Hybrid lily production is well suited for specialty cut flower growers selling to retail florists or at farmers’ markets. High quality fresh cut lilies have a distinctive competitive edge over lilies grown outside of its region. Local growers are able to harvest lily stems with one flower open and store them in water to deliver a fresher product. Boxed lilies, however, are harvested with only one large well-colored flower bud to avoid damage during shipping. Also, ethylene build-up in shipping boxes decreases the shelf life of most lilies grown out-of-state by 5 to 7 days.
The commercial production of bulbs sold to cut flower growers requires a cool environment, which is not found under East Coast climatic conditions. For this reason, most bulbs used for cut-flower production are grown in the Netherlands, Chile, New Zealand, South Africa, France and the Pacific Northwest in Oregon and Washington State.
The six main groups of lilies are Asiatic, Oriental, OT, LO, LA, and TA hybrids. Although Asiatic and Oriental lilies are well known to the general public, there have been many new releases of LO, LA, TA, and OT hybrid lilies brought onto the market. These new hybrids provide an opportunity to introduce the public to new possibilities in stem length, flower shape, size, color, and scent. Growers can expect to see many more new and exciting cultivars in coming years.
Hybrid lilies are a result of genetic crossings between lily species, making newer lily cultivars difficult to classify into conventional groupings. The OT hybrids are a cross between Oriental and Trumpet lilies. Oriental and OT lilies have fragrant flowers with some cultivars having stronger scented flowers than others.
For customers sensitive to strong odors, LA hybrids may be a better choice. The LA hybrids are a cross between L. longiflorum and Asiatic lily. The LA hybrids are increasing in popularity compared to the Asiatic hybrids. LA hybrids generally have a larger flower size and the flowers are more clustered at the top of the stem and are more upward facing than Oriental lilies. The LO hybrids are a cross between L. longiflorum and Oriental lily. LO hybrids will provide unique flower shapes, sizes and colors. The latest two additions are TA hybrids, which are a cross between the Trumpets and Asiatics, these hybrids will provide a deeper pigment color and will ultimately start replacing a lot of the LA varieties in the markets. The LA-hybrids have pretty much replaced the Asiatics in the cut flower market place. Last, but not the least we have the double flowering Orientals such as the RoseLily® series. Double Orientals do not have any pollen, rather they have an extra layer of flower petals that makes them unique and they have a more pleasant fragrance.
|LILY GROUP||BULB SIZE (cm)||# OF BULBS PER CRATE|
Note: For smaller quantities, some suppliers pack bulbs in bags of twenty-five. Also, the shape of the bulb influences how many bulbs are packed in a plastic crate. For example, LO hybrid lilies have a shape that differs from the OT hybrids, making packing tighter for OT compared to LO hybrids. Please confirm with your supplier the unit count.
at 50 - 55 °F
facing (U) or
|Deep D. Red||Landini||3-6||90||85||U|
|Forcing Time in
at 50 - 55 °F
or Side-facing (S)
in Greenhouse (days)
at 58 - 62 °F Night
or Side-facing (S)
|Forcing Time in
(days) at 58 - 62 °F
or Side-facing (S)
Bulb size (18/20 cm)
in Greenhouse (days)
at 58 - 62 °F Night
|Flowers Upward-facing (U)
or Side-facing (S)
(bulb 16-18 cm)
|LILY GROUP||NIGHT TEMPERATURE||DAY TEMPERATURE|
|LAs and Asiatics||50-55 °F||62-65 °F|
|Os, OTs, LOs||58-62 °F||65-68 °F|
Recommended Bulb Sizes
Bulbs are measured by circumference (cm) in a horizontal plane at the middle height of the bulb. Selecting smaller bulbs produces weaker stems and fewer flowers. Very small bulbs often result in no flowers being produced. Size does matter!
Bulb Storage and Handling
Lily bulbs ready for production are available year round from bulb suppliers. Suppliers pre- cool the bulbs for 6 to 8 weeks at 34 to 36 °F to ensure that they flower more evenly. Once the bulbs are precooled, suppliers freeze them in peat moss at 28 to 29 °F for storage. Freezing the bulbs prevents sprouting, reduces loss of bulb energy reserves, and minimizes disease occurrence.
Growers should open the shipping unit immediately upon arrival. Uncover the bulbs to let them air out and allow them to thaw before planting if they are still frozen. Bulbs can be stored in a cool room overnight at temperatures no higher than 60 °F. If planting must be delayed, bulbs can be held for up to two weeks in a cooler at 34 to 36 °F. Do not refreeze the bulbs or the flower buds may not develop properly.
After bulbs have been thawed, they should not be exposed to temperatures above 36 °F for periods longer than 8 to 12 hours or premature sprouting will occur. If the shoots of unplanted lilies have grown beyond 2 inches, the bulbs are worthless. Oftentimes lily bulbs available through local garden centers or large chain stores are held in heated retail areas, reducing the quality of the lily bulb. Although these bulbs are adequate for a homeowner’s gardening purpose, professional growers are not advised to use them for cut flower forcing.
There are several production methods available when growing lilies as a cut flower crop. Lilies can be grown in raised beds in the field, in high tunnels, and in greenhouses. Lilies can also be grown in crates in greenhouses. Before choosing a production method, or a combination of methods, growers should consider factors such as facilities and resources available, the types of lilies to be grown, and the time of year for growing the lily crop.
Fall and early spring production of lilies requires the use of high tunnels. High tunnels extend the season by allowing growers to start 6 weeks earlier in mid-February and by allowing them to plant Asiatics and LA hybrids up until early August to obtain a fall harvest. Growers can plant precooled LA bulbs in the field from March through June. For early spring and late fall production of Oriental and LO hybrids, it is recommended to grow them in a heated greenhouse to maintain minimum optimal night temperatures (Table 7). Heated greenhouses allow for year-round production. Winter production in the greenhouse takes around 5 weeks longer than in the spring and also requires the use of supplemental lighting. Maintaining proper air circulation using horizontal air flow (HAF) fans and top vents is very important for reducing disease problems in greenhouse production systems.
Field Site Selection and Management
Select a site that receives a minimum of 6 to 8 hours of sun daily to allow the flowers and foliage to dry off by evening, which decreases the chance of Botrytis. Choose a loam soil with 2 to 5 percent organic materials that is at least 6 to 8 inches deep. The soil should be well drained and have a pH of 6.3–6.8. Apply a pre-emergent herbicide soon after planting. The following chemicals are labeled for use around lilies: isoxaben (Gallery) and S-metolachlor (Pennant Magnum). Use Round-up in late winter as a post-emergent weed control.
Raised beds are useful for lily production because they help to improve drainage and prevent disease problems caused by root rots. An indoor raised bed can be constructed using pressure treated wood to create a 6-inch high side. There are also alternatives to pressure treated wood products like plastic wood, or decay resistant woods like black locust and osage orange. Leaching of copper from pressure treated wood should not be a problem if soils are high in clay or organic material. Wrapping pressure treated wood in plastic would prevent copper from leaching into soils. When constructing the raised beds in a high tunnel or greenhouse, consider the space between the beds for maneuvering equipment. During the heat of the summer when a greenhouse is not in use, plastic covers can be used to solarize the soil for 4 to 6 weeks. Solarizing the soil helps to reduce weed and disease problems the following season.
Greenhouse Crate Production
Lily bulb shipping crates can be reused for production in the greenhouse. Place newspaper on the bottom of the crates to prevent losing substrate. Use a well-drained commercially available soilless substrate. Your own mixture of well composted yard waste, peat, and wood fiber in a 1:1:1 ratio could also be used. A commercial blend is highly recommended. We have grown it in leaf compost with a well mixed in aggregate in crates and in the ground. It has performed well. Lilies respond well to organic matter, but the substrate has to be well drained.
Place a 2-inch layer of substrate at the bottom of the crate, lay the bulbs out, fill the rest of the crate with substrate, and water well. Keep the crate in a cool area between 50 and 55 °F for 7 to 20 days before placing it in the greenhouse to keep the bulbs from developing shoots before establishing an adequate root system. It is important to take the trays out of the cool area and into the light, whenever sprouts have developed 2 to 3 inches in height.
|LILY GROUP||LOW LIGHTING||HIGH LIGHTING|
|Os, OTs, LOs||10 to 12||12 to 15|
|Asiatics and LAs||12 to 15||15 to 20|
Note: Spacing is dependent on individual varieties. Tulip crates are too shallow for lilies to develop an adequate root system. Additional shipping crates can be purchased separately from your bulb supplier.
In raised beds, place drip tape with emitters at 8-inch intervals. For crate production, you can use two trickle tapes over each row of crates. However, growers should take into consideration how often the crates will need to be moved before deciding to install an irrigation system. Lack of frequent watering produces smaller flowers and shorter stems, so do not allow soil to dry out. Irrigate plants after cutting to maintain bulb vigor in field production situations.
Proper fertilization for lilies used as cut flowers is important. With a pH/soluble salt meter, monitor the pH and electrical conductivity (EC) of the soil using the 1:2 dilution method. The soil pH should be in the 6.3 to 6.8 range for optimum nutrient uptake and plant growth. This pH range is good for growing lilies both in the ground and in soilless substrate in the greenhouse. For greenhouse production of lilies, soil samples should be taken every week during the growing season and the soluble salt and pH monitored using a portable pH and EC meter. Acceptable EC readings for production in containers should be between 1.0 and 1.5 ms/cm. High soluble salt levels can cause soft stems, leaf burn, and reduced plant height because of inadequate root development. In greenhouse and high tunnel production systems fertilization should begin at shoot emergence, using a fertilizer with a 2:1 ratio of calcium nitrate to potassium nitrate. Weekly application of this ratio can be used or 250 to 300 ppm of N should be applied. The use of slow or controlled release fertilizers is not recommended, as the stems will be harvested before most of the nutrients are released.
In field production systems, a soil test will determine any necessary nutrient and amendments additions. Fertilization should begin at shoot emergence. If applying a granular fertilizer, use one that has 30 to 50 percent water insoluble nitrogen (WIN) so it will be supplied throughout the growing season. Apply 1 to 1.5 pounds of nitrogen per 1,000 square feet. If the lilies are left in ground for a second season, test and adjust the pH as necessary during the fall/winter period. Phosphorus should not be applied if the fertility index value for phosphorus (P-FIV) is above 150. If phosphorus levels are low and the phosphorus level needs to be increased, avoid the use of super- phosphate as it may lead to leaf-scorch damage from fluoride. Commercially available substrates, well-water, and pond water are generally fluoride free, but municipal water may contain fluoride. Water should be tested for fluoride and other dissolved minerals including carbonates and bicarbonates which need to be neutralized with acid, especially when growing in soilless substrates.
When growing lilies in soilless substrate, the bulbs should be discarded after harvest. Do not re-use the substrate because of the increased chance for root rot diseases. When lilies are grown in the field, the bulbs will produce marketable flowers for 2 to 3 years before flower production drops in yield and flower size. Do not rotate flower bulb crops into a lily field for 5 years.
OF CALCIUM CHLORIDE
OF CALCIUM (PPM)
Lilies are given supplemental light from late September until early April to extend the day length to 16 hours. The number of hours of lighting necessary to manipulate the day length to 16 hours will vary depending upon the exact time of year. Increased light levels will also help to avoid bud abortion and keep the plants from leaning south. Start lighting plants when the foliage emerges. Initially you can use 2,500 watts of halogen lighting or one high intensity discharge (HID) light per 100 ft2 placed 6 to 8 ft above the crop. The use of HID lights is preferable to incandescent or fluorescent lamps because of high efficiency, uniform light distribution, and a lower amount of shading. Based on 2006 figures, a 30 x 48 ft greenhouse used three 1,000 watt fixtures, which cost $350 each and an automatic timer that cost $60.
Cut stems may be sold when flowers are open for local markets, but harvesting in the bud stage to allow the flowers to open after the customer has taken them home is preferred. Harvest lilies when the first, lower-most bud shows full color but has not yet opened. If lilies are harvested at an earlier stage, buds may take longer to open, may not open completely, or may be misshapen. Remove the anthers on open blooms to prevent pollen from soiling the flower or any surfaces on which it might fall. The best time to cut lilies is when temperatures are below 80 °F or early in the morning. Handling the flowers in temperatures above 80°F will bruise the flowers. Harvest and place stems into water using clean plastic buckets. Do not use any galvanized buckets for harvesting cut flowers because the coating on the bucket creates an oily residue in the water that clogs the stems.
Post Harvest Handling
Place cut lily stems in water in a cooler at 35 to 41°F an hour after harvesting to avoid shocking the flowers. Handle lily blooms carefully at all times because the flowers bruise easily. Remove the bottom one-third of the foliage and grade the stems by size. Depending upon the market, grading can be done by the stem length or by the number of flowers per stem. Lilies may be bunched into desired quantities and sleeved, again, depending upon the market.
Cut lily stems should be transported in water to prolong the vase life. Freshly harvested lilies have a vase life of 9 to 14 days, depending upon the cultivar and the environment. The vase life of freshly harvested lilies can be extended by the final customer if they are re-cut and placed in a solution containing a floral preservative. Floral preservatives can also be added to the water used for storage prior to shipping, upon receipt at the retail level, and in floral arrangements. Hybrid lilies are sensitive to ethylene; keep them away from ripening fruit, maturing foliage and flowers, or any other ethylene source. Anti-ethylene treatments are effective on many lily cultivars, especially on Asiatic lilies.
Calcium deficiency is occasionally a problem in greenhouse production. Some Oriental lilies are susceptible to a condition known as “upper leaf necrosis” (ULN), which causes distortion and necrosis of the upper leaves. Problems with ULN have been reported primarily on Oriental type lilies, which have a low calcium content in the shoot and bud scales of the bulb.
The bulbs have enough calcium to supply the lower leaves of the plant, but the rest must come from the soil. Growers can improve nutrient uptake by monitoring for root rots and soluble salts. Calcium deficiencies can develop even when there is an adequate amount of calcium in the soil. In those instances, adding calcium to the soil would not be beneficial because the deficiency is a result of uneven distribution within the plant.
Calcium is taken up by the roots and trans- located only to transpiring tissues. Calcium will not move into the young leaves of the plant if they are not actively transpiring. A low transpiration rate due to high humidity or low light intensity increases the likelihood of lilies developing ULN.
Transpiration rates can be raised by increasing light intensity and decreasing humidity. Avoid growing plants under shady conditions and provide supplemental lighting during the winter months. If possible, keep air circulating with horizontal air flow fans. Keep the leaves and the greenhouse as dry as possible. Overlapping leaves can also restrict transpiration. On Oriental lilies, the leaves associated with the flowers are overlapped by older leaves before the buds develop. These are the same upper leaves that display symptoms of ULN.
Symptoms of upper leaf necrosis appear long after the actual damage has occurred, so most growers catch the problem after it is too late.
Some preventative measures include using a calcium nitrate fertilizer and applying foliar sprays of calcium chloride. Use caution; foliar sprays can be phytotoxic if applied improperly. Ample air flow will help tremendously with reducing ULN. Let your lilies move by running enough airflow through greenhouse.
Bud abortion is the first sign of lilies growing in a stressful environment. Lilies will forego flower buds as a survival technique. Stress occurs from excessive heat and/or inconsistent watering practices. Lilies need consistent and thorough hydration, especially in the summer time. Light levels below 460 foot-candles (60umol·m-2·s-1) can also cause bud abortion in the winter.
Aphids can rapidly become a major pest on lilies if left unchecked. Because aphids feed on the plant fluids within the phloem of leaves and green stems, heavy populations may measurably reduce plant vigor. Aphids spread many plant viruses. They excrete large quantities of sugar-rich honey dew on which sooty mold fungus may grow. Before any attempt is made to control aphids, the species should be identified. After the species is identified, familiarize yourself with its biology on a particular lily crop. Note whether it prefers particular species or cultivars of lilies, if it feeds selectively on certain parts of the plant, and how rapidly it reproduces.
The aphid that is specific to lily is called the lily aphid, Neomyzus circumflexus. The lily aphid, Neomyzus circumflexus (Buckton), is a crescent-marked lily aphid, and is one of the common aphids to attack lily plants in the field and greenhouse. Reported food hosts in addition to lily include Adianthum, Cineraria, Cyclamen, Fuchsia, and Zantedeschia.
The immature or nymphal form of lily aphid is pale greenish white and does not have the dark crescent bands found on the adult. Adult aphids may be either apterous (without wings), or alate (with wings). The apterous female is whitish to pale bright green, shiny and 1/18 to 1/12 inch long. The tip of the abdomen usually has a dark brown to black horseshoe-shaped patch. The antennae are pale with black joints and about 1/10 the length of the body. Legs are pale brownish yellow and slightly darker at the tips. Eyes are dark red.
Insecticidal soaps offer some control against aphids. Applications should be applied at regular intervals for maximum efficacy. Growers with aphid problems can apply foliar or soil drenches of a labeled neonicotinoid. Check the Total Crop Management for Greenhouse Production (2016) manual for a recommended systemic pesticide. Newer systemic insecticides such as Altus and Mainspring are effective with minimal impact on beneficial organisms and parasitoids. Stylet blockers such as Endeavor and Aria are very effective with minimal impact on beneficial organisms.
If you grow lilies in greenhouses, check plants before moving them indoors to make sure they are free of aphids. Control weeds under greenhouse benches and outdoors in areas adjacent to the greenhouse to prevent aphid populations from developing. Aphids can be prevented from migrating into the greenhouse by covering vents and doors with a 300 holes-per-inch mesh screening.
Grasshoppers often are the most common insect invaders of cut flower production fields and among the most difficult pests to control. For a variety of reasons, grasshopper populations cycle naturally from season to season, causing extensive damage during outbreak years. Annually, grasshopper problems tend to increase as summer progresses and usually continue even after the first frost. Grasshopper populations often build up in weedy and tall grass areas near cut flower fields.
It may be useful to leave an uncut barrier strip of grass to concentrate grasshopper populations. Treat these barrier strips with insecticide for greater control. The insecticides Acephate (Orthene) and a synthetic pyrethroid can be applied to control grasshoppers. Guinea hens, heritage breed turkeys, and chickens may be used to supplement grasshopper control in some cut flower operations. Guinea hens are very efficient in reducing grasshopper populations. They are known as a “watch dog” bird and can be rather noisy. Consider this characteristic if your operation is located in a residential area.
Nosema locustae, a disease-causing protozoan, is available to control grasshoppers. The protozoan is on a grain carrier. The material is applied to tall grassy and weedy areas where grasshopper populations are building up. The material needs to be applied in early to mid summer to keep grasshopper populations low. N. locustae applications may cause some reduction in grasshopper numbers in a few days or weeks, but in general it is a slow- acting and debilitating disease of grasshoppers that takes at least a whole season to affect grasshopper populations. This protozoan is not effective against all grasshopper species and is much more effective against young grasshoppers. Combinations of insecticides for rapid knockdown and Nosema for long-term control may be useful.
Lily Leaf Beetle
The lily leaf beetle is one of the greatest threats to lily producers. This insect is an invasive species that is native to Europe and northern Africa and was first reported near Montreal, Canada, in 1945. It is suspected that it came from Europe on a delivery of lily bulbs. In 1992, the beetle was found in Cambridge, Massachusetts. By 2005, growers in New Hampshire, Maine, Ontario, and Massachusetts reported that it was devastating their lily plants. Fortunately, it has not been found yet in Maryland as of January 2021. Lily growers must remain alert to detect this pest if it is accidentally shipped into Maryland. If you find a beetle in a shipment of lilies, contact the Maryland Department of Agriculture or your local Extension office.
The lily leaf beetle is in the family Chrysomelidae (leaf beetles). Its Latin name is Lilioceris lilii, which tells you it loves to feed on lily plants. It does not confine its feeding just to lily. It has been found feeding on solomon’s seal, bittersweet, hollyhock, hosta, and even the common potato. It does not attack daylilies.
Lily Leaf Beetle Identification
The adult beetle has a shiny, scarlet-colored body and black legs, head and antennae. If you flip over the beetle, you will see that its underside is black. The beetle is small compared to other beetles, varying from 1/4 to 3/8 in length. If squeezed lightly, this beetle will give off a slight squeak by using the wing cover and an abdominal stridulating body part.
The larvae of this beetle are slug-like with a swollen body and black head capsules. Their bodies can be orange, yellowish, or green colored. Lily leaf beetle larvae tend to place their excrement on their backs. The early instar larvae feed on the underside of the foliage and can go undetected unless you are examining the underside of the foliage regularly during the summer. The later instar larvae feed on the underside and top of the foliage. They also feed on the flower buds and stems of the plant. After feeding in the last instar, larvae migrate to the soil to pupate.
The pupal stage is a shocking florescent orange. You can easily pick up this brightly colored beetle pupa if you probe through the soil. The pupal stage lasts a little over 2 weeks, and then the adults emerge to start a new generation. Adult beetles overwinter in leaf litter. The adults emerge in early April in most northern states to start a new generation. Female lily leaf beetles are prolific egg layers. A healthy female lays up to 450 eggs in irregular lines on the underside of the foliage. The beetles are active throughout the summer into the fall with up to 3 generations in northern states.
Lily Leaf Beetle Control
There are several control options for the lily leaf beetle. For light infestations, remove larvae and beetles by hand. Look for the eggs on the undersides of the foliage and make sure you cut off leaves with eggs and get them out of the area. If this method is too time consuming, then consider applying a soil drench of imidacloprid, which will provide 8 to 12 weeks of control. If you want to try a botanical insecticide, then use a neem-based insecticide such as Azatin, Aza-Direct, or BioNeem. Neem works best on early instar (young) larvae. There are four parasitic wasps that are used for biological control in France and Switzerland. One species of European parasitoid has been released in the Boston area and in Cumberland, Rhode Island. The efficacy of this biological control is still being evaluated.
Two species of the fungal pathogen Botrytis commonly infect lilies: Botrytis elliptica, and B. cinerea. While B. cinerea has a wide host range including many herbaceous ornamentals, B. elliptica infects primarily lilies. The first symptoms are pale tan spots on leaves, stems, or petals. The spots may enlarge rapidly, producing general blight and collapse of tissues. Under humid conditions, a gray velvety or fuzzy mold containing large numbers of spores may be seen on the blighted plant parts.
Botrytis can enter a production area as small, dark structures called sclerotia that can persist in the soil. The fungus can also survive in infected plant debris in greenhouses. Spores develop from sclerotia or debris, and move in air currents. Infection requires a film of water on the plant surface, and can occur over a wide range of temperatures.
Sanitation and good cultural practices are essential in managing Botrytis outbreaks. Botrytis can grow quickly on debris such as dropped petals, so keep production, cutting and flower storage areas clean and free of plant debris. Reducing leaf wetness is also essential for Botrytis management. Keep foliage and leaves as dry as possible. Space plants to allow good air circulation. Venting the greenhouse in the evening, then heating the cooler air from outside helps prevent dew formation on plants during the night. Use horizontal air flow (HAF) fans to reduce humidity in the crop canopy. Avoid overhead watering: water the substrate, not the leaves.
Fungicides can help manage Botrytis blight but must be used along with good cultural practices. Alternating or tank-mixing products with different modes of action is important to prevent resistance development within Botrytis populations. Fungicides effective against Botrytis include azoxystrobin, chlorothalonil, iprodione, fenhexamid, fludioxonil, copper-based products, iprodione and mancozeb. Biocontrol products must be applied prior to infection, and include products containing Bacillus amyloliquefaciens (such as Triathlon or Companion) or Bacillus subtilis (Cease).
Root and Bulb Rots
Lilies can be attacked by several root rots caused by fungus-like water molds such as Pythium species, and true fungi such as Rhizoctonia and Fusarium. Aboveground symptoms of root and bulb rots include yellowing foliage, stunted plants and overall poor growth. Diseased roots will be discolored and pull apart easily. Dark brown or reddish lesions may develop on bulb scales and the bulb basal plate. Severely infected plants will be killed. Pythium root rot is favored by excessive irrigation and poor soil drainage. Rhizoctonia root rot usually is more common during warm/hot weather, and can cause a brown stem rot as well as root rot. Lab tests are required to determine which pathogen is causing root rot. Pythium often causes the root cortex to slough off, leaving the vascular cylinder exposed (a symptom called “rat-tailing”). Rhizoctonia may produce tan dry, sunken lesions on roots and bulbs. Root rot pathogens can be present in field soil or can be introduced to potting mixes on field-grown bulbs. Fungicides, applied as bulb dips or soil drenches, can be helpful in preventing these diseases, but choice of product depends on which pathogen is to be targeted. Always follow label instructions for specific products. Products effective in protecting plants from water molds such as Pythium root rot include mefenoxam (Subdue Maxx) and etridiazole (Terrazole). Products effective against Rhizoctonia and Fusarium include fludioxanil (Medallion), propiconazole (Banner Maxx), and strobilurin products like Heritage and Compass.
Blue mold, caused by Penicillium spp., can develop in bulbs during storage, especially if the bulbs were damaged during harvest. Look for brown bulb lesions that may be covered with blue to green powdery fungal growth as an indication of blue mold, and discard bulbs with these symptoms.
Southern blight, caused by the fungus Sclerotium rolfsii, is a disease in warmer climates. The pathogen produces white thread-like mycelium and small, tan sclerotia that resemble millet seeds, on the stem and surrounding soil. Infected plants will develop wilt symptoms, and die as the stems become girdled. The fungus remains in the soil as dormant sclerotia. Diseased plants can be dug up with surrounding soil and discarded. If the field has a history of this disease in small localized areas, fungicide ‘spot-treatment” drench with a product such as azoxystrobin (Heritage) may help reduce disease.
Symptoms of virus infection in lilies include foliar mosaic (bright to faint yellow mottling and streaking), leaf distortion, stunted plants and abnormal color development (streaks, spots or color breaks) in flowers. Viruses can be spread through propagation from infected plants, and by insects such as aphids. Many bulb producers periodically test their propagation stock for virus infection, and only healthy stock is used. However, if lily bulbs are carried over year to year, the chance of virus infection increases.
The most common viruses infecting lilies are Lily symptomless virus (LSV) and Lily mottle virus (LMoV), which have spread world-wide through movement of infected bulbs. Cucumber mosaic virus (CMV) is commonly seen in a number of crops and weeds in the mid-Atlantic region and can be vectored by aphids in lily plantings. Plantago asiatica mosaic virus (PlAMV) has recently been detected in lilies in Europe and the US.
Management of virus diseases involves planting virus-free bulbs from reputable producers, and roguing out any plants with virus symptoms as soon as possible. Infected plants cannot be cured. Weed control can help reduce infection from certain viruses, such as CMV, which have weed hosts. Management of insects such as aphids will help reduce spread of the viruses they vector. Other problems, such as herbicide damage, can produce symptoms similar to those of viruses. Specialized laboratory testing is required to confirm virus infections.
Plant parasitic nematodes are microscopic worms that feed on plant tissues and can occasionally affect lilies. Root knot nematodes (Meloidogyne spp.) can damage lilies grown in field soil production. Female nematodes feed within plant roots and induce swellings (knots) which give the roots a bumpy appearance. Root knot nematodes have a wide host range, including weed hosts, allowing populations to persist in fields.
Lilies can also be infected by two nematodes that feed on bulbs, stems and leaves. Stem and bulb nematodes (Ditylenchus spp) cause lesions on bulb scales as well as distorted leaves and stunted plants. Foliar nematodes (Aphelenchoides spp.) cause discolored streaks in foliage. Both nematodes can be introduced to a crop on contaminated bulbs or plant material.
Use of soilless mixes will help avoid root knot nematode problems. Purchase bulbs from reputable companies, and inspect bulbs for symptoms of nematode issues. Rogue out and destroy plants infected with stem and bulb or foliar nematodes, and do not re-use potting mix from diseased plants. Steam treatment or fumigation of soil beds between crops can help manage root knot nematodes.
Chang, Y. and W. B. Miller. “Upper Leaf Necrosis on Oriental Lilies.” FloraCulture International, May 2004.
Chastagner, G., J.M. vanTuyl, M. Verbeek, W. B. Miller, and B. Westerdahl. “Diseases of Lily”, Pages 1231-1287 in Handbook of Florist Crop Diseases, R.J. McGovern and W.H. Elmer, eds. Springer, 2017.
De Hertogh, A. Holland Bulb Forcer’s Guide. Hillegom, The Netherlands: The International Flower-Bulb Center, 1996.
Dole, J. and H. Wilkins. Floriculture Principles and Species: 2nd Edition. New Jersey: Prentice Hall, 2005.
Gill, S.A., E. Dutky, and D. Clement. Pests and Disease of Herbaceous Perennials: 2nd Edition. Bativa: Ball Publishing, 2006. (In press.)
Gill, S.A., K. Rane, A. Ristvey, J. Latimer, C. Schuster, B. Whipker, and D. Smith-Fiola, Total Crop Management for Greenhouse Production. University of Maryland Extension Publication. 2016.
Runkle, E. and Heins, R. “Leaf Tip Burn on Oriental Lilies.” Michigan State University Greenhouse Alert, Issue 8, 2003.
Disclaimer: The use of brand names in this fact sheet does not express or imply an endorsement by the University of Maryland Extension.