By Jen Llewellyn,
OMAFRA Nursery Crops Specialist

What ever happened to “Spring” in Ontario?

When I was a kid, we had so much snow in the winter that we would build snow forts that were 10 feet high. When I was a kid, we always had a white Christmas. When I was a kid, April was a dreaded month for walking to school because of all the rain, mud and cool weather. Now we seem to go from winter to summer, with lots of drying winds. The warm spell that we experienced from mid-late April turned the landscape and nursery upside down. Container crops that are normally forced for sale in May were blooming by the third week of April. Field production nurseries were also thrown into a tizzy. The window for spring digging bare root material was wickedly short since some species had already broken bud by the fourth week of April, resulting in the failure to meet orders and a bottle-neck in the production cycle.  The weather generated early interest from the consumer and for landscape installations, but there were still too many days before the last frost-free date in May to plant actively growing ornamentals.
 

Pest watch for May

Hopefully the populations of adult Japanese beetles (Popillia japonica) will be significantly low in 2008. The hot, dry conditions we had during early grub development last summer should have reduced the successful development of a good percentage of the grubs in the soil. The last major population peak for this beetle was about 10 years ago, followed by a fantastic population crash after the wickedly dry summer of 1998. Viburnum leaf beetle has been a real challenge on several viburnum species, often causing significant dieback and mortality in just two to three years of defoliation. This spring I am conducting a small efficacy trial to test out some of the “softer” insecticidal products that may be exempt from pesticide regulations and ban. I’ll let you know how it turns out. Fletcher scale and euonymus scale continue to plague established conifers and broadleaf evergreens. Opportunities to apply insecticides at the crawler stage will be especially important this year.

Gymnosporangium is the genus of fungus that is responsible for pear trellis rust, hawthorn rust and cedar-apple rust. Where pear trellis rust was a problem last year, monitor juniper hosts for Gymnosporangium rust sporulation (bright orange gelatinous masses, bright orange powdery masses) in May and early June. Gymnosporangium tends to sporulate on juniper hosts when the weather is warm and rainy. These spores will land on the alternate hosts: pear, apple, crabapple, hawthorn etc. and cause unsightly orange lesions, followed by projectile fungal structures in late summer. Nova is registered to help manage foliar diseases like Gymnosporangium rusts.

Diseases and insect pests in May
a) In areas where the following indicator plants (100-150 GDD Base 10oC):
    Aesculus hippocastanum (horsechestnut) are in full bloom.
    Syringa vulgaris (common lilac) are in full bloom.
    Spiraea x vanhouttei (bridalwreath spirea) are in full bloom.
    b) In areas where the following phenology plants 150-250 GDD Base 10oC):
   Aesculus hippocastanum (horse chestnut) are in full to late bloom
   Spiraea x vanhouttei (bridalwreath spirea) are in late to finished bloom
   Syringa vulgaris (common lilac) are in late to finished bloom
   Robinia pseudoacacia (black locust) are blooming
    Check out OMAFRA Publication 383, Nursery & Landscape Plant Production and IPM for more detailed monitoring tables (Chapter #3). To order, call 1-800-668-9938.

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Jen Llewellyn can be reached at (519) 824-4120, ext. 52671 or by e-mail at jennifer.llewellyn@ontario.ca