I was scouting one of my community gardens last week, when I was bombarded by a massive aphid population boom on my kale. Dozens of aphid clusters were evident on the undersides of most of my kale. You could even see the aphids start to spread to the next crop, the cabbages. On two of the cabbages, I noticed the aphids more densely covered the undersides of the leaves. In combination, a large quantity of fire ants were present as well and looked like they were going crazy, moving rapidly among the aphids. Contrary to my first impression, the ants were not harming the aphids in any way but farming them. Yes, farming them. Recall that aphids are a piercing and sucking insect [Figure 1 depicts their labium], and that they secrete a high sugar, nectar like, liquid. As a result, ants farm aphids by herding them close together, and then collect the sweet liquid the aphids secrete for food. (https://www.sciencedaily.com/releases/2007/10/071009212548.htm). Figure 2 shows ants farming aphids, while Figure 3 shows an ant consuming an aphid’s secretion.
Fig 1 Fig 2 Fig 3
How did I get rid of all the aphids? I want to prevent using highly toxic compounds in my gardens, so because I scouted and caught the issue early, I simply used soapy water to kill the aphids. To make the solution, simply mix one gallon of water with 1-2 tablespoon of everyday dish soap. Then, using a small sprayer, and spray both the top and bottom of the leaves. Although, this is a great low toxic solution for killing pests, be warned that this will kill all soft bodied bugs including beneficials like ladybugs. Also, use the solution in moderation; no more than once a week. This solution will not harm your plants but it can strip away the protective waxy coating on its leaves.