Streaks On Daylily Leaves: Learn About Daylily Leaf Streak Disease

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By: Tonya Barnett, (Author of FRESHCUTKY)

Daylily plants are among one of the most popular perennial landscapingflowers in the United States, and for good reason. Their disease resistance andhardy vigor allows them to thrive in a diverse set of growing conditions.Whether grown in full sun or partial shade, daylily plants will rewardhomeowners with a profusion of large blooms and glossy green foliage throughoutthe entire growing season.

While robust, there are some issues that may cause theseplants to struggle in the garden. Daylily leaf streak, for instance, can causedistress for both growers and daylily plants.

What is Daylily Leaf Streak?

When daylily leaf streak presents itself, the fungus Aureobasidium microstictum has infectedthe plant. Daylilies with leaf streak may initially show very little signs ofinfection. However, upon closer inspection, growers may first begin to noticeyellowing of the plant’s leaves along the midrib.

As the disease progresses, the streaks on daylily leaveswill begin to darken and turn brown. These brown streaks will eventually causethe individual leaf to die back. While most infections will not cause theentire plant to die, daylilies with leaf streak may lose several leavesthroughout the course of the season.

Controlling Daylily Leaf Streak Fungus

Streaks on daylily leaves most commonly begin during periodsof hot and wet weather. This is when conditions are ideal for fungal spores tobe released. Since this fungus is known to overwinter in the garden in debrisfrom previous seasons, garden cleanup is a key aspect of prevention.

The leaves of daylilies with leaf streak should beimmediately removed from the plant and destroyed. In addition to this maintenancepractice, growers should always avoid wetting the leaves when watering. Sincefungal spores often spread through wet environments and splashes of water, thiswill help prevent further spread.

If streaks on daylily leaves become a consistent yearly issue,the use of fungicides is an option. As always, make certain to follow labelinstructions carefully. If treating with fungicide, the product should only beused when conditions are optimal for the fungal disease to begin.

If planning to add more daylilies to the garden, you canchoose varieties specifically resistant to daylily leaf streak. With a fewsimple steps, controlling daylily leaf streak and preventing its spread canhelp ensure beautiful plants all summer long.

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Neem for daylily leaf streak?

Has anyone ever treated leaf streak successfully with neem oil? I applied some earlier this week, and will probably apply once more. Not sure how long it takes to see improvement.

I was not aware neem was an option for treating leaf streak, please let us know if you have any success!

Neem oil does have some fungicidal properties but I also am not aware if it controls daylily leaf streak. I do know it controls rust on daylilies. Please do keep us informed.

I know spacing out the daylilies to allow for more air movement as well as not over watering the foliage help to reduce the disease from a cultural management perspective.

Daconil is a pretty effective fungicide sprayed at 7-10 day intervals if already disease is present. Also infected leaves can be removed.

I have not tried Neem, but I do use a mixture of Daconil and Immunox, so far I can't tell it has made any difference with rust or leaf streak. I plucked so many leaves off the Daylilies they are pathetic looking as far as the foliage is concerned and still the new leaves continue to get rust and leaf streak. I have been spraying all year, but with so much rain I can not say this is a fair trial, because often the spray does not get to stay on the foliage for long.

My report three weeks out: I sprayed three times and have let them be. It's been very dry here. Most of the leaf streak is gone. Only two plants had a new streak, but look healthy. I can't really say whether the neem helped. Does leaf streak ever clear up without chemical

Leaf streak occurs when the environmental conditions are favorable. But once it gets started it is very difficult to manage, even with chemicals. The conditions for its growth can become unfavorable and any new growth will not have the disease. Also fungicides will usually not control the disease curatively, rather, prevent it from affecting new growth if applied consistently. This is because most fingicides are preventive in their action. So if you consistently get this disease the best plan of attack is to apply it early in the season before you see disease and then apply regularly throughout the growing season.

I'm sure the neem helped some. I guess next time leave one untreated and see if there is a difference.

Daylily Leaf Streak

Pathogen: Aureobasidium microstichum, previous name: Collecephalus hemerocalli

Symptom: (see photo 1 below) Initial symptoms consist of leaf spots which often form along the mid-vein. These spots often have an orange coloration, leading people to suspect daylily rust. These are more angular and elongated than those formed by rust. When spots coalesce, extensive necrotic areas develop and the tissue surrounding this becomes chlorotic. Leaf dieback symptoms follow and usually develop from the leaf tip downward. Spores, which cause additional infections, are produced in the necrotic tissue. Heavily infected leaves often wither and die.

1. Symptom of Daylily Leaf Streak 2. Mycelium of Aureobasidium microstichum

Pathogen cycle: The fungus (see photo 2 above) persists through the winter within dead leaf tissue. In the spring or summer, with the return of favorable conditions, spores are again produced and provide the source for initial infections. Disease development is dependent on moisture supply and temperature. When temperatures are above 90F, disease development slows. Rainy periods and overhead irrigation increase infection and enhance symptom development, since spore dissemination occurs naturally by splashing water. Plant to plant spread can also occur when people or animals move through wet foliage.

Management: Wider spacing of plants to increase air circulation and management of overhead irrigation will aid in control by allowing leaves to dry. Remove and destroy dead leaves after the first hard freeze. Avoid purchasing plants with any symptoms of the disease.

Varieties vary markedly in their resistance. Resistant varieties include: Betty Bennet, Edna Spalding, Ella Pettigrew, Globe Trotter, Nancy Hicks, Pink Superior, Ron Rousseau, Sudie, Tropical Tones, Upper Room, and Winsome Lady. Races of the pathogen exist therefore, disease may still occur on these varieties.

It is important to start sprays at emergence of new growth. Make 3-4 applications at 2-wk intervals. If sprays are not initiated until first sign of disease, continue sprays at 2-wk intervals through bloom. The 2006 Georgia Pest Management Handbook lists Daconil 2787 and Daconil Ultrex. Daconil 2787 can be used by home gardeners. The 2006 North Carolina Agricultural Chemicals Handbook also lists mancozeb and thiophanate-methyl products. There are formulations of these products and/or active ingredients registered for use in South Carolina.

Puccinia hemerocallidis

Daylily Rust was first found in Georgia and Florida in 2000 and has since spread to 30 other states, including Massachusetts . The pathogen is native to Asia and is thought to have entered the United States on infected plant material from Central America . P. hemerocallidis first appears on the leaves as small, water soaked spots which expand and become raised to form pustules on both upper and lower leaf surfaces. Yellow-orange to orange-red spores are released from these pustules and can be carried by wind, water, workers, and tools. Although different cultivars react differently, most often infected leaves yellow, turn necrotic, and dry up. It is not known whether infection of tubers occurs. P. hemerocallidis requires two distinct hosts to complete its life cycle (heteroecious rust). The alternate host is the perennial Patrinia six species of this genus are grown and sold as ornamentals. However, on Daylily P. hemerocallidis produces polycyclic or repeating stage spores (urediospores) and does not require the alternate host for disease development. Once a Daylily plant produces spores the disease can spread rapidly to other Daylily plants. Following inoculation of leaves, infections can appear in as little as two to three days. Not only does the rust have a short incubation period, but it also spreads fairly quickly in nurseries.

Daylily varieties differ in susceptibility to the rust. In Massachusetts daylily rust was diagnosed on the "Twice as Nice" daylily collection. The cultivars 'Raspberry Candy' and 'All Fired Up' are the two cultivars in this line that have shown the worst symptoms, with other cultivars, such as 'Moonlight Masquerade', showing less severe symptoms. There are fourteen cultivars in this product line. Varieties in other states which have been reported to be affected since 2000 include: Attribution, Gertrude Condon, Crystal Tide, Colonel Scarborough, Starstruck, Joan Senior, Imperial Guard, Double Buttercup and Stella De Oro. Symptoms range from bright yellow spots to streaks.

Suspect Daylilies should be confirmed by a Diagnostic Lab. Contact M. Bess Dicklow at the UMass Extension Plant Diagnostic Lab at (413)545-3209, [email protected] . Sanitation is very important in managing this disease. Remove and destroy all infected plants. Purchase disease-free plants from reputable growers and propagate only from clean plant material. Minimize periods of leaf wetness by avoiding overhead watering and proper plant spacing. Protect uninfected plants with azoxystrobin (Heritage), propiconazole (Banner Maxx), myclobutanil (Eagle), chlorothalonil (Daconil), thiophanate-methyl (Cleary's 3336), triadimefon (Strike), or triflumizole (Terraguard). Check labels for broad crop clearance before applying fungicides.

More information and photos of daylily rust are available from the following websites:

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