May 15, 2010
By Jen Llewellyn
OMAFRA nursery crops specialist

Every March, Peter Isaacson, CNLA’s Minor Use Coordinator, and I attend the workshops in Ottawa on the Minor Use program. It helps to improve growers’ access to newer, safer pesticides in Canada. Established in 2003 by Agriculture and Agri-Food Canada (AAFC), the program is administered by the Pest Management Centre in Ottawa.

The annual workshops are where industry, registrants and government come together to decide what pest management issues should be addressed through government-funded research (e.g. efficacy and crop tolerance trials). Each day of the three-day meeting has its own theme: entomology, pathology and weed management.  Registrants are invited to give a brief presentation on up-and-coming pest management products, many of which are reduced risk and biological pesticides. One participant dubbed it, “speed dating in pest management.” As you can imagine, it’s a great networking event for IPM.

For all the commodities represented, we must decide on only 10 ‘A’ priorities that will be addressed through research from any of the given themes. That is not a lot. But each year, Peter and I work closely with the nursery, landscape and conifer industry representatives across Canada. We have managed to secure quite a few projects for outdoor ornamentals (nursery and landscape). This year outdoor ornamentals secured an ‘A’ priority for a new pre-emergent herbicide (dimethenamid-p, Frontier Max) for container and field production. Outdoor ornamentals also received an ‘A’ priority for the biopesticide, Bacillus subtilis, against root rots. The ‘A’ priorities that were decided upon at this meeting will become efficacy and crop tolerance trials in the 2011 growing season. The data from these trials will be used to support a label expansion for those pesticides.  

Minor use in the U.S. is administered by a program entitled the IR-4 Project. In recent years, our Pest Management Centre and IR-4 have worked together to conduct joint research trials for new, reduced risk pesticides. At this meeting, we met with IR-4’s ornamental horticulture program manager, and we will be working together with Ottawa’s Pest Management Centre to plan and execute some joint trials for greenhouse and outdoor ornamentals. Some examples include herbicide screening trials for liverworts and insecticide screening trials for scale insects (Euonymus, Taxus).   

In the meantime, we have several minor use projects and submissions in the system. The year 2009 marked the completion of two, two-year fungicide screening trials for conifer needlecast diseases. The Pest Management Centre is currently reviewing the report and has pledged that they will submit the data and a request to expand the labels of the resulting top three fungicides from these trials. Last year, trials were carried out at commercial nursery sites for insecticides against aphids and leafhoppers. This year, researchers will conduct trials for the management of downy mildew and also borers (e.g. bronze birch borer) for nursery crops and landscape ornamentals in Canada.       

Boxwood blight research at the University of Guelph

Nurseries in several locations across Ontario have experienced outbreaks of disease on their boxwood crops for the last several years. The cultivars Green Gem, Green Mound, Green Velvet, and Green Mountain have been found to be most commonly affected.  Although this disease is not of major concern in outdoor production (where some branch dieback may result), or in the landscape, infection during the propagation phase of cuttings can lead to severe crop losses. Unfortunately, there is very little information on this disease in the scientific literature. Communication among OMAFRA, the nursery industry and the University of Guelph led to this research project where Dr. Tom Hsiang and Amy Fang Shi could help determine 1) the causal organism(s), 2) the spore production cycle of this pathogen(s), 3) how this disease can be managed more effectively.

Young boxwood plants were obtained from nurseries in Sept. 2008, Feb. 2009, May 2009, and Nov. 2009. The fungus Volutella buxi was isolated from these plant samples. The optimal growth temperature of V. buxi on artificial media was found to be between 20 to 25 C. Approximately 40 to 50 per cent of the spores of V. buxi start to germinate within 12 hours under moist conditions. By 48 hours, 80 per cent of the spores have germinated and some germ tubes begin to branch. Among 32 V. buxi isolates from boxwood plants, there are significant differences in the rates of growth and germination.

To assess the susceptibility between boxwood cultivars, Green Gem, Green Mountain and Green Velvet were inoculated with a 140L of a 106 spores/ml suspension of V. buxi. In this test, Green Gem was the most susceptible cultivar. Only the undersides of leaves showed symptoms after inoculation, while none of the inoculated upper leaf surfaces showed symptoms.

A fungicide test, using leaves in Petri plates, was conducted to investigate curative and residual activity of fungicides and the duration of time (pre- and post-inoculation applications) where fungicides are efficacious against boxwood blight on inoculated detached leaves. Results showed that pre-inoculation fungicidal treatments were much more effective in preventing or decreasing symptoms. More fungicide tests in controlled environments are planned for 2010. The researchers are also conducting a survey to help determine the sporulation period for Volutella buxi in outdoor nursery production. 
Jennifer Llewellyn may be reached at 519-824-4120, ext. 52671, or by email Read her Nursery-Landscape Report: