Are your roses sporting new leaves that glisten in the sunlight and are slightly sticky to the touch? See a trail of ants crawling up the trunk of your plum tree? How about powdery black stuff on your camellia bush or the garden furniture next to it? All are indicators that sucking insects may have arrived and need your attention.
There’s a group of soft-bodied insects — aphids, mealybugs, soft scale, and whiteflies being the most common, that feed by sucking juices from plants. The direct damage they inflict on the plant can cause spotted, bleached, or curled foliage, and stunted growth. Indirect damage comes from the waste they produce. The pests can’t utilize all the sugar in the rich sap they draw from the plant, and excrete the excess in the form of honeydew, that looks just like drops of honey on foliage. When pest populations build-up, the sticky honeydew can drip from one part of the plant to another, or to anything around it — other plants, walls, walkways and more.
And if that wasn’t bad enough, that honeydew provides the perfect growth medium for sooty mold, a black or dark gray coating on the surface of the plant leaves and stems (or other non-living surfaces). This unsightly fungus doesn’t attack plants directly but can weaken them. Then, there are the ants. They love honeydew and will fiercely protect those soft-bodied producers, especially aphids, from predators, in order to keep that sugary stuff coming.
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If you do find sooty mold (and have removed the source of honeydew), it will gradually weather away, or can be washed off with a strong stream of water or soap and water.