Do You Have Ants on Your Plants?
Most of the insects that you see around your home are neither pests nor beneficial. For the most part ants can be put into the category of not doing any harm to the landscape. However, the presence of ants may indicate that another pest is feeding on your plants.
Aphids, or plant lice, are small insects that feed on new shoots of a wide variety of plants. I have found them feeding on maples, roses and cucumbers this year. Aphids suck sap out of a plant and, if they build up to large enough numbers, they can damage the area that they are feeding on.
Aphids give off a substance called honeydew that is a sweet, sticky substance. Honeydew is used as food by ants, so you will often find ants mingling among aphid colonies. In fact, certain types of ants and aphids have a symbiotic relationship. In return for the honeydew, ants will protect the aphid colony from predators like lady beetles. Some ant species will even take aphid eggs to their nest to protect them from winter weather.
So, if you are seeing ants roaming around on your plants, take the time to see where they are going. Ants will often lead you to the aphid colonies that may be damaging your plant.
Another indicator that you have aphids is the leaves on the plant will begin to turn black. The black substance is called sooty mold, and it is growing on leaves that have been coated with honeydew. Sooty mold does not infect the plant, but it can block sunlight from getting to leaves.
There are a number of insecticides that are effective in controlling aphids. Insecticidal soaps and horticultural oils are an option if you are into organic gardening.