Influence of Portland cement amendment on soil pH and residual soil termiticide performance

Soil adjacent to new brick veneer work is likely to have a higher pH owing to the mixture of cement with the soil. In the Gainesville, FL, area, soil samples taken from such locations had a range of pH values from 9.0 to 10.1; similar soils used in bioassays had a pH of 5.6 before the addition of cement. Addition of 15 mg of Portland cement to 33 g of soil increased the pH to 6, and addition of 291 mg of Portland cement increased the pH to 9. The pH of soil amended with cement was stable for the first 5 months. After 10 months, soil pH values decreased from alkaline to near neutral in all cases. Eastern subterranean termite workers, Reticulitermes flavipes (Kollar), were exposed to the treated soil at pH 6-9 for 24 h, and percentage mortality was recorded at 5 days, 5 months and 10 months. Termite mortality significantly decreased at higher soil pHs for bifenthrin, chlorpyrifos, fipronil and imidacloprid treatments at 5 months and similarly for bifenthrin, permethrin, chlorpyrifos, fipronil and imidacloprid treatments at 10 months. There was an inverse linear relationship between soil pH and mortality. Increased soil pH diminished residual activity of termiticide in the following order: imidacloprid > fipronil > chlorpyrifos = bifenthrin > permethrin > cypermethrin.     

Éléments de biologie chez Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae): 2 – Capacités de développement sur hôtes en conditions in vivo et in vitro

La présente étude, portant sur quatre populations sud-américaines de N. aberrans , s'est attachée à comprendre les capacités de multiplication de ce nématode en conditions in vitro (plante développée sur milieu gélosé) et en conditions in vivo (plante développée en pot). Le développement in vitro de N. aberrans est possible dans une gamme non exhaustive de température de 10°C à 25°C, avec un optimum à 20°C, sur de nombreuses plantes d'intérêt agronomique. Toutefois, cette capacité in vitro varie d'une population à une autre et est fortement conditionnée par la pénétration du nématode au stade J2 dans les racines. Les essais in vivo ont montré que la betterave et la tomate sont de très bons hôtes pour toutes les populations testées, alors que d'autres cultures sont favorables à certaines populations (pomme de terre et populations «race pomme de terre>>, poivron et populations «race betterave>>). Enfin, certaines plantes bien que ne présentant pas de symptômes de parasitisme (galles) sont capables d'héberger le nématode en lui permettant d'atteindre le stade J4 sans pour autant réaliser son cycle biologique en entier, ni se reproduire (haricot, concombre). Ces éléments biologiques soulignent le risque réel et majeur d'établissement pour la zone européenne de N. aberrans en cas d'introduction, nématode apte à se développer sur de nombreuses plantes, quel qu'en soit le mode de culture et parfois en l'absence de tout symptôme.     

Climatic Constraints to the Potential of Microsphaeropsis amaranthi as a Bioherbicide for Common Waterhemp

ABSTRACT The fungal plant pathogen Microsphaeropsis amaranthi is a candidate bioherbicide for the control of weedy Amaranthus species since it grows and sporulates readily in culture, is a pathogen of a number of important weed species, and is host-restricted to the family Amaranthaceae. This study was designed to determine the optimum and limiting environmental conditions for the efficacy of foliar applications of M. amaranthi for the control of common waterhemp. The greatest disease severity and the greatest plant biomass reductions were found when a prolonged leaf wetness period of >/= 12 h at 18 to 24 degrees C was provided after application. Disease severity and plant biomass reductions were greater when plants were treated at an earlier stage of development. Disease severity and impact were limited when shorter leaf wetness periods were provided, with negligible disease observed on plants provided with 相似文献   

Development of Stem-base Pathogens on Different Cultivars of Winter Wheat Determined by Quantitative PCR

The progress of development of stem-base pathogens in crops of second winter wheat was plotted in nine experiments in three years. The amount of each pathogen present was determined by quantitative PCR. Where Tapesia yallundae was present in quantifiable amounts, it usually developed earlier than the other eyespot pathogen, T. acuformis. Both species were usually present in greater amounts on cultivars which are more susceptible to eyespot. The sharp eyespot pathogen, Rhizoctonia cerealis, developed more erratically than either of the Tapesia spp. and there were no consistent effects on different cultivars. Fusarium spp., the cause of brown foot rot, were rarely present in quantifiable amounts, but Microdochium nivale was usually present as one or both of the varieties nivale and majus. Late-season (after anthesis) decreases in M. nivale suggest that any brown foot rot symptoms attributable to this fungus would have fully developed earlier. Cultivar differences in amounts of M. nivale were most clear in stems during internode extension and when relatively large amounts of DNA were present. Such differences approximately reflected eyespot susceptibility, cv. Soissons containing most and cv. Lynx containing least DNA. The results emphasise the difficulty in relating diagnoses, by quantitative PCR or other means, at early growth stages when decisions to apply fungicides against stem-base disease are made, to later disease severity.     

The significance of guttation in the secondary spread of Clavibacter michiganensis subsp. michiganensis in tomato greenhouses

Bacterial canker, caused by Clavibacter michiganensis subsp. michiganensis (Cmm), can spread in commercial tomato greenhouses causing epidemics. Results of greenhouse experiments with Cmm‐contaminated tools demonstrated disease spread for only a limited distance (<4 plants) from infected plants. However, touching symptomless infected plants bearing guttation droplets prior to touching nearby plants spread the pathogen over longer distances within rows (>22 plants). The pathogen was exuded in large numbers in the guttation fluid of infected plants; its presence in the guttation fluid was not influenced by the inoculation procedures, leaf age or the volume of the guttation droplets. Population size of Cmm and the incidence of leaflets with epiphytic bacteria were significantly higher in plants placed in a guttation‐induction chamber than in those kept in a growth chamber with high humidity, suggesting exudation through guttation contributed to the formation of epiphytic populations on leaflets. This new knowledge may provide a simple and environmentally friendly means for decreasing the spread of the disease by avoiding contact with plants during periods when they bear guttation droplets.     

Biological control of botrytis bunch rot in organic wine grapes with the yeast antagonist Candida sake CPA‐1

The aim of this research was to confirm the efficacy of the yeast antagonist Candida sake CPA‐1 in suppressing botrytis bunch rot development, in an organic vineyard under Mediterranean conditions for two seasons, and compare its performance with that of two biologically based products currently registered for botrytis bunch rot control in New Zealand. In 2009, treatments applied were: commercial formulations of Ulocladium oudemansii (BOTRY‐Zen^®) and chitosan (ARMOUR‐Zen^®), C. sake CPA‐1 combined with the fatty acid‐based additive Fungicover^® and combinations of these products. All treatments were applied six times between early flowering and harvest and compared with an unsprayed control. In 2010, the treatments focused on C. sake and Fungicover and the number of applications was reduced from six to four. The population dynamics of U. oudemansii and C. sake were measured and wine quality tests were carried out in both seasons. Disease control achieved by C. sake treatments in 2009 were comparable to those achieved by BOTRY‐Zen and ARMOUR‐Zen. Applications of C. sake plus Fungicover between flowering and harvest significantly (P < 0·05) reduced botrytis bunch rot incidence and severity by 64% and 90%, respectively, compared with the untreated control in 2009, and by 67% and 89%, respectively, in 2010. Treatments did not adversely affect wine quality parameters after treated grapes were processed. Candida sake consistently provided effective control of botrytis bunch rot in grapes under different meteorological and disease pressure conditions, thereby improving its potential for future commercial applications.     

Biochemical responses to ultraviolet‐C radiation and methyl jasmonate in Pinus radiata seedlings that accompany induced resistance to Diplodia pinea

Irradiation of Pinus radiata seedlings with ultraviolet‐C (UV‐C) radiation or spray application of methyl jasmonate (MeJA) each resulted in induced resistance to subsequent wound inoculation with Diplodia pinea. Induced resistance was expressed by lower incidence of disease and by reduced size of stem lesions than in untreated seedlings. UV‐C was more effective than MeJA and the induced resistance was greatest in seedlings that were irradiated with UV‐C for 60 min, 1 week before pathogen inoculation. Induced resistance in the UV‐C treated stems was concomitant with increases in peroxidase (POX) and polyphenol oxidase (PPO) activity but showed no correlation with concentrations of α‐pinene and β‐pinene or total phenolics. Furthermore, POX induction in stem tissue was cumulative and was greatest after three repeat treatments with UV‐C at 6, 3 and 1 week before inoculation. In contrast to UV‐C, MeJA induced a significant increase in β‐pinene concentration in stem tissue but did not affect PPO activity. POX activity was induced by MeJA in stems, although to a lesser extent than by UV‐C, but was not affected in needles. This appears to be the first report demonstrating the use of UV‐C radiation to induce resistance to fungal infection in a coniferous species. The implications of the underlying differences between UV‐C‐ and MeJA‐mediated resistance to D. pinea are discussed.     

Identification and expression pattern of a glutathione S‐transferase in Echinochloa crus‐galli

Plant glutathione S‐transferase (GST) forms a major part of the herbicide detoxification enzyme network in plants. A GST cDNA was isolated from Echinochloa crus‐galli and characterised. The gene, designated EcGST1 (E. crus‐galli GeneBank no: JX518596 ), has a 684 bp open reading frame predicted to encode a 25 kD protein. Sequence alignment showed that EcGST1 is a GST homologue. Its expression in response to quinclorac treatment was monitored in seedlings (leaves and roots) and adult plants (leaves, roots, stems and seeds) of quinclorac‐resistant (R) and susceptible (S) biotypes of E. crus‐galli. EcGST1 expression was 1.5–3 times greater in the R plants than in the S plants. However, after exposure to quinclorac, the difference in the expression levels of EcGST1 in R plants, compared with S plants, increased to a ratio of 6–10. Enhanced EcGST1 levels should enable greater quinclorac detoxification following quinclorac stimulation in R plants. GST‐based metabolism may be partially responsible for resistance to quinclorac in E. crus‐galli. The results suggest a new resistance mechanism for this R biotype in Chinese rice fields.     

Influence of variety on the within-plant distribution of cassava green spider mite (Acari: Tetranychidae), and leaf anatomical characteristics and chemical components in relation to varietal resistance

The within-plant distribution of the cassava green spider mite, Mononychellus tanajoa Bondar, and the anatomical characteristics and the chemical components relating to varietal resistance of cassava, were studied using 11 cassava genotypes with varying levels of resistance for two dry seasons and one wet season. The results show that M. tanajoa aggregates on the top leaves of cassava at low levels of resistance as compared with a more even within-plant distribution at higher levels of resistance. Thus, for accurate sampling of mite populations, it might be important to consider young and old leaves, not just the young leaves, in fields containing resistant and susceptible cassava genotypes. Correlations between the anatomical characteristics and mite population density and damage scores were not consistent across months, either within or over seasons. This suggests that leaf anatomical characteristics may not be important in the varietal resistance of cassava to M. tanajoa. During the dry season, mite population density was positively correlated with leaf nitrogen, potassium and phosphorus and negatively correlated with leaf calcium and fat. Only calcium was negatively associated with mite damage at the peak of the dry season (January 1993 and 1994). Breeding cassava genotypes with high levels of leaf calcium and fat, and low levels of leaf nitrogen, potassium and phosphorus, may improve the level of resistance to M. tanajoa.     

Conservation tillage systems for sorghum production under semi‐arid conditions in India

Abstract

Field research was conducted near Hyderabad, India, during 1981 and 1982 to investigate zero‐tillage and reduced‐tillage systems for production of sorghum (Sorghum bicolor (L.) Moench.) under semi‐arid tropical conditions. Part of the investigation compared post‐seeding hand weeding and herbicide treatments for weed control efficacy. The results showed that shallow pre‐seeding tillage was just as effective as deep cultivations in producing high sorghum fodder and grain yields provided weeds were controlled after crop emergence. Both tillage regimes were more effective than a no tillage regime which received only a mixture of glyphosate and 2,4‐D prior to seeding. Post‐seeding weed control practices were essential to maintain high fodder and grain yields of sorghum. Hand weeding and inter‐row blade harrowing were more effective than atrazine applied pre‐emergence or 2,4‐D applied post‐emergence.