Aetiology, Epidemiology and Control of Measles
Nine vineyards in California, including four table and five wine grape, were surveyed for measles throughout the 1997 growing season. Ratings of fruit and foliar symptoms were recorded for an acre of grapevines at each site in order to make a correlation between incidence and severity of measles and environmental conditions (data pending). Two healthy and two infected grapevines from each vineyard were selected in order to compare weights and soluble solids of the fruit. At all the sites the healthy fruit weighed more than infected fruit. Brix readings taken of healthy grapes were also higher at most sites except Kern and Tulare-1 where infected grapes were 0.7 and 1.0 brix reading higher than healthy grapes respectively. Entire grapevines were excavated and isolated from in order to determine the exact locations on the vine where Phaeoacremonium spp. reside. P. chlamydosporum was isolated from cordons, trunks and roots and P. inflatipes was isolated from cordons and trunks. Pathogenicity test using P. inflatipes and P. chlamydosporum resulted in 70.8%and 66.7%mortality of grape seedlings respectively. Inoculations of grape wood cuttings with P. inflatipes resulted in over 60%recovery of the fungus from necrotic tissue. Fugicides commonly used in vineyards were tested for growth inhibition of Phaeoacremonium spp. with Benlate and Procure limiting fungal growth most effectively after 7 days. Bayleton, Rally, Rubigan and sodium arsenite had little effect on the growth of P. inflatipes but growth inhibition was more significant against P. chlamydosporum.