We were talking on the radio this past week about Indian
Hawthorn and the disease they
get, so I figured I would expand on this topic this morning,
since this plant is so common in the Lowcountry.
The Indian Hawthorn or Raphiolepis have been plagued with
leaf spot for years now. It seems like
right after the Red Tips (Photinia) were virtually wiped out by entomosporium
leaf spot, the diseased began attacking the Indian Hawthorn. Indian Hawthorn and Red Tips are in the same
plant family as roses (Rosaceae).
When dealing with a plant that is very susceptible to a leaf
spot disease I like to think of several different factors:
·
Is this plant worth keeping in the landscape or
should I replace it with another plant that is not susceptible to disease.
·
Is this plant worth spraying ever 14 – 28 days
to keep it in my landscape? To keep an Indian
Hawthorn alive, it needs a life-support system.
The plant must be sprayed at least monthly or it will get leaf spot
again.
·
What cultural practices can I do to help relieve
the pressure of the disease? The removal
of fallen foliage (sanitation) is key when dealing with a leaf spot
disease. Having a healthy soil, as
determined by a soil test, is also very important because a stressed plant is
more susceptible to disease. Providing
the correct amount of water preferably through a drip system, so the plants are
not over-watered or drought stressed.
Proper fertility as determined by the soil test is also important. Use nitrogen fertilizer very sparingly in
small amounts because flushes of new growth are more susceptible to leaf
spot. Choose “resistant” varieties such
as “Olivia”. This does not mean that
this plant will never get this disease; it is just more resistant to the
disease. Mulch like Cotton Burr Compost will help prevent splashes of water
drops that could spread the disease. Also
this mulch will lower the watering needs of the plants. Bioscience products
like Messenger should be considered as well. Messenger will thicken the cuticle
of the leaf making more resistant to the disease as well as more drought
resistant. Good air movement.
·
What control products will work best on this
disease? If you decide to spray, be
prepared to spray often. Honor Guard,
Banner, Dithane (Mancozeb), and Kocide are good choices. These products should
be used in rotation and according to label. I like the lime-sulphur idea or
lime-copper spray for the reason that the original Lamson–Scribner invented
this product in an effort to save the French wine crop in the late 1800’s. He
called it Bordeaux
mix. When spraying these chemicals, an appropriate surfactant should be used.
Certain surfactants work better than others with particular products.
I’m in yards all the time and this
disease is the most common disease I see in our Lowcountry landscape. I usually
recommend replanting the area. I can understand spraying roses all the time.
Indian Hawthorn – ah, not so much.
