Trials Using Containerized Trees
In this field trial, the efficacy of polymer and menthene products as plant-protectants are being assessed experimentally on containerized olive plants exposed to natural inoculum.
Containerized plants will be arranged in a randomized complete block design, with 8 treatments: 2 Cu treatments (+/- Kocide), and 4 plant protectant treatments (Nu-Film P, Vapor Guard, Anti-Stress 550, and untreated). Season 1 of this trial was established in December 2010, and treatments were applied to 1 year old Manzanillo, 1 year old Arbequina, and 2 year old Arbequina. The study was established across varieties and ages because olive susceptibility to P. savastanoi has been shown to vary by plant age and cultivar (12).
In addition to application of treatments, twenty labeled leaf scars (Fig. 1) were manually exposed on the 2 year old plants in order to directly assess protection of leaf scars from infection. Within 4 days of treatment, plants were moved to a heavily infested orchard on the UC Davis campus. This particular site is ideal for olive knot management research because the lack of disease management practices over decades has fostered a large pathogen population in the absence of a selection pressure (ie. copper). Because recent infection of oil olive plantings is evidence of natural inoculum potential, blocks of treated, containerized plants were established in the orchard (Fig. 2).
Data on plant disease development is being collected in Summer 2011 and the experiment will be repeated with addition or deletion of treatments during the 2011/2012 and 2012/2013 winter rainy seasons.
- Disease incidence is recorded (frequency of plants infected).
- Disease severity is recorded; severity is determined by both excising galls and measuring dry weights of gall tissues, and counting number of galls developing on labeled, exposed leaf scars.
- Residual Cu is determined by comparison of plant tissue analysis between treatments, with untreated control leaves serving as a baseline(Fig. 3).
- Environmental conditions are monitored throughout the experiment to assess potential influence of temperature, precipitation, and solar radiation on Cu persistence on the leaf surface. (Fig. 4)
Photos by Elizabeth Fichtner, UCCE Farm Advisor, Tulare Co., CA
Fig. 4 (below). Environmental conditions including precipitation, temperature, and solar radiation, were monitored throughout experiment.