VARIATION IN SUSCEPTIBILITY OF GRAPEVINE PRUNING WOUND TO INFECTION BY EUTYPA-LATA IN SOUTH-WESTERN FRANCE

Grapevine cultivars Cabernet Sauvignon (susceptible to Eutypa dieback) , and Merlot (tolerant), were pruned three times during the dormant se ason (mid-December, mid-January and mid-February) and wounds on the 1- year-old canes were inoculated weekly with ascospores of Eutypa lata a fter pruning. No differences in susceptibility to infection were obser ved between cultivars, although in the vineyard they differed in sympt om expression. Infection by E. lata varied with pruning date and the a ge of the pruning wound, and was higher and of longer duration with ea rly pruning (December). At low temperature, infection of the pruning w ounds by E. lata was increased, whereas the growth of other microorgan isms was reduced. Moderate temperatures encouraged the growth of other microorganisms, notably Rhodotorula sp. This natural colonizer of gra pevine 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 da ys after application of the wound colonizer, infection being reduced b y 95-100%.