grafted on resistant sour orange stocks, show high incidence of infection in the Resistance of 70 citrus genera, species, and cultivars to Phytophthora citrophthora was eastern Mediterranean area. This paper investigated during winter dormancy.

According to the results of bioassay studies, 50 p.p.m. and higher dosages of fentin acetate inhibited the growth of Phytophthora citrophthora in situ. Zoospore movement of P. citrophthora varied between 3 and 15 min at 0.5, 1, 10, 100 and 500 p.p.m. fentin acetate. The fungicide also inhibited fruit infections caused by P. citrophthora zoospores at 5 p.p.m. concentration, and protected citrus seedling roots against infection by the fungus at 20–50 p.p.m. concentrations in water culture. Fruit infection was significantly lower in fentin acetate plots than in those without fungicide applications. Stem infection was 15.5 and 8.3% when fentin acetate was applied one or three times respectively as a soil drench in a lemon orchard, but reached 74.9%) in control plots. Fentin acetate treatment decreased inoculum potential to 1/2 and 1/128 in the root zone from the first to the third application.