Monday, November 1, 2021

Sweetgrass - Purple in the Fall


Horticulture Hotline 11/01/21

By Bill Lamson-Scribner


Question: Bill, I have a white, sticky, fuzzy fungus on my Sweetgrass plant. What can I do? I am retired now and my wife expects me to help her keep a nice yard when I’m not fishing or emailing jokes to my friends.


Answer: Congratulations on your retirement! Good luck with your fishing!


The purple of the sweetgrass plant is looking lovely right now throughout the Lowcountry. Another sign of fall – oysters anyone?


Your Sweetgrass plant most likely has a soft body, sucking bug called a mealy bug attacking it. Mealybugs are like aphids, scale, white flies, the “nasty rascal, the chinch bug”, lace bug and other sucking bugs in that they suck plant juices or sap from the host plant.


I was surprised when I first saw mealybugs on Sweetgrass. I usually associate mealybugs with plants grown inside buildings, homes (interior plantscapes) or greenhouses. I usually think of ornamental grasses as being pest free – wrong!


As with any sucking bug, you want to get the situation under control fast, or you will have the secondary problem that looks way worse than the fuzzy, airy mealybugs. The secondary problem is the dreaded sooty mold.


Sooty mold is the black mold that grows on the excrement (poop) of certain sucking bugs. Have you ever seen a black gardenia (from white fly poop) or crepe myrtle (from aphid poop)? Certain insects have a very short digestive track and they are drinking sap from a plant that is pressurized. The sap goes in their mouth and out their behind very rapidly covering the plant with a sugary substance (often called honey dew) that this mold grows.


In human terms, if you could connect your mouth to, let’s say, a keg of beer or maybe a soft serve ice cream machine at some point the beer or ice cream would be coming out of somewhere (nose, ears, …) leaving a mess. Insects have hardly any digestive tract to slow things down.


A very effective way to control these mealybugs, while not hurting the beneficial insects, is to use an insecticidal soap. Also drench the area around the Sweetgrass with Dominion.

Dominion is a long-term systemic insecticide that will free you up for more time fishing.  


Large Patch Fungus is really active. Fall Army Worms are still very active. Rats, roaches, mole crickets and fire ants thrive in the fall. It is a good time to apply Neem Oil or Horticulture oil for over wintering insects.


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