Effectiveness of Metalaxyl and Fosetyl Al AgainstPhytophthora parasiticaon Sweet Orange

Abstract

In a 3-yr study, metalaxyl and fosetyl A1 were evaluated as soil drenches, trunk paints, and foliar sprays for control of Phytophthora parasitica in newly planted sweet orange trees [Citrus sinensis] on sweet orange rootstock. After application of metalaxyl as a soil drench or trunk paint, fungitoxic activity, as determined by bioassay, persisted for 3-4 mo in twigs and roots during the first 2 yr. In the third year, activity was less, probably because of dilution of the fungicide in the larger trees. Fungitoxic activity was less when metalaxyl was applied as a foliar spray. Application of fosetyl Al by all methods only occasionally produced fungitoxic activity detectable by bioassay. Both fungicides reduced foot rot incidence, but none of the treatments increased growth of the trees compared with untreated controls, indicating that root rot may have been of minor importance.