If you’ve noticed that your plants that have aphids on them seem to have more ants than usual, it’s no coincidence at all. This is because aphids and ants can form a strange dependence on each other.
Aphids are common vegetable garden pests that can survive a large range of temperatures; warm but not hot temperatures are preferred. They are quite tiny being only about 1-7 mm long but can be seen with the naked eye. If you aren’t familiar with what they look like their tiny size makes it almost impossible to notice them until you have a full-on infestation and your plant is visibly damaged.
It can be quite puzzling to realize why your vegetable plant leaves are turning yellow during an aphid infestation if you are unable to see the aphids. The yellowing of leaves caused by their feeding can look very similar to yellowing caused by nutrient deficiencies, over-watering, under-watering, or even a virus.
Knowing how aphids feed on plants can make it a little easier to identify the damage done. Aphids have mouthparts that can pierce plant tissue to suck out plant sap. Their feeding behavior results in a mottled or blotted yellowing pattern. The areas that they have sucked out plant sap from turn yellow while smaller areas that they have missed remain green, with the entire leaf turning yellow eventually.
Plant sap is composed mostly of sugars. Aphids consume part of these sugars but secrete a waste product that is still full of sugars. The waste substance that they produce is commonly called ‘honeydew’ due to its sticky nature and light brown color. Honeydew is not only secreted by aphids but also by scale insects, whiteflies, mealy bugs, and other pest insects that feed on plant sap.
Since honeydew is full of sugars it has a high nutritional value. Here’s where the ants come into the story. Ants consume the honeydew produced by aphids. Not only do they consume it but ants actually ‘farm’ aphids in a similar way that we farm cows for milk. Since ants are usually much larger than aphids, they protect the aphids from predators and can carry them back to the plant if they fall off.
This has two different implications for vegetable gardeners:
1. Ants make it easier to notice that there are aphids feeding on your plants
It’s quite unlikely that you are going to find aphids on leaves that have already turned significantly yellow. This is because a leaf may turn yellow only a day or so after aphids have been feeding on it. By this time, it’s quite likely that aphids would have already moved away from this leaf and have already started feeding on another leaf.
Ants are a bit different. They feed on the honeydew produced by the aphid as it is secreted and for this reason, can be found gathered around clusters of aphids while they feed. Ants are usually a bit larger and can be easily seen on a plant. If you see ants clustered on a leaf or around a stem, if you look closer you’re quite likely to notice aphids.
Aphids, even of the same species, can be of different colors ranging from green/peach to darker green/black depending on their life stage. Aphids usually take the color of the leaves that they are on resulting in being camouflaged but ants are usually black, brown, or reddish and are more easily visible.
In addition, ants can point out aphids that have just started feeding on that particular area of the plant and can be removed before they fully damage the plant. Even though their feeding alone can badly damage a plant if left untreated, the biggest problem is that they transmit viruses as they feed on plants. This means that it’s best to get rid of aphids asap.
2. Ants make it harder to get rid of aphids
Although ants are a good indicator of aphids they can make getting rid of aphids tough. Ants protect the aphids as they act as a food source for the ants, which makes it hard for ladybugs and other predators of aphids to get close to them.
One of the best ways to get rid of aphids naturally is to knock them off the plant using a strong stream of water. Even though aphids move quite a bit it’s rather unlikely that they will be able to climb back up the plant by themselves once they have been knocked off the plant. This is where ants interfere. Ants will usually carry these aphids back up the plant, where they can start working for the ants once again.
This means that if there are ants protecting aphids on your plants, you’ll first need to get rid of the ants before getting rid of the aphids. This can be done naturally without affecting the plant by sprinkling chili or hot pepper powder on the plant. Smaller types of ants may be killed by the chili/hot pepper power but the chili powder can only repel larger types of ants. You’ll have to treat the plant every two days or so using the chili/hot pepper powder until there are fewer ants around before trying to knock off the aphids. Once you have gotten rid of the ants and have reduced the number of aphids that are on the plant, natural predators will be able to get to work and get rid of the balance aphids.
So the next time you see your leaves turning yellow and ants running all over, it could quite possibly be that you have an aphid infestation on your hands. Let the ants guide you toward the aphids.