of bioallethrin and 0.29 g kg-1 of bioresmethrin, the charged aerosol achieved a significant reduction in KDT50 (time at which 50% of the flies were knocked down), compared with the standard aerosol. In the direct spray application to houseflies, the KDT50 was reduced by 50%, while in the indirect spray the KDT50 was reduced by 40%. In the indirect spray of mosquitoes, the KDT50 was reduced by 22%. With higher active ingredient concentrations of 2.09 g kg-1 for bioallethrin and 0.39 g kg-1 for bioresmethrin, the charged aerosol also demonstrated faster knockdown than the standard, but the improvement was less marked. In the direct spray application to houseflies, the KDT50 was reduced by 21% compared with the standard aerosol, while in the indirect spray the KDT50 was reduced by 16%. In the indirect spray of mosquitoes, the KDT50 was reduced by 24%. The percentage mortality after 24 h was also increased with the charged aerosol. Charge carried by the droplets results in increased interception of the insecticide, as the droplets are attracted to the insects in flight and space charge effects within the aerosol could cause improved dispersion in the test chamber.     

Cherry picking by pseudomonads: After a century of research on canker,genomics provides insights into the evolution of pathogenicity towards stone fruits

Bacterial canker disease is a major limiting factor in the growing of cherry and other Prunus species worldwide. At least five distinct clades within the bacterial species complex Pseudomonas syringae are known to be causal agents of the disease. The different pathogens commonly coexist in the field. Reducing canker is a challenging prospect as the efficacy of chemical controls and host resistance may vary against each of the diverse clades involved. Genomic analysis has revealed that the pathogens use a variable repertoire of virulence factors to cause the disease. Significantly, strains of P. syringae pv. syringae possess more genes for toxin biosynthesis and fewer encoding type III effector proteins. There is also a shared pool of key effector genes present on mobile elements such as plasmids and prophages that may have roles in virulence. By contrast, there is evidence that absence or truncation of certain effector genes, such as hopAB, is characteristic of cherry pathogens. Here we highlight how recent research, underpinned by the earlier epidemiological studies, is allowing significant progress in our understanding of the canker pathogens. This fundamental knowledge, combined with emerging insights into host genetics, provides the groundwork for development of precise control measures and informed approaches to breed for disease resistance.     

Serum antibody levels to Taenia saginata in cattle grazed on Scottish pastures

The serum antibody levels to Taenia saginata of three groups of cattle were assessed by an enzyme-linked immunosorbent assay (ELISA). The first group of cattle were from four farms which had a confirmed T saginata cysticercosis outbreak, all of which had cattle classed as infected by ELISA. The second group were from four farms where sewage sludge had been applied to pasture subsequently grazed by the cattle. One of these farms had cattle classed as infected by ELISA. The control cattle, which were all classed as uninfected by ELISA, came from five farms whose pasture had not been treated with sewage sludge. In a wider survey, involving sera from 47 additional farms, the majority could not be distinguished from the control farms in the earlier survey. However, samples from three of the farms had a similar number of positives to two of the known infected farms in the initial survey. Since the ELISA assay may indicate infected herds, farms such as these warrant further investigation.     

Molecular identification of Echinococcus granulosus genotypes (G1 and G7) isolated from pigs in Mexico

With the aim of genotyping Echinococcus granulosus cysts found in Mexican livestock, we collected hydatid cysts from the livers and lungs of pigs in slaughterhouses in the state of Morelos, Central Region of Mexico. DNA was extracted from the parasites and examined by polymerase chain reaction (PCR) of rDNA internal transcribed spacer 1 (ITS1-PCR), Eg9-PCR, Eg16-PCR, and PCR-restriction fragment length polymorphism (PCR-RFLP). In addition, fragments of the genes coding for mitochondrial cytochrome c oxidase subunit 1 (CO1) and NADH dehydrogenase 1 (ND1) were sequenced. Two different genotypes of E. granulosus were unequivocally identified, the common sheep genotype, G1, and the common pig genotype, G7. The G1 genotype of E. granulosus has not been previously demonstrated in Mexico. Because of its recognized infectivity in humans, G1 genotype is a direct threat to human health and its presence in Mexico is consequently of immediate public health importance and epidemiological relevance.     

The effect of temperature and other factors on chlorophyll a fluorescence and the lower oxygen limit in apples (Malus domestica)

The effects of temperature, scan interval and rate of oxygen (O₂) decline on pulse frequency modulation (PFM)-based minimum fluorescence (F_α) and the F_α-based lower oxygen limit (LOL) were investigated using ‘Honeycrisp’ apples (Malus × domestica Borkh). The effects of temperature and hypoxic stress on pulse amplitude modulation (PAM) fluorescence parameters were also investigated. The PFM scan interval had no effect on the F_α baseline, but increases in the scan interval decreased the low-O₂-induced fluorescence spike intensity (ΔF_α). Temperature negatively correlated with the F_α baseline while ΔF_α °C⁻¹ was greater at lower than at higher temperatures. When using a PAM fluorometer, the minimum fluorescence (F_o), and to a lesser extent the maximum fluorescence (F_m), were similarly affected by temperature as was F_α. Temperature altered the LOL in fruit. Apples stored at 20, 10, 3.5 and 0 °C spiked at 0.72, 0.33, 0.22 and 0.08 kPa O₂, respectively, under a rapid O₂ decline (i.e., 20.9 to <1 kPa O₂ in ≈5–6 h). Although the low-O₂ F_α spike apex values did not change with temperature, the spike intensity increased with temperature due to a reduced fluorescence baseline. A slower O₂ decline rate produced slightly higher LOL and lower spike intensity values. In conclusion, temperature and rate of O₂ decline affected the low-O₂-induced PFM fluorescence spike intensity as well as the LOL, while the PFM scan interval affected the spike intensity.