Geraniums are moderately low-maintenance plants as long as they receive enough sunlight and water and are planted in well-draining soil. Geraniums can become infested with pests even though their growing requirements are met. Pests such as aphids, whiteflies, cotton cushion scales and spider mites eat away at foliage. Healthy geraniums may withstand most pest damage, but it is important to treat the geranium to avoid a decline in plant health.
Aphids quickly reproduce in the spring. What may seem like a moderate aphid problem on your geranium plant can turn into a full-blown infestation within a few weeks. Pests can reproduce at a rate of 80 offspring a week, according to the University of California. Gardeners can tell aphids have been sucking up nutrients from their geranium leaves by looking for yellowing leaves, leaf curl and defoliation. Treat aphids with an insecticidal soap. Insecticidal soap will have to be reapplied because it is effective for only 24 hours.
Whiteflies are tiny insects found underneath the leaves of geraniums. Like aphids, these pests suck up nutrients from leaves. In addition, whiteflies leave behind a sticky substance called honeydew, which can catch fungal spores floating through the wind. Some of these fungal spores such as sooty mould may cause a fungal disease. Gardeners can repel whiteflies by placing aluminium-coated construction paper around geranium plants. Spray the plant with insecticidal soap to remove sooty mould and apply reflective mulch around the plant.
Cottony Cushion Scales
Cottony cushion scales can be orange, brown or yellow. They get their name because of their large egg sac that holds more than 800 red eggs. These pests suck phloem sap out of geranium's leaves, which can cause defoliation. Geraniums lacking leaves may suffer from nutrient loss. Scales are hard to control with insecticides, according to the University of California. Their egg sac protects their bodies from toxins in pesticides. Gardeners may treat cottony cushion scales by placing double-sided tape around the geranium's container or on mulch around the plant to trap the pests.
Gardeners may notice spider mite webs before seeing the tiny insects themselves. Spider mites reproduce at an alarming rate during hot weather. Mites suck out the cell contents of leaves, which causes the plant to turn bronze or yellow and defoliate. Plants that are water-stressed receive the worse damage, according to the University of California. Avoid spraying any insecticide that contains carbaryl. Carbaryl actually causes spider mites to reproduce at a faster rate. Use insecticidal soap applications to control your spider mite infestation.
- University of California Agriculture and Natural Resources; Cottony Cushion Scale; E. E. Grafton-Cardwell; December 2003
- University of California Agriculture and Natural Resources; Whiteflies Management; M.L. Flint; September 2002
- University of California Agriculture and Natural Sciences; Spider Mite Management; M.L Flint; January 2000
- University of California Agriculture and Natural Resources: How to Manage Pests: Geranium