RESULTS OBTAINED IN 1980 FROM AVOCADO ROOT ROT FIELD TRIALS

SUMMARY The effects of certain orchard practices and anti-fungal compounds on Phytophthora cinnamomi-induced root rot in avocados were tested in five field trials. In the case of badly diseased, mature trees, severe pruning temporarily improved tree condition. This effect was enhanced by applications during summer of either fosetyl-AI sprays at 4 to 6week intervals or metalaxyl granules or soil drench, applied 2 or 3 times. At one site, the beneficial effect of fosetyl-AI was evident for 18 months after the last application to stag horned trees and for 30 months in the case of un-pruned trees. In two trials where metalaxyl and fosetyl-AI were compared on mature trees, metalaxyl gave better results in one case, while fosetyl-AI was more effective in the other. A combination of these two products gave excellent results. Ethazol was tried in one experiment, but its performance was disappointing.