Diseases And Problems Of Daylilies
Daylilies are highly valued for their gorgeous multi-hued flowers and foliage, which makes these plants perfect for use as ground covers. The flowers of this species are named “daylilies” as they only remain in bloom for a day. However, the flowers of any one plant are constantly replaced by new flowers on the next day and the flowering season continues for six weeks. Unlike many other flowering plants, daylilies are usually not bothered by diseases. Nevertheless, they do face specific challenges and, hence, need to be grown in soils having excellent drainage and loads of organic substances.
Bacterial soft rot
This condition is also referred to as crown rot and is a result of damages caused to the crown or roots perhaps by nematodes, enabling bacteria like Phytophthora, Pythium, Fusarium and Rhizoctonia, which may be present in several soils, to infiltrate the plant tissue. Once any of these bacteria penetrate the plant tissue, it leads to rapid infection of the crown, foliage and roots, resulting in the plant turning out to be a soggy mess having a foul smell. While it is difficult to treat the plants once they have been infected, but undertaking treatment using Streptomycin may be useful.
Usually, the bacterial soft rot assaults plants that have been planted newly or those that have been divided recently. Hence, it will be prudent if you undertake precautionary measures for such plants. It is advisable that you ensure that the wounds of the divided plants have dried completely before transplanting them. This will allow the formation of new epidermis. It has been found that the chances of the rot occurring is higher when the temperature and humidity are very high and the soil is too damp. Probably, bacterial soft rot is gene-related, as this condition passes onto new plants through somewhat narrow, but distinctive breeding lines.
In fact, bacterial soft rot is not a major problem for plants grown in colder as well as cooler climatic conditions, provided a plant has not already been infected by the bacteria while grown in its nursery located in a hot climate.
Granular fungal rot
Normally, this condition does not bother gardeners in Europe. It has been seen that granular fungal rot or Cercospora hemerocallis has a tendency to assault daylilies that are probably without any genetic resistance to fungi or those that are under stress. When a plant is attacked by Cercospora hemerocallis, initially its leaves develop yellowish streaks and all of a sudden, mature daylily clumps may develop a stratum of minute, spore sacs having a brownish-black color. This fungus generates a white, thread-like mesh that spreads rapidly over the affected plant’s leaves and crown. As soon as you notice any sign of this fungal disease, dig out the affected plant and get rid of all the affected parts. Subsequently, treat the remaining parts with a 10% bleach solution. Also ensure that you disinfect the soil in the region of the affected plants.
Leaf streak disease (Aureobasidium microstictum)
Basically, leaf streak disease is a fungal infection and is common virtually in all places wherever people grow daylilies. Often this condition is overlooked by gardeners, who usually attribute it to poor nutrition or leaf senescence. The infection occurs when the fungus Aureobasidium microstictum gets into the leaf through a damaged point. The first signs of this condition included development of somewhat darker green semi-transparent spots, which progressively turn necrotic and subsequently chlorotic. Eventually, these spots spread out in the form of streaks throughout the leaves. While not means have been developed yet to control the condition, it is advisable that gardeners need to emphasize on the hygiene of their gardens and focus on good cultivation. In fact, apart from helping to avoid leaf streak disease, these measures also help the daylilies to become further resistant to such attacks.
This condition is attributed to both forms of Botrytis or Colletotrichum, which results in changing the color of the leaves to yellow. If you find that your daylilies are affected by leaf spot, you should get rid of the affected leaves right away. At the same time, spray a fungicide that is effective for eliminating downy mildew (also known as false mildew).
Iris leaf spot (Mycosphaerella macrospora)
This is a fungal disease caused by Mycosphaerella macrospora, which lies dormant on leaf debris throughout the winter and transmits the disease to the foliage growth in the new season. The first symptoms of iris leaf spot include brown lesions having greyish centers. These lesions gradually increase in size till the leaf withers completely. If the condition is not checked, the robustness of the plant will start deteriorating soon. In order to combat this fungal infection, you need to get rid of the leaf debris at the onset of winter and administer a copper spray containing copper when the growth of the new season is about 20 cm to 30 cm (8 inches to 12 inches) high. It is advisable that you apply the fungicide once in every fortnight.
Thus far, no one is actually aware of what is responsible for the plant problems that are collectively known as “spring sickness”. The condition can appear in the form of a twisted or creased effect on the inner parts of the leaves. When the condition is mild, the daylily leaves may set straight and even have proper growth instead of turning brown and eventually die, while the scapes will come out in the summer in progress currently. On the other hand, if the daylily leaves are affected severely, no scapes will appear during the current summer and there will be no blooms either. This is mainly owing to the fact that when spring sickness in daylilies is severe, the tips of scapes are not able to force their way through soggy, rotting leaves. As a result, even the plant stops growing.
Usually, spring sickness affects plants growing in regions wherein there are many cycles of freeze and thaw conditions during spring. In fact, this effect may also be attributed to insect larvae that feed on the new growth inside the crown during spring. However, it is important to note that spring sickness is not connected with invasions by bacteria. When insect larvae feed on the spring growth, these new growths will have a pale green color with jagged, kinked or twisted margins.
Daylilies having a nocturnal ancestry appear to have better prospects of opening properly in the early morning, provided they are grown in places having colder to temperate climatic conditions with a moderate summer climate. Daylilies usually exhibit their best performance when they are grown in climates where the temperature during the day and night remains even. However, it does not necessarily mean that the temperatures during the day and night should be high, despite the fact that daylilies generally thrive best in places where the temperatures during the night do not drop below 18°C (65°F). According to some daylily growers, the temperature of a place during the preceding three or four days as well as nights can influence the ability of a daylily bloom to open properly early in the morning.
Since daylilies are becoming all the time more popular now, it is expected that more and more breeders will accept the challenge of developing more cultivars possessing the early-morning-opening gene. The main decisive factor for a daylily flower to open early in the morning is that they should be completely open before 6 a.m., true solar time.
The term “petal boating” is applicable for petals that have a creased or canoe-shaped look. This condition takes place following cool nights, particularly in daylily cultivars that do not possess early-morning opening genes. Usually, petal boating occurs in tetraploids having heavy substance with gold-wire or picotee edges, very frequently in daylily flowers having a prominent tongue-like petal that emerges higher than the other petals in the same arrangement.
This condition entails sepal reverses, which remain green even after the flower has opened. This is primarily owing to the fact that the pigments are yet to mature completely. Green sepals especially occur at the tip of the sepals and are owing to the flowering season that coincides with a string of cold nights. Green sepal reverse often occur in the daylily known as Hemerocallis “Eenie Weenie”. This condition is more obvious on flowers with paler hues.
This is a condition wherein the scapes of daylilies seem to have broken off horizontally of their own accord or, literally speaking, seem to have exploded. However, the split or blasting does not necessarily mean that the heads of the scapes have completely been separated. On the other hand, these “blasted” scapes may still produce flowers, subject to the fact that they are still connected by the cambium layer. It is believed that scape blasting occurs owing to availability of irregular amounts of moisture or due to excessive watering. This condition may also occur owing to presence of too much nitrogen in the soil. Scape blasting is more common in tetraploids. However, now breeders are endeavouring to remove this negative characteristic from tetraploid daylilies.
While scape blasting is a horizontal phenomenon, in scape cracking, the daylily scapes crack vertically. It may also be described as breaking of the scapes. Scape cracking is generally attributed to excessive use of fertilizers having an unbalanced composition. In case you intend to use the flower for the present year’s breeding, you can possibly help the scape to remain and produce blooms by supporting it with a stick. Scape cracking was a serious problem for gardeners during the time when early tetraploids were developed. However, today it is not seen as a severe issue.
It is a condition wherein there is a superfluity of shoots that are akin to grass and grow very closely in clumps of latent daylilies raised in places having cold climatic conditions and are endeavouring to acclimatize to hot weather conditions. The Siloams is an excellent example of grassing. This condition can be done away with by pulling out the shoots and replanting them separately. It is important to keep in mind that grassing is different from a soft crown, which possesses the potential to rejuvenate by developing small fans around the crown that has rotted.
Yellowing leaf tips
The leaf tips of daylilies may start turning yellowish when the plant has an opening or split at its base owing the enlargement of its crown caused by frost damage and the plant is beginning to get rid of its damaged leaves. If you find that the yellowish-brown tint on the leaf tips begins to gradually spread downward to the leaf base and a number of leaves are split, it may be attributed to spider mites.
Yellowing of basal leaves
When the leaves at the base of the plant start turning yellowish or brown, it is possible that it is owing to the normal response of the plant to unfavourable temperatures. It is important that you do not remove these discoloured leaves, as they may serve as a natural defence for the plant.