Aphids, spider mites, and your plants
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About one month ago, I gave my Rockroses some fertilizer. They dropped the buds and shed about 30% of their leaves. I added ashes to lower the pH, but they continue to decline. The plants are about 11 years old. Any thoughts?
A very experienced Master Gardener that I consulted told me that Rockroses are native plants that don’t need fertilizer, nor do they require a lower pH soil. They like our alkaline soil. She also said that the average Rockrose plant only lives a few years, so eleven year old plants are quite uncommon. You might consider digging up the old plants, adding some compost, and planting new plants later in the fall. It is too hot now for good root growth.
For those of us who are unfamiliar with Rockroses (me), I also consulted Native Texas Plants by Sally and Andy Wasowski. I learned that Rockrose or Pavonia is classified as a shrub, as it has a woody base and branches like a shrub. It doesn’t die back in the winter, unless it is unusually cold. It reproduces freely by seed. You should let a few seedlings survive each year to replace the mother plant, which has a short life span. The flowers are clear pink, numerous, open in the morning, and close in the afternoon. If desired, you can prune your Rockrose any time from February to October.
What is the dark, sticky substance on my black-eyes peas?
It sounds like aphids have infested your plants. A heavy infestation can cause distorted growth, reduced growth, poor quality, lower yield, and can even kill the plants. The insects suck the sap out of the tender plants, shoots, and leaves. They secrete a sugary substance called honeydew, which attracts a dark fungus called sooty mold. This fungus is unsightly and stresses the plant by reducing the amount of sunlight reaching the leaves.
Sometimes, a heavy blast of water from the hose will knock the aphids off the plants. You can also spray them with insecticidal soap. Please know that more than one application will be needed. Once the honeydew-producing insects are suppressed, the sooty mold will gradually weather away. The sooty mold does not cause the black-eyed peas to be inedible. Just wash them with a solution of a mild soap and warm water before shelling them.
My trailing rosemary and Lantana plants are about 2 years old and historically very healthy. Recently, the Lantana has failed to flower and has mottled leaves. The rosemary is less full and looks rather dry, even though I have it on a drip irrigation system. I have noticed some webs on the rosemary, but no spiders. Any ideas?
I suspect that you might have spider mites on your rosemary. Spider mites are very small -- about the size of the period at the end of this sentence. Use a hose- end sprayer filled with water and a squirt of dish soap and spray the plants every few days.
Most likely, your Lantana is resting and you don’t need to do anything. My friend has several plants in his yard, and they have the same symptoms that yours have. Closely inspect the old blooms that are browning, and you’ll probably find some seeds. I expect the Lantana will bloom again later this fall.
Penny Wallace is a Texas Master Gardener with Texas A&M AgriLife Extension. If you have a question to be answered, call the Master Gardeners at 830-379-1972 or leave a message to be answered. The website is guadalupecountymastergardeners.org. The Master Gardener research library is open Mondays from 8:30 to noon, at 210 East Live Oak Street in Seguin.