There are hundreds of petunia varieties. According to the University of Minnesota, they rank among the most popular flowering annuals. They may be part of your flower garden, or kept in a flower box on your windowsill. Petunias are low-lying and have a diversity of brilliant colors and attractive foliage. They bloom all summer with little maintenance and continue to be one of the most durable and long-seasoned blooming plants. Although petunias are not often troubled by pests, you might need to take steps against aphids, flea beetles and slugs that will occasionally attack.
Since bugs don't often bother petunia plants, your first approach is hand-picking. If your bug infestation isn't too large, this should work fine. Pick off any bugs you see and remove dead blooms that may attract them.
If your bug problem is too big to pick them off by hand, try to blast them with a water hose. Keep the pressure of the spray at the level of a hard rain.
Spray your plants with a mixture of liquid soap and water. This insecticidal soap solution will kill any bugs still hanging on.
As an added deterrent, you can mix up a garlic solution. Finely chop 10 cloves of garlic. Let them soak in mineral oil for 24 hours. Strain and mix with water in a spray bottle. Add a couple drops of the liquid soap and spray on the plants. The garlic and soap combination should take care of any pests that remain and repel others.
As a last resort, you could purchase a chemical pesticide. One popular choice is Nicotine sulphate 40 percent solution. There are others available, such as malathion, but the adverse effects to the environment might be a concern. Check at your gardening store for the best recommendation and proper use. Regardless of the choice you make, be sure to follow the instructions that come with the product.