Concepció Moragrega

Evaluation of a Reduced Copper Spraying Program to Control Bacterial Blight of Walnut

Walnut blight, caused by Xanthomonas arboricola pv. juglandis, is currently controlled in western Europe through a standard schedule of seven applications of sprayed copper from bud break until harvest. A reduced spray schedule, with the last four applications omitted, was compared to the standard program in experimental plots for 3 years. Bacterial population levels in the spring were not significantly different between trees subjected to reduced sprays and those subjected to the standard schedule, but in summer they were higher in the trees that received fewer sprays compared with the standard program. However, disease control on nuts was similar or even better with the reduced spraying program than with the standard program, with the additional economic benefit of four fewer copper applications. After 3 years of using the reduced spray program, the amount of copper accumulated in the soil was significantly lower (about half) than that found in the soil where the standard spray program was implemented.

Susceptibility of selected European pear cultivars to infection by Stemphylium vesicarium and influence of leaf and fruit age.

Nonwounded fruit of 16 European pear cultivars (Pyrus communis) and potted Conference pear plant were inoculated with conidia of Stemphylium vesicarium. Cultivars Passe Crassane, Alexandrine, Conference, Doyenne du Comice, Duc de Bordeaux, Abate Fetel, and General Leclerc were highly susceptible. Cultivars Williams, Blanquilla, Beurre Hardy, Louis Bonne, Grand Champion, and Highland were slightly or not susceptible. The susceptibility of fruit decreased logarithmically from fruit set to harvest in very susceptible cultivars. Younger leaves developed 1.8-3 times more disease than older leave

Apical Necrosis and Premature Drop of Persian (English) Walnut Fruit Caused by Xanthomonas arboricola pv. juglandis

Etiological and epidemiological aspects of apical necrosis of walnut fruit were studied on cultivars Chandler, Franquette, and Hartley in a Spanish walnut orchard during 2007 and 2008. Affected fruit showed brown necrosis beginning at the blossom end of nuts; these symptoms differed from lesions of common blight of walnut (Xanthomonas arboricola pv. juglandis). X. arboricola pv. juglandis was consistently isolated from apical lesions throughout the growing season. Field isolates reproduced symptoms observed in the orchard when inoculated on immature detached walnut fruit in the laboratory. Sporadic occurrence of Fusarium spp. and Alternaria spp., mainly in dropped fruit, was attributed to secondary colonization of apical lesions that were originally caused by X. arboricola pv. juglandis. Apical necrosis and common blight were similar in disease epidemiology and cultivar susceptibility; a major increase in epidemics occurred at initial fruit development, and cvs. Chandler and Hartley were more affected than cv. Franquette. Our results suggest that apical necrosis is a new manifestation of walnut blight characterized by distinct symptoms and severe premature fruit drop.

An update on control of brown spot of pear

Brown spot of pear is a fungal disease producing high economical losses in several pear-growing areas in Europe. Fungicide applications during the growing period either at fixed schedule or delivered according to the BSPcast forecasting system are not enough to control the disease under favorable conditions. New strategies have been introduced to control the inoculum production using sanitation methods. These methods are based on combinations of leaf litter removal during winter and biological control agent applications during late winter, spring and summer. These practices reduce both the inoculum pressure and disease levels. Therefore, the resulting optimized disease management consists of a combination of sanitation methods applied during the whole year with chemical fungicides scheduled according to the BSPcast forecasting model during the vegetative period. It is expected that the control of brown spot could be further refined upon availability of rapid methods for inoculum potential analysis. However, this analysis is difficult due to the variability in pathogenicity within the pathogen population.

Evaluation of drench treatments with phosphonate derivatives against Pseudomonas syringae pv. syringae on pear under controlled environment conditions

AbstractSeveral phosphonate derivatives including theoomycetic antifungal agents phosphonate andtris-o-ethylphosphonate (fosetyl), theethylene-releasing compound 2-chloroethylphosphonate(ethephon), and the antibiotic2-epoxypropylphosphonate (phosphomycin) were evaluatedfor in vitro and in planta activityagainst Pseudomonas syringae pv. syringae.Inhibition of colony growth in CYE agar byphosphonate, fosetyl and etephon was very slight(minimal inhibitory concentrations MIC= 0.31–;0.62 gHP

Interaction of antifungal peptide BP15 with Stemphylium vesicarium, the causal agent of brown spot of pear.

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Combined morphological and molecular approach for identification of Stemphylium vesicarium inoculum in pear orchards.

/l). Also, survival of P. syringae pv. syringae in aqueous solutions ofphosphonate or fosetyl was high. Only phosphomycinshowed significant antibacterial activity invitro (MIC=10-20 µg HP