Geraniums are popular flowers for annual bedding plants, pots, window boxes and hanging baskets. Unfortunately, a number of caterpillars thrive on geraniums and cause significant damage. The caterpillars are the larvae of various types of moths. Tobacco budworms, cabbage loopers and fall cankerworms are common caterpillars that feed on geraniums.
Tobacco budworm caterpillars feed on geranium flower buds and petals. The buds do not open or the flowers have chewed and ragged edges. Tobacco budworms are yellowish to yellowish-green in color and have many black thorn-like spines. They grow to a length of 1.5 inches. The caterpillars are most active at dusk.
The dusky white to pale green caterpillars have a white stripe along their sides. The 2-inch caterpillars feed on geranium leaves for about four weeks before developing into the pupa stage. They leave a large amount of sticky, wet fecal material on leaves and move in a looping motion.
The light green to dark brownish-green caterpillars have white lines along the body. They are 1-inch long and spend about four weeks feeding on geranium leaves before maturing.