You figure once you bring your houseplants in from the outside for the winter, especially if you don’t see any pests on the leaves, you are probably pest free. However, that was not the case for a homeowner that had brought in some potted geraniums during fall. In November, she noticed some chewed leaves and droppings on the foliage one of the plants (the others were uninfested). This prompted a closer inspection of the plant which led to the discovery of a caterpillar.
Photo 2: Chewing damage on geranium. Jeff Hahn
After some investigation, the caterpillar appears to be a tobacco budworm. These insects are not native to Minnesota but are occasionally found in gardens during late summer after they have ridden air currents up from the south. (see Yard and Garden News, September 1, 2007. They would not survive our winters outdoors but this individual received a reprieve when it was brought indoors. It presumably was hiding in the soil escaping detection.
Further investigation did not turn up any additional caterpillars. Physical control was the only necessary action that was needed in this case. This is not a common insect in Minnesota and the amount of injury it caused was minor. The lesson here is to continue to monitor your houseplants for pests not only in the fall after you have brought them indoors, but periodically throughout the winter for any problems that may have been missed.