Common Lily Pests
Insects, Mites, and Other Pests
Normally, lilies are very easy to grow and take very little care. However, there are on occasion, some instances and conditions that need investigation to figure out what, if anything, is happening and I hope this article helps you.
In certain circumstances, lilies are prone to attack by several animal, insects, mites, nematodes, and other pests of all different sizes…from deer, elk, rodents to microscopic mites. The presence or absence of a pest depends on the region, climate zone in which the plants are grown, alternative or IPM (Integrated Pest Management) methods used, and what sort of treatments have been used (foliar or above ground, soil treatments, and systemic chemicals), specifically non-selective treatments or chemicals. However, you must understand that not all alternatives and chemicals are a 100% solution for every pest or problem, but should be used together. The best plan of attack is to use an Integrated Pest Management program, whether dealing with lily pests or any other plant pest for that matter. Alternatives to chemicals may work for several situations or pest, however, they are intended for a specific problem and can do more damage to your lily or plant if not used correctly. Be careful when using non-selective chemical or alternatives to chemicals, you can also kill your natural predators! One can be assured that insect, mites, and other pests are never as devastating as diseases such as Botrytis, Fusarium, or viruses, which can destroy whole crops and garden plantings in a very short period of time.
The most important insect or “bug” pests are aphids. These need to be controlled at all costs and as soon as they are noticed! Few insects breed more rapidly and spread viruses fast, so every measure should be taken to eradicate them on their first appearance, eggs included. This is crucial if one is growing varieties or species known to be susceptible to virus. All species of aphids that colonize lilies not only spread virus disease, but they also debilitate the plants physically, causing twisted leaves and flower buds along with stem distortion.
Aphids produce their young aggressively in large numbers. Remember, this is nature and all things in nature live by three rules…1.) Reproduce, 2.) Eat, 3.) Survive. On an infested plant one can often see large female aphids surrounded by scores of tiny offspring. These insects move by crawling and at times also produce winged migrant offspring that can fly for surprisingly long distances to colonize other plantings.
Granular systemic insecticides are the best way to control aphids and will not harm beneficial microbial or insect predators in the soil. When watered into the soil, the insecticide is taken up by the roots and absorbed through the conducting tissues of the plants. The aphids, being sucking insects, are then killed by the poisoned sap. This class of control is particularly effective in container plantings where the chemical remains concentrated longer. Systemic insecticide sprays, should be applied at the first sign of an aphid attack and thereafter on a regular basis until the pest is eradicated. They can normally be combined with a fungicide, but check the label first.Always read and follow label directions carefully. The systemic insecticide Orthene (e.g., acephate) has been used quite successfully for aphid control when mixed with water at a 1% solution. Contrary to some internet articles and other beliefs, its’ systemic action lasts for about ten days and can only be achieved by applying the mixture directly to the leaves. Malathion is a contact insecticide not a systemic. It will also destroy mites and any eggs that on the plant.
Mineral oil sprays can help reduce virus spread in many crops, including lilies. The film of oil kills the aphids and their eggs by smothering them a nd provides the lily leaf surface with a thin, protective barrier against near future invasions thus preventing Aphids from transmitting the disease through their style by clogging them. Oil sprays are considered to be somewhat effective in controlling viruses in commercial plantings. The weekly sprays used by most commercial growers may not be practical for home gardeners, but those with large lily plantings may find the effort worthwhile.
Be aware that oil spraying should be avoided during the heat of the day, when it may produce leaf scorch and distortion; try to do it just after sunrise or before sundown. A light summer oil, used at about 1 to 2 percent dilution, is effective. Oils are quite safe to use and can be combined with most insecticides and fungicides. There are various other systemic and contact insecticides that I will address in a future article, but these are the most common. A variety of products are available for fumigating greenhouses and I do not recommend this method for the home gardener. Too dangerous! Aphids, as well as a variety of other pests, are particularly troublesome in greenhouses, where the environment is perfect for their increase and their natural predators tend to be non-existent.
Insecticides available on the market change continually, but all must be used with the utmost care and caution. Always use rubber gloves and protective clothing; many insecticides can be absorbed through the skin and cause neurological damage.
Any spray can be dangerous to use on tender young seedlings. For this reason, it is better to control aphids, which are very attracted to seedlings, with a granular systemic insecticide, which is sprinkled on the soil and watered in. If aphids are continually moving into the planting from an outside source, efforts to control them are unlikely to be effective, unless the outside source can be treated, too. In extreme cases, hybridizers and other enthusiasts may grow lilies in aphid-proof screen houses; however, aphids can be carried into such structures on clothing or tools, so a spray program should be maintained or use insect predators, such as Preying Mantis. Migrant aphids can be inhibited from moving between plants by barriers of other vegetation or gauze; the barrier must exceed the height of the lilies.
Finally, aphids overwinter by laying eggs, which are produced in the migrant phase. It is thus important to destroy any dead plant material that may harbor overwintering eggs.
Bulb and Foliage Spider Mites
Spider mites are not a spider. They are members of the Acari (mite) family Tetranychidae, which includes about 1,600 species. They generally live on the under sides of leaves of plants where they may spin protective silk webs, and they can cause damage by puncturing the plant cells then sucking the chlorophyll from each puncture wound. Spider mites are known to feed on several hundred species of plant.
The loose structure of lily bulbs makes them susceptible to infestation by pests that live between the scales. Bulb mites (Rhizognyphus echinopus) are troublesome but usually secondary pests; they attack many other bulbs along with lilies.
The adult bulb mites are about the size of a pinhead, rounded, and yellowish white in color, often tinged with pink. The foliage mites are brown, red, light brown with two lightly colored brown spots. In warm climates they are usually present in large numbers, particularly just above the basal plate and between the scales, and on the foliage. They are so small, you’ll need a magnifying glass or hand held lens to see them. They attack the roots and basal plate and eventually enter the center of the bulb. On the foliage, mites will make many piercing holes in the leaf and suck the chlorophyll thus leaving rust colored speckles where they have pierced. The following methods of control may be used against mites:
- Treat bulbs with hot water at 44Â°C (111Â°F) for one hour.
- Fumigate dry bulbs with Para dichlorobenzene (the active substance in mothballs) in an airtight container. Spread the fumigant over the bottom of the container, using 4 grams per liter of air space and exposing the bulbs for 12 hours.
- Dust the bulbs, and all foliage parts with flowers of sulfur. This is probably the best method for the home gardener.
- Apply mineral oil sprays to the foliage as often as needed.
- Soak the bulb for five minutes in mineral oil.
- Destroy badly infested bulbs by burning them.
Deer, hares, rabbits
These herbivores often nibble on young growth, buds, flowers, seedpods, and other plant parts; however, they are seldom seriously destructive. In rural areas gardens can be protected by deer- and rabbit-proof fences, adequately maintained. The presence of a dog often deters deer from invading, and many cats will prey on rabbits and rodents.
Chemical controls and repellants, trapping, and shooting offer only temporary solutions, if indeed they are effective at all. Foul-smelling concoctions, both homemade and commercial, are sometimes effective against deer. The material is placed in muslin sacks and suspended around the plantings.
Leatherjackets, wireworms, and millipedes
- Leather jackets are the larvae of the crane fly or daddy-long-legs (Tipulidae). They are sluggish, legless, dull-colored brownish creatures that may reach 3.75 centimeters (1.5 inches) in length.
- Wire worms are the larvae of click beetles. They are slender, smooth, tough, and wiry creatures, measuring up to 2.5 centimeters (1 inch) in length. They are golden yellow and have six very short legs. These pests burrow into bulbs.
- Millipedes are dull-colored, sluggish creatures with many legs. They curl up when disturbed.
All these underground pests can be controlled by dusting the ground with benzene hexachloride (BHC) or Bromophos. A nonchemical control involves baiting with slices of potato, carrot, or other root vegetable placed below the surface of the soil. These traps can be skewered on a stick to mark their position and lifted a few days later, when the attached pests can be destroyed.
Lily leaf beetle (Red Lily Beetle)
Long prevalent and withstanding in Europe, the lily leaf beetle (Lilioceris lilii) or Red Beetle has been reported in eastern North America, the eastern and Northern U.S., and eastern Canada. The larvae and adult beetles feed on the leaves of lilies and other liliaceous plants, including Convallaria (lily of the valley) Fritillaria. Both life stages have exceptionally voracious appetites and can devour entire plants within two hours!
The larva is a humpbacked, dirty yellow grub with a dark head, repulsively covering itself in dark, slimy excrement. Yuk! The adult is up to 8 millimeters (0.25 inch) long and bright scarlet with black legs and antennae. The eggs are laid on the underside of the foliage. The following controls are effective… Sorry, but the best and most effect control is with chemicals:
- Spray plants and soil with contact and systemic insecticides; both are effective. Products containing neem (Bon-Neem, Azatin), a botanical insecticide, have been shown to kill very young larvae but must be applied every five to seven days after egg hatch. Products containing the systemic imidacloprid are providing effective control applied either as a foliage spray or soil drench depending on label instructions. Imidacloprid is the active ingredient in Marathon and Merit and one of the active ingredients in Bayer Advanced Rose and Flower Insect Killer for home gardeners. Products containing spinosad, a microbial insecticide, are effective on larvae. Spinosad is sold as Conserve and Entrust for commercial growers and Monterey Garden Insect Spray, BULLâ€™S-EYETM and others for home gardeners.
- Drench soil with an insecticide such as Orthene (e.g.,acephate) to kill the mature larvae that live just under the soil surface in winter. Also, avoid transporting infested soil to other sites.
- Inspect and beware of imported bulbs.
- Catch adult beetles between the fingers and smash them.
The adult lily thrip (Liothrips vaneeckii) is very tiny and black in color. The larva is salmon pink and minute. The adults and larvae live out their entire life cycle in the bulb. Feeding seems to be localized at the bases of the scales, where it seriously weakens the bulb, rendering it flabby. This allows the entry of bacteria and fungi, frequently resulting in the bulb rotting away.
The following controls can be used:
- Treat bulbs with hot water treatment at 44Â°C (111Â°F) for one hour to eradicate the pest.
- Dust bulbs with benzene hexachloride (BHC).
- Wash or dip bulbs in a solution of an insecticide such as Orthene, mineral oil, Neem, Marathon or Merit.
The lily weevil (Agasphaerops nigra) is a native of western North America from northern California to Vancouver Island. It has been reported both on native lilies of that region and on cultivated forms of Lilium longiflorum (Trumpet and Easter lily).
The larvae are minute, whitish, legless grubs with chestnut-brown heads. They burrow into the lily stem and bulb. Adult weevils emerge in March and April, feeding on the leaves of plants.
Systemic insecticides, such as Orthene, Merrit, or Marathon are highly effective in controlling weevils.
Many species of nematodes or eelworms inhabit soils everywhere, regardless of region or zone, and can only be detected or seen with a microscope. Some are harmless or even beneficial to plants, but others are destructive. The most harmful to lilies are the root lesion or meadow nematode and the leaf-lesion nematode. These microscopic pests cause serious damage to lily crops in some regions if their populations are not under control.
Nematodes penetrate root tissues, killing cells as they go. They move inside the root, feeding, laying eggs, and destroying additional cells. The roots become soft and flabby, eventually succumbing to infection that moves into the basal plate, turning it into mush.
River water often carries nematodes, which can then enter croplands through irrigation. These pests also host bacteria; some species even carry virus diseases. Nematode infestation causes stunting of growth and can severely reduce commercial production. Crops parasitized by nematodes are seldom uniformly affected.
Foliar nematodes live in the soil. When a suitable host is present, they move through the stem in a surface film of moisture to invade the leaves and flowers.
The following controls are used for nematodes:
- Keep the foliage as dry as possible to control foliar nematodes by preventing movement of the organisms. Systemic insecticides are very effective.
- Treat bulbs with hot water at 44Â°C (111Â°F) for one hour.
- Fumigate soil with methyl bromide, chloropicrin, and Vapam (e.g., Metamsodium). This is a highly successful technique in commercial plantings, but may not be suitable for the home gardener. Very dangerous stuff, here! Steam sterilization of greenhouse soils is very important.
- Avoid planting lilies continuously in the same site; this prevents harmful nematode populations from building up in the home garden.
- Apply a granular nematicide such as Nemacur fenamiphos (e.g., fenamiphos) when planting bulbs.
- Try adding carnivorous nematodes to the soil.
Pheasant and quail
These birds can develop the habit of pecking emerging shoots in very early spring. They may also peck down to destroy bulbs during cold periods when other food is scarce. Control should be restricted to trapping or shooting the birds only when damage is severe. Poison grains are strictly outlawed in most areas and should never be used to control pheasants and quail. There are other methods…try placing a bucket or some other sort of covering over the bulbs.
Mice and voles often devour lily bulbs, especially when their populations are poorly controlled by animal and bird predators. Moles do not eat vegetation, their diet consists of grubs and worms. If moles are active in an area, mice and voles often use the mole tunnels to get access to bulbs. Traps and poison baits are effective controls; in the home garden, a predatory cat or dog can be of great service.
Squirrels and chipmunks sometimes learn to prey on garden bulbs. The best control is to plant bulbs some distance from trees, since these pests do not like to venture far from the safety of their homes.
Several species of gophers are serious pests in lily plantings in western North America. They love all bulbs and can devour great numbers in a season. Trapping is the most effective way of controlling gophers.
Slugs and snails
These hermaphroditic mollusks lay clusters of round, white, jelly-like eggs in little niches in the soil. Slugs are actually beneficial when populations are not at epidemic levels, as they feed on decaying wood, leaves, etc. When becoming a problem, they can be destroyed by frequent cultivation of the top few inches of soil, bringing the eggs to light and exposing them to frost and birds.
Slugs in particular can be a problem both above and below ground, depending on the species present. They find harbors in moist, shaded areas under dead leaves and other plant debris or among low-growing plants. They are particularly prevalent during rainy seasons.
Slugs and snails feed voraciously on lilies when the shoots emerge. Later in the season they can climb the stems, stripping the leaves completely.
To control slugs and snails:
- Limit habitat around lily plantings by controlling weeds and using mulch instead of ground cover planting.
- Place bait containing metaldehyde among plantings in the early evening hours. This is crucial at the time when lily shoots are emerging and during damp weather. Bait should be renewed after heavy rain, but if you have pets, I would not recommend any baits. However, liquid bait such as Deadline may be less attractive to pets than pelletized bait, but be very careful when baits with pets. Perhaps a safer treatment is beer traps and are used successfully: simply pour the beer into a shallow dish and place it near the lily plantings in the early evening. Pets like it, too and if you see your dog or cat kind of walking sideways, well…
These tiny, almost microscopic insects are prevalent in some soils and can be extremely difficult to eradicate. They can damage lily crops severely if their populations get out of control. The tiny creatures are barely visible to the naked eye; they are best diagnosed by submitting a soil sample to an agricultural laboratory. The usual control is soil fumigation and I do not recommended this for the home gardener. Instead, if these critters have been correctly diagnosed as a problem, I would recommend removing the bulbs and keeping the soil tilled or disturbed for a few weeks. Exposing them to light will usually eradicate the problem.