Geraniums are sturdy plants with bountiful blooms, but those blooms can quickly be destroyed by an attack of tobacco worms or aphids. Tobacco worms in particular have caused such severe damage that in some parts of the United States where the tobacco worm, nicknamed the "geranium budworm," is prevalent, many gardeners have given up planting geraniums altogether. Don't let this discourage you. By following some simple steps, you can keep pests from your geranium plants.
Spray your geranium plants down with insecticidal soap, available under many brand names at any garden centre. When spraying your plants, be sure to spray the underside of the leaves as well as the tops.
Spray geranium plants with Sun Spray Oil, an organic spray available at any garden centre. Sun Spray Oil smothers geranium pests such as aphids, mealy bugs and white flies. Make sure to do this in the evening.
Release garden predators such as ladybirds on your geraniums. You can purchase ladybirds at your local outdoor superstore. Ladybirds are effective against the majority of geranium pests, including tobacco worms, aphids, caterpillars, white flies and cabbage loopers.
Spray tobacco worms and caterpillars with Bacillus thuringiensis, an insecticide available at all garden centres. Spray the plants in the evening when the caterpillars and tobacco worms are active, handpicking and disposing of any pests that you see on the plant. This insecticide will kill geranium pests without killing your garden predators.
Turn over your garden soil with a garden claw between freezes during the winter to kill any underground pupae, ensuring a pest-free start for your geraniums in the spring.
Tobacco worms' colours vary depending on the colour of their host flower, but they are easily identified by the two pale stripes running parallel down the length of their entire body. They can be red, green, tan or brown.
Do not use Sun Spray Oil during the heat of the day, as the combination of the sun and the oil can cause the leaves of your geranium to burn.