THE EFFICACY OF WINDBREAKS IN REDUCING THE SPREAD OF CITRUS CANKER CAUSED BY XANTHOMONAS-CAMPESTRIS PV CITRI

The effects of windbreaks and copper (Cu) bactericide applications alo ne and in combination on the spread of Xanthomonas campestris pv. citr i (Xcc) and incidence of citrus canker were tested in Argentina during 1990 and 1991. The monomolecular temporal model was the most appropri ate for describing citrus canker disease progress. The monomolecular r ate of disease progress was significantly less for Cu bactericide and windbreaks compared to an untreated control; however, more significant reductions of disease progress occurred with the use of windbreaks al one or in combination with Cu bactericide. Disease gradients were sign ificantly less extensive when a Cu bactericide was used compared to un treated control plots, with significant additional reductions when win dbreaks were employed. Temporal and spatial analyses of citrus canker epidemics the indicated that the use of windbreaks was a moro effectiv e disease control use of a Cu bactericide and significantly reduced te mporal disease increase and spatial spread of citrus canker over time. As expected, Cu bactericide did reduce disease increase and spread bu t not as effectively as windbreaks. Temporal increase and spatial spre ad of disease associated with A-strain and B-strain of Xcc in lemon pl antings were not significantly different indicating that for a suscept ible host such as lemon, the two strains are equivalent in virulence a nd epidemiological potential.