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UMass Extension Landscape Message May 17, 2013

Posted by claire z6b Coastal MA (My Page) on
Fri, May 17, 13 at 16:05

UMass Extension Landscape Message May 17, 2013

From the Southeast Region (Hanson) report:
"...squirrels were observed biting off the buds on rhododendrons and clipping small branches on Corylopsis spicata to eat the developing seedpods."

"Impatiens downy mildew (IDM) was diagnosed on Impatiens (walleriana) in landscapes in Massachusetts for the first time in 2011 and devastated plantings in 2012. Over the past several weeks, IDM was confirmed in greenhouses in four counties in Michigan and in surrounding states. In each case, the disease was widespread within the greenhouse and losses were nearly 100 percent. Don’t get caught and have to replace plants this season. All Impatiens walleriana including double, mini and ‘Fusion’ are susceptible. New Guinea impatiens (I. hawkeri) and SunPatiens® and all other garden plants are not affected. Plant alternative shade plants this spring such as New Guinea impatiens, SunPatiens®, coleus, begonias (lots of types), torenia, lobelia, hypoestes and iresine.

The first signs of IDM are leaves that are slightly yellow or off color (not to be confused with lack of fertilizer). As the disease progresses, the undersides of the leaves will have white-colored, powdery-like spores. Sometimes it is difficult to see the spores without a magnifying glass. Eventually the leaves and flowers will drop off of the plant, and leave bare stems with only a few tiny, yellow leaves remaining. Downy mildew can be spread long distances by wind currents, water splash (overhead irrigation included) or by the movement of infected plants.

Infected plants should be pulled, bagged and disposed of. Do not compost. The area should not be replanted with susceptible impatiens species, but can be replanted with any other plants. Fungicide sprays are not recommended in landscapes and home gardens! It is expected that IDM will be a recurring problem. Impatiens downy mildew oospores from infected plants overwinter in the soil and IDM can infect wild impatiens (jewelweed, I. capensis). A comprehensive fact sheet is available at: -Tina Smith, UMass Extension"


Follow-Up Postings:

RE: UMass Extension Landscape Message May 17, 2013

Thanks Claire. I have really appreciated this service you have been providing this forum for years. But every time I see that you have posted an update from UMASS, I always have this feeling of dread before clicking. What will be the bad news? Perhaps some horrible news about winter moth, or the Asian long-horned beetle, the ash borer, instant oak death or god only knows what else!

RE: UMass Extension Landscape Message May 17, 2013

  • Posted by claire z6b Coastal MA (My Page) on
    Fri, May 17, 13 at 18:33

The UMass people do seem to report unpleasant happenings, which I guess is the reason for the report in the first place - to give professionals a heads-up for problems they may need to deal with.

I just went back to the Landscape Message to see if I could find any good news and I did find this:

"Metro West (Acton):

General Conditions: Finally, it rained! The area received 0.83” of rain and gained 61 GDD during this recording period".

A little something cheerful, anyway.


RE: UMass Extension Landscape Message May 17, 2013

I love reading it also, but it's sort of like watching a train wreck! I love it all though, so interesting. Thanks for posting it, Claire.

I heard from a friend that their nursery said to skip the impatients this year because of this. I usually plant at least a flat. I'm a little excited to be forced into some variety.

RE: UMass Extension Landscape Message May 17, 2013

Yup. No impatients for me this year either. So sad. They were so easy to grow. But I find begonias even more versatile. I have some planters very close together and one gets no sun and one gets lots of sun. And I like them to have similar begonias are my go to plant....thriving and flowering in full sun and no sun.

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