Aetiology, Epidemiology and Control of Measles

Eight vineyards, including four Thompson Seedless and four Cabernet Sauvignon were surveyed during the 1997-98 growing season for foliar and fruit symptoms of measles. Each vine was evaluated for disease incidence and severity with severity scored on a scale of 0 (= no symptoms) to 5 (= complete foliar and fruit symptoms). Disease incidence increased for each vineyard over time but average severity for each plot did not follow a similar trend, decreasing at different times of the growing season for different vineyards. In 1997-98, SLO-2 had the lowest foliar and fruit incidence and severity. Tulare-1 had the highest foliar incidence and severity in 1997-98 but only had the highest fruit incidence in 1997 while SB had the highest incidence in 1998. Tulare-1 had the second highest fruit severity in 1997 and the highest severity in 1998. It also had the greatest yield loss for both years with 4,115.5 and l,164lbs in 1997-998 respectively. SLO-2 had the least amount of yield loss in 1997 with 163.91bs and 131. libs in 1998. Several systemic fungicides, such as propiconizol, myclobutanil, and Foscheck, are being screened for growth inhibition oi Phaeoacremonium inflatipes and P. chlamydosporum. Fungicide trials were set up using three different methods:

  1. Three 60cc syringes with 50ml of fungicide solution were inserted into predrilled holes around the base of the vines.
  2. An injection gun, which forced the fungicide solution into the xylem vessels of measles infected vines.
  3. Fungicide applications were placed in fresh girdling wounds of infected Thompson Seedless vines.

A field trial has been setup at the U. C. Davis, Department of Plant Pathology Field Station, which includes 150 Thompson Seedless and 150 Red Globe, in order to test different applications of fungicides, which will protect the young plants from infection.