Horticulture Hotline 12/02/19
By Bill Lamson-Scribner
Yes, once again, it is time for The Holiday Festival of
Lights at James Island County Park. I know many of you are new to the area.
This is a “must do” event. I have been to many other light shows and none of
them have even come close. You have to experience it for yourself!
The grass is going dormant and the insects are moving
deeper, so once again (do they ever slow down), the moles are very visible.
Stop by a Possum’s for the three prone approach handout for the best results at
controlling this pesky mammal.
After all these years, the Indian Hawthorn, Raphs or
Raphiolepis have been really suffering. Raphs have been plagued with leaf spot
for years, and I’m always surprised to see them in a landscape especially a
newer one. 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:
1. Is
this plant worth keeping in the landscape or should I replace it with another
plant that is not susceptible to disease.
2. 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.
3. 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. If I was planting something new, I would
stay away from any of the Raphiolepis plants and use something proven to be a
little less maintenance. 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 KeyPlex should be considered. KeyPlex
will thicken the cuticle of the leaf making more resistant to the disease as
well as more drought resistant. Pruning for good air movement.
4. 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-sulfur 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 (unfortunately Bordeaux mix is not available anymore). 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.
Always read, understand and follow product label. The
product label is a Federal Law.
Bill Lamson-Scribner
can be reached during the week at Possum’s Landscape and Pest Control Supply.
Possum’s has three locations 481
Long Point Rd in Mt. Pleasant
(971-9601), 3325 Business Circle
in North Charleston
(760-2600), or 606 Dupont Rd,
in Charleston
(766-1511). Bring your questions to a Possum’s location, or visit us at
http://www.possumsupply.com. You can also call in your questions to “ The
Garden Clinic”, Saturdays from noon to 1:00, on 1250 WTMA (The Big Talker). The Horticulture Hotline is
available 24 / 7 at possumsupply.com.
