Pests, diseases negatively affect daylily appearance
By Brenda Heinold – Victoria County Master Gardener
Apr 30, 2017
PHOTO CONTRIBUTED BY BRENDA HEINOLD/VICTORIA COUNTY MASTER GARDENER
View the beautiful display of daylilies at the Master Gardener Victoria Educational Gardens currently in full bloom and always open to the public. Care is taken to keep them pest- and disease-free.
PHOTO CONTRIBUTED BY BRENDA HEINOLD/VICTORIA COUNTY MASTER GARDENER
Daylily aphids with piercing and sucking mouth parts are microscopic in size. They often infest the plant between leaves in the early spring and feed internally. Shown here are daylily aphid cast-off exoskeletons on daylily buds.
PHOTO CONTRIBUTED BY LARRY BARNES/DEPARTMENT OF PLANT PATHOLOGY, TAMU
Daylily rust is evident by the formation of orange pustules on the underside of a leaf. Although it usually does not kill the plant, it can spread rapidly from one daylily to another, weakening them and making the unsightly.
Daylilies with thousands of cultivars in a rainbow of colors have been called the perfect perennial because of their adaptability to a wide variety of growing conditions.
Easy maintenance
They are easy to manage and usually require little beyond a sunny location, adequate water and occasional fertilizer. They multiply readily and lend many years of beauty to wherever they are planted.
Can have pests – don’t kill plant; can affect appearance
Nevertheless, they are not completely free of pests and diseases. Although those pests and diseases rarely kill the plant, they can negatively affect the appearance of the flowers and foliage. Fortunately, the home gardener has some fairly simple solutions to maintain the daylily’s beauty.
Pests that affect daylilies are seasonal and change with temperatures.
Aphids in early spring
Early spring sometimes brings an infestation of aphids to our daylily beds. The daylily aphid (Myzus hemerocallis) is a small, white to green, soft-bodied insect with piercing and sucking mouth parts. Although the daylily aphid is specific to daylilies and does not infest other plants, daylilies can be attacked by other types of aphids.
The daylily aphid most often appears in early spring and begins sucking sap from between the leaves of the daylily. The fan structure of the daylily means that the aphids might be difficult to spot, the first sign often being some yellowing leaves or deformed buds.
Small white specks may appear on the leaves and even on the scapes and buds. These small white specks, resembling a light smattering of white cornmeal are the cast-off exoskeleton of the aphid. If you see them, your daylilies have aphids.
Thrips in late spring/early summer
After the weather warms up, thrips can become a problem on daylilies. Thrips are extremely small insects, usually less than 1/16 inch long. To spot these tiny pests, hold a sheet of white paper under a daylily leaf or flower and then strike or shake the plant. You should see some debris on the paper. Examine it in bright sunlight. If any of the specks move, then you might have thrips.
Spider mites in hot summer
As we move into really hot weather, watch your daylilies for signs of spider mites. Because spider mites are extremely small, they often go undetected until yellow spots appear on the leaves or flowers. To determine if you have spider mites, use the same “white paper” method that you used to investigate thrips.
See adjoining information on how best to treat these three daylily pests.
Fungus affects foliage
Fungus can be equally as symptomatic and detrimental to daylilies, negatively affecting foliage.
Daylily rust – forms orange pustules on underside
Daylily rust (Puccinia hemerocallidis), a fungus that produces yellowish water spots on leaves, followed by progressive yellow and brown spots and streaks, can negatively affect the beauty of daylily foliage. It can spread rapidly from one daylily to another, weakening them and making them unsightly.
Aphids and daylily streak can also cause yellow spots and streaks, but a distinctive feature of daylily rust is the formation of orange pustules on the underside of the leaf. To test for daylily rust, run a white tissue along the underside of the affected leaf. The tissue will be stained orange if rust is present.
Because daylily rust rarely kills a plant, you could choose to do nothing. But few of us can stand by and watch our beautiful daylily foliage become yellow and withered. If you choose to take action, use a contact fungicide such as one containing chlorothalonil or mancozeb at the first sign of the rust. Follow up with a systemic fungicide. Read and follow the label directions carefully. Also, remove and dispose of affected leaves.
Daylily leaf streak – develops yellow and brown streaks/spots
Like daylily rust, daylily leaf streak is caused by a fungus, Aureobasidium microstictum. Symptoms begin at the leaf tip with a yellowing of the mid-vein. As the fungus progresses, the leaves develop yellow and brown streaks and spots. The leaves will wither and die.
To avoid leaf streak, be sure to clean up and discard dead foliage and to avoid overhead watering. To control leaf streak, spray the affected daylily with a fungicide containing thiophanate-methyl or myclobutanil. Spray three or four times at two-week intervals.
A quick search of the internet can provide more advice on the detection and management of both daylily rust and daylily leaf streak.
The Gardeners’ Dirt is written by members of the Victoria County Master Gardener Association, an educational outreach of Texas A&M AgriLife Extension – Victoria County.
TIPS FOR TREATING DISEASES
• Clean up and discard debris around plants.
• Try working horticultural cornmeal around plants.
Don’t overwater – can spread disease.
DAYLILY RUST
• Use contact fungicide containing chlorothalonil or mancozeb at first sign.
• Follow up with a systemic fungicide.
Remove and dispose of affected leaves.
DAYLILY LEAF STREAK
• Avoid overhead watering; discard dead foliage.
• To control, spray affected daylily with fungicide containing thiophanate-methyl or myclobutanil.
Spray three or four times at two-week intervals.
• NOTE: Always use least toxic control method first. As with all insecticides, follow label’s directions and precautions carefully.
TIPS FOR TREATING PESTS
DAYLILY APHIDS
• With internal feeding and damage by aphids, first allow natural predators to keep numbers down (green lacewings, ladybugs, and parasitic wasps).
With more severe infestation, use insecticide containing bifenthrin, cyfluthrin or permethrin.
THRIPS
• First allow natural predators like above.
With more severe infestation, use systemic insecticide containing acephate.
SPIDER MITES
• Try horticultural soap or citrus oil spray.
• Use insecticide containing bifenthrin.
• To address recurrence, keep beds clean of debris and weeds that spider mites may overwinter.
PESTS/DISEASES THAT CAN AFFECT DAYLILIES
SPECIFIC PESTS
• Daylily Aphids
• Thrips
Spider mites
Others
• Slugs
• Snails
Deer
Diseases
• Daylily rust
• Leaf streak
• Crown rot
Please find other daylily info, articles, photos, videos HERE!