Control of Eutypa Dieback of Grape
In 1997, an in vitro assay was set up to screen and quickly evaluate a fungicide potential prior to field trials. This method allows the testing of fungicide efficacy to Eutypa lata infection by looking at the colonization of grape wood blocks treated with specific fungicides. This test does not require the use of ascospores, no differences were observed in controlling the disease when the inoculation was done with E. lata mycelium or an ascospore suspension. A good correlation was generally observed between in vitro and in vivo trials for fungicide testing. Nectec paste and 1%Benlate in vitro prevented Eutypa colonization of grape wood blocks and also resulted in a high rate of protection of pruning wounds in field trials. However, Nectec paste formulation has changed in 1999 because propiconazole became unavailable for Janssen. Techniques have been set up to extract lignin, cellulose and hemicellulose from wood to measure their composition in different grapevine cultivars before and during infection and subsequent deterioration by E.lata and secondary fungi. Thus, the understanding of Eutypa pathogenicity is starting to be better understood. The fungus was shown to use glucose to grow in woody tissue. The epidemiology of E. lata in California is better known. Optimum temperature of ascospore germination and mycelial growth were established to be 20°C. Ascospore release was recorded at 4 different locations after rainfall. Fungi presenting characteristic ascospore morphology and mycelial growth of E. lata were found in these sites. The molecular probe that has been developed to identify E. lata from other grape pathogens, also identified these fungi to be different from E. lata. Work is underway to screen these fungi to see if they are pathogenic or are saprobes because their presence confounds the picture in terms of number of spores produced and conditions of their release.