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Effect of Nemarioc-AL, Nemafric-BL and Penicillium simplicissimum on avocado root rot and mineral nutrient concentrations

Ndivhuwo David Mamphiswana: University of Limpopo

<div>Worldwide, <em>Phytophthora cinnamomi</em>-induced avocado root rot is a major disease, which causes rotting of feeder roots and general tree decline, with poor nutrient and water uptake, which result in plant death. Following in vitro efficacy trials, the fermented plant extracts [Nemarioc-AL (AL), Nemafric-BL (BL)] and biological agent [<em>Penicillium simplicissimum (</em>PS)] were investigated on avocado root rot suppression in a 2 × 2 × 2 factorial experiment under greenhouse conditions. Treatments were arranged in a randomized complete block design, with nine replicates. At 24 weeks after inoculations, the second order interaction had no significant effects on plant growth variables; whereas the first order interactions had some significant effects. The AL × BL and BL × PS interactions were each not sufficiently effective in reducing root rot and foliar symptoms in comparison to individual factors. For instance, AL reduced root rot by 30%, whereas AL × PS interaction reduced the variable by 4%. Second order interaction for nutrient elements was, except for nitrogen in root tissues, not significant. Relative to the control, AL × BL × PS interaction increased nitrogen in root tissues by 89%, which was lower than those of individual factors. First order interactions such as AL × BL, BL × PS, AL × PS were significant for number of nutrient elements in root and/or leaf tissues. However, the combined effect of the products was lower than when applied individually. Results suggested that the three products should be applied separately in the management of avocado root rot.</div>