Control of Eutypa Dieback of Grapes

Several objectives were investigated in 1996-97, the primary short term objective of this research is to find an effective control of Eutypa dieback, caused by the fungus Eutypa lata. In the field, fungicides (Benomyl, Cinnamyl Aldehyde, Boric acid, Soap, Lime Sulfur, Nectec Paste, HCA CARN, HCA EEE, Proguard A,B,C and Gel, Fusarium lateritium, Cladosporium herbarum and Agriquest microbe) were applied in 4 locations (Davis, Lodi, Sonoma Co. and Yolo Co.) on different grape cvs. (Cabernet Sauvignon, Grenache, Petite Sirah, Semillon). The percent of infected spurs will be correlated to the fungicide and the control. Susceptibility of grapevine cvs. will also be compared by measuring lesion expansion after inoculation of the spur or the cordon of different grapes cvs. (Cabernet Sauvignon, Merlot, Malbec, Viognier, Sirah). Phenotypic differences will be noted and associated to time of budbreak and shoot lignification in each cvs. In vitro experiments showed that the fungicides (Benomyl, Soap, Break…) and biocontrols {Fusarium lateritium) have an effect on the mycelial growth of the fungus. Combination of biocontrol fungi and fungicides have been tested in the lab in order to obtain better protectant activity. A new in vitro technique has been developed and is being used to compare the efficacy of fungicides in preventing colonization of the wood by Eutypa lata mycelium. Moreover, a lab and a greenhouse model is being established in order to test fungicide trials on living plants as a pre vineyard screen and to determine cultivar differences. A new part of this research concerns the physiological and biochemical aspect of the host-pathogen interaction. We have shown that some phenolic compounds have an effect on the mycelial growth of the fungus (on PDA), this effect being associated with the pH of the media. Finally a technique of DNA extraction on Eutypa lata has been established, and the determination of a wide range of the Eutypa population will be done by PCR to evaluate the heterogeneity of the California Eutypa population in order to try to pinpoint sources of inoculum.