Grapevine cultivars Cabernet Sauvignon (susceptible to Eutypa dieback), and Merlot (tolerant), were pruned three times during the dormant season (mid-December, mid-January and mid-February) and wounds on the 1-year-old canes were inoculated weekly with ascospores of Eutypa lata after pruning. No differences in susceptibility to infection were observed between cultivars, although in the vineyard they differed in symptom expression. Infection by E. lata varied with pruning date and the age of the pruning wound, and was higher and of longer duration with early pruning (December). At low temperature, infection of the pruning wounds by E. lata was increased, whereas the growth of other microorganisms was reduced. Moderate temperatures encouraged the growth of other microorganisms, notably Rhodotorula sp. This natural colonizer of grapevine pruning wounds was able to reduce the infection capacity of E. lata. It was more effective when inoculation with E. lata was carried out with low numbers of ascospores and when it was delayed until 14 days after application of the wound colonizer, infection being reduced by 95-100%.
During a 5-year period (1993-1997), the release of Uncinula necator (Schweiniz) Burrill ascospores was monitored under natural conditions in the Bordeaux region. Ascospore release always began after bud burst and generally ended before blossoming. The release periods of ascospores were always associated with a rainfall higher than 2 mm, a wetting duration greater than 2.5 h, an average temperature generally above 11°C and a daily mean temperature sum from November 1 to the first ascospore release above 1100°C. There was no relation between earliness, number of ascospores released, and disease severity on grapes (Vitis vinifera L. cv. Merlot). The primary infection did not appear to be important for the increase of the powdery mildew population; on the other hand, the weather conditions of April (rainfall and temperature) seemed to strongly influence disease severity on berries by enabling good growth of the pathogen on leaves. These findings could be used to determine the optimal dates of the first fungicide treatments for powdery mildew according to the weather conditions.Key words: cleistothecia, ascospores, release, weather conditions, powdery mildew, Uncinula necator, grapevine.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.