Project Code: BPR13-080
Project Lead
Nancy Cain Cain Vegetation Incorporated
Objective
To develop efficacy and crop tolerance data in support of a regulatory submission for Grandevo (MBI-203 DF) for the management of Fletcher scale (Parthenolecanium fletcheri) in yew (Taxus species)
Summary of Results
Background
Fletcher scale is a relatively common pest in ornamental nurseries in Southern Ontario and Quebec. Scale insects cause direct feeding damage, which manifests as chlorotic tissue, by sucking plant fluids from yew plants. Secondary damage from sooty molds results from fungi growing on sugary honeydew secreted by scale crawlers. During the 2012 Biopesticide Priority Setting workshop in Canada, Grandevo™ (MBI-203 DF) was selected by Canadian growers for the management of Fletcher scale in the outdoor ornamental yew.
Grandevo™, containing fermentation solids of Chromobacterium subtsugae strain PRAA4-1, is a biological insecticide/miticide developed by Marrone Bio Innovations, Incorporated. The product is registered in the United States for use against various pests of ornamental plants and edible crops. This project involved a trial conducted in Ontario from June 2013 to June 2014, to determine the efficacy of Grandevo™against Fletcher scale in yew and to test tolerance of the crop to the product.
Approaches
Yew plants grown in large containers were used in the trial, which consisted of four replicates of four plants per plot. Treatments included two rates of Grandevo™ (2 kilograms per hectare (kg/ha) and 3 kg/ha), with 3 applications per season starting at emergence of scale crawlers. Malathion 500 EC was used as the commercial standard treatment. Parameters of efficacy evaluation included scale crawler number, severity of sooty mold contamination (scale 0 to 1, where 0 equals no contamination and 1 equals 100 percent (%) of plant shoots contaminated), and foliar feeding damage (scale 0 to 10, where 10 equals all leaves on sampled shoots are symptomized with chlorosis).
Results
The trial naturally developed the sufficient scale crawler pressure for evaluating the product efficacy when the product was applied in July, 2013.
Trial results showed that the low rate of Grandevo™ (2 kg/ha) did not provide effective crawler control at any of the sampling times, while the high rate (3 kg/ha) reduced scale crawler number by approximately 50% compared with the untreated plots at most sampling times. This reduction in scale crawler numbers remained in evidence three months after applications, and was also observed in June, 2014, eleven months after the first application, with adult scale numbers reduced as compared with untreated control by approximately 45%. The efficacy provided by the high rate Grandevo™ (3 kg/ha) was comparable to that provided by the commercial standard treatment.
The higher rate treatment of the product also reduced black sooty mold leaf contamination and foliar chlorosis from feeding. The sooty mold contamination rating indicated that sooty mold in the higher rate treatment (3 kg/ha) was approximately 70% lower at harvest when compared to untreated leaves. Feeding damage (chlorosis) on leaves was significantly reduced in treated plants within the first two months after treatments.
The product applications did not result in any phytotoxicity in yew plants in the trial.
Conclusions
A rate of 3 kg/ha of Grandevo™ provided effective control of scale insects present as a heavy infestation. It is probable that this rate treatment would provide an even more complete control in the case of lighter infestations of scales.
The data generated in the trial is included in a regulatory data package to support the registration of Grandevo™ in Canada.