Adaptation of reduced risk pest management strategies for the ornamental nursery industry in Canada

Project Code: PRR06-430

Project Lead

Peter Isaacson - Canadian Nursery Landscape Association

Objective

To evaluate the efficacy of three biofungicides (Gliocladium catenulatum, Trichoderma harzianum, Bacillus subtilis) and one microbial insecticide (Metarhizium anisopliae) on ornamental nursery stock and greenhouse plants; to incorporate these products into nursery production practices; and to effectively deliver the technologies to growers

Summary of Results

Background

Prior to the initiation of this project, nursery growers had identified the need for biological control products and information on their use to facilitate the adoption of sustainable pest management approaches. The few microbial products available at the time in the Canadian marketplace, including Bacillus thuringiensis var. kurstaki, B. thuringiensis var. israelensis and Agrobacterium radiobacter, accounted for less than 5% of the total active ingredients used by the industry. Pest management was still predominantly dealt with culturally and chemically.

Diseases such as botrytis, rhizoctonia and powdery mildew are problems in outdoor grown nursery stock and greenhouse plants. Among insect pests, weevils are one of the most damaging and difficult to control in container production affecting over 140 species of ornamentals. These key pest problems consistently rank as top pest priorities for the nursery industry.

This project was initiated to increase the availability of microbial bio-control agents through the development of data to facilitate registrations or label expansions, develop approaches to incorporate these products into nursery Integrated Pest Management (IPM) and to effectively deliver the new technologies to growers.

Approach

The biological fungicides Trichoderma harzianum (Rootshield®, Plantshield®), Bacillus subtilis QST 713 (Rhapsody® ASOTM, Serenade® MAXTM) and Gliocladium catenulatum (Prestop®) were evaluated for efficacy and crop tolerance for powdery mildew on outdoor grown hybrid roses, botrytis on geraniums and rhizoctonia aerial blight of maidenhair fern, in comparison with standard fungicides.

The geranium and fern trials were conducted in commercial greenhouses and the rose trials were conducted outdoors. All trials were set up as a randomized complete block (RCB) design and were maintained under conditions that favoured disease development. Where necessary, host plants were inoculated to enhance disease development. Treatments were applied as foliar sprays at 14 day intervals. Disease incidence and severity was rated and the ratings subjected to statistical analysis.

To identify weevil species infesting containerized nursery stock, woody plants suspected of being infested were collected from nurseries in the Lower Mainland and Fraser Valley of British Columbia (BC) (102 plants in total). After two months, the weevils in each pot were identified and counted.

Trials were conducted on various plants artificially infested with weevils, to determine the efficacy of the microbial insecticide Metarhizium anisopliae in comparison to the nematode biological control (Steinernema kraussi) used by industry. The Metarhizium was incorporated into the soil at different rates utilizing a system for pre-germination. Treatments were assessed through the rating of root vigour and a count of weevil larvae recovered from the entire contents of each pot.

To assess the long term efficacy of M. anisopliae, pots of periwinkle that had been treated with M. anisopliae the preceding growing season, were inoculated with weevil larvae and the survival of larvae was evaluated one month later.

Growers were informed about the use of biological controls through presentations at grower meetings and written publications.

Results

On roses, preventative sprays every 7-14 days with any of the three biological fungicides, reduced powdery mildew symptoms when compared to the untreated checks, under conditions of moderate disease pressure. Disease control with Serenade® MAXTM and Prestop® was comparable to that obtained with NOVA 40W (myclobutanil).

Suppression of botrytis on geranium by Prestop® was most successful when treatments were applied preventatively and every 14 days. Prestop® reduced the number of botrytis lesions and the number of diseased leaves and provided a level of disease control comparable to Captan. Plantshield® was the only biopesticide in the study that significantly reduced rhizoctonia aerial blight on western maidenhair fern and control was equivalent to Senator 70WP. None of the products caused phytotoxicity symptoms on the test plants.

The predominant weevil species collected in this study of infested nursery stock was black vine weevil, (Otiorhyncus sulcatus). In trials involving impatiens plants, significantly fewer weevil larvae were recovered from M. anisopliae and nematode-treated pots than the controls. Levels of control were comparable in the Metarhizium and nematode treatments. In another study, healthy weevils were recovered in greater numbers from untreated pots than pots treated with Metarhizium the previous season.

Presentations (10) through the course of this project to the nursery and related industries in the key nursery growing areas of Canada, including a one day workshop in Kelowna, BC, helped to inform growers about the use of biopesticides. Two research updates were published in trades magazines and trial results for rhizoctonia aerial blight on fern were published in the 2008 Pest Management Research Reports (PDF) (Reports number 60 and 61). Data generated in these trials were used to support a regulatory submission for Metarhizium anisopliae for black vine weevil in nursery stock, and the use was registered by the Pest Management Regulatory Agency in February 2009.

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