The yellow iris is a perennial member of the iris genus. Its scientific name, Iris pseudacorus, refers to the similar appearance its leaves bear to Acorus calamus, the sweet flag plant. Native to parts of Asia, Africa and Europe, this bright yellow flower proves to be enticing to gardeners and pests, a number of which will eat the foliage of these blooming beauties. The pests that affect the yellow iris are not exclusive to this plant and will generally eat any member of the iris family they come across.
The larva of the Macronoctua onusta moth is also known as an "iris borer." These pests have a range as far north as the Canadian border and as far south as Tennessee. They begin eating iris foliage in the early spring until the end of summer. Iris borers will begin eating the outer leaves first, working their way toward the center of the plant. Eventually, the caterpillars will burrow into the main stalk of the flower, eating their way through the plant.
Orthacheta Bud Fly
The larvae of this pesky insect love to feed on the pollen of irises. The larvae resemble small, white maggots. They bore into the buds of the yellow iris and feast upon the pollen inside. When the iris blooms, the flowers will be deformed and marred. The Orthacheta bud fly larvae burrow into the stem of the Iris to safely await the transformation into an adult.
Although many of the plants that feed on the yellow iris are insects, the vole is a notable exception. A vole is a small, mouselike creature that nibbles on plant roots and stems. Voles travel in underground networks, occasionally coming to the surface. Their tunneling abilities make it easy for them to eat the roots of the yellow iris without ever being seen. Pest control measures work to control them, but if you're squeamish about this, hot pepper sauce will prevent voles from snacking on your irises.
Nematodes are tricky to classify and even trickier to control. There are good nematodes and bad nematodes. Technically, nematodes are microscopic organisms that live in the soil. Because they are so hard to see, many gardeners and resources consider them a disease rather than a parasite. A common example of nematodes are roundworms, which suck the juices from the roots of iris plants. Over-watered irises, as well as those that have been exposed to a drought-flood situation, are more prone to nematode damage than irises that have been watered moderately at regular intervals.