Daylily leafminers are an invasive pest that was introduced to the US around 2006 from Taiwan and Japan. The adult is a small black fly and the larvae are pale-yellow, feeding in the ribs of leaf tissue. When infested, these leaf-mining pests create whitish mines that remain visible on the plant’s leaves. The adult leaves a white or yellowish odor. The pest overwinters in small, tan pupae that overwinter near the base of the plant’s leaves.
While this pest is difficult to detect, it may be present in small numbers. Symptoms of this pest infestation may go unnoticed until the plants are damaged. To determine if you have a thrips problem, you can use a stiff piece of paper and strike it against a part of your daylily plant. Remove the paper and examine it under bright sunlight. If there are thrips present, they will move across the paper.
To prevent the spread of this disease, be sure to remove infected leaves immediately. You can apply fungicides to prevent the spread of the disease by protecting susceptible new growth from infection. It is best to spray three to four times at two-week intervals. Ladybug daylilies are susceptible to daylily leaf streaks, but disease-resistant cultivars are available that can be used on your daylilies.
Ladybug daylilies are tetraploid, semi-evergreen perennial plants with grass-like foliage and a scape that grows 12 to 36 inches tall. The flower is the width of a man’s hand and can have one or more petals. It can also be solid or multicolored.