Margaret Lauterbach

Keeping our roses sweet requires a vigilant fight against bacterial cane blight

The Julia Davis Park Rose Garden is a Boise treasure, and its caretakers are trying to make sure that a bacterial disease that was vicious in 2010 doesn’t take such a toll ever again.
The Julia Davis Park Rose Garden is a Boise treasure, and its caretakers are trying to make sure that a bacterial disease that was vicious in 2010 doesn’t take such a toll ever again. kjones@idahostatesman.com

A few years ago, rose growers and vendors found a “new” disease killing rose shrubs in our area. Krishna Mohan, plant pathologist for the University of Idaho lab in Parma at that time, identified the disease as an unknown pathovar of a bacterial disease that afflicts lilacs, Pseudomonas syringae. Apparently it’s occurring not just here, but in other locations where growers perhaps have paid little attention, just chalking up the losses to winter kill.

Winter-killed canes are black and dry beneath the bark. Those afflicted by this disease may appear very dark, but if one scrapes the disease-affected bark with a thumbnail and finds that it’s oozing liquid and that the color of the cane beneath the bark is dark brown to red in color, then it’s this disease we now call bacterial cane blight.

Andrea Wurtz is in charge of the Julia Davis Rose Garden for Boise Parks and Recreation, and she said they had only a small loss of rose shrubs in that extensive garden this year.

They have changed their treatment of the rose shrubs over the past few years. They had huge losses in 2010, but since the disease was identified, they began treating infected shrubs, and lately changed the treatment’s timing, so now there is just a fraction of the losses. They used to use a drench of a copper-based chemical in autumn and early spring, but since Wurtz began noticing symptoms of the disease in August, they now are using that copper sulfate-based bactericide (Phyton) during an August cooling period.

Warning signs of the disease are reddish-brown areas on the bark, mainly at wounds or leaf scars. In the spring of 2011, they found one-quarter of the rose garden’s 2,000 shrubs had been killed. This is a huge rose garden. Do they deadhead? The amazing response was yes, they do prune off spent blossoms, with the aid of volunteers from the Idaho Rose Society. This huge rose garden is one of the special amenities of this city, one treasured by long-time residents.

If you grow or even love roses, join the Idaho Rose Society. Dues are only $10 per year per person, or $15 for a family membership. The group meets the first Monday evening of the month from March to October at 6:30 p.m. (unless the Monday falls on a holiday, and then the meeting is delayed for one week). Check Facebook for the Idaho Rose Society’s information and location of their next meeting. Anita Gonzalez is the president.

Critter alert

This valley is full of raccoons and skunks, both loving pet food. Please don’t feed your dog or cat outdoors where these destructive critters can get to the food. They also will steal sweet corn unless you use shipping tape to tape the ear firmly to the stalk. A wrap around the ear, then extend the tape to a wrap around the stalk. Squirrels might get into it anyway. During their rampage, raccoons or squirrels will damage your garden.

Skunks may dig up your lawn and garden in their quest for luscious grubs or your prized earthworms. Unfortunately, they probably won’t get all of your grubs or other lawn pests, and they’re not concerned with the appearance of your lawn or the fragrance of your dog.

It’s just best not to attract either one to your garden area. We’ve maintained a birdbath in the front yard and the garden in the backyard, where we do not supply water. Raccoons lack salivary glands, so dip or “wash” their food in water when they eat. Not having water close by might discourage their thievery. So far we’ve been lucky that squirrels haven’t bitten into ripening tomatoes in search of water, but I do harvest tomatoes when they begin to color to prevent that. If I don’t see tomatoes turning color, squirrels apparently don’t either, for I have found tomatoes in dense foliage that are quite ripe. That’s another indicator that tomatoes do not need direct sun exposure for ripening.

Send garden questions to melauter@earthlink.net or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.

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