Lilies are hardy plants that are relatively easy to grow. But some, several diseases and pests can present challenges to that goal.
Aphids
Aphids are a common pest of many plants; unfortunately, lilies are no exception. They reproduce rapidly in the spring then the offspring begin to feed on any plant nearby.
Their tiny bodies are visible on the leaves and can be easily washed off with a hose. However, other measures may be called for when they reach a specific population density.
Insecticidal soaps are one easy, low-impact way to control them. There are commercially available systems that go a step beyond and not only kill but help prevent aphids.
A systemic is a chemical that is added to the soil. The plant takes it up, and when the aphid sucks the sap, it ingests the lethal pesticide simultaneously. Systemics do not harm the plant.
Aphid control is significant since not only can they destroy a single plant, but they may spread viruses. Viruses invade individual cells, and the aphid consumes them when it feeds.
But some remains on the outer parts of the aphid where it can be implanted onto the next plant the aphid visits.
Lily Beetle
Beetles are another common garden problem, and one, particularly that likes lilies: the aptly-named Lily Beetle (Lilioceris lilii). A relatively recent immigrant from Europe, it is easy to spot. It has a bright red upper body about 1/4″ inch long and a black belly.
The larvae are orange. Both the adult and offspring feed on lilies, with the larvae clinging to the underside of leaves.
Brushing them off is usually of limited benefit since they can crawl back up again, and catching them in a bowl is iffy. They appear to have no natural predators in North America, so chemical control is usually best.
Neem oil is one safe way to control them. It is applied to the plant once per week, kills larvae, and repels adults. A systemic chemical called Merit has shown promising results, too. It should be applied to the soil in early spring.
Viruses
Viruses kill by invading the cells of plants and co-opting their reproductive mechanism, then bursting the cell wall when they reproduce. This gradually destroys the plant. Evidence of viral invasion shows as streaking or mottling on leaves, weak growth, and smaller than typical plants.
The common Cucumber Mosaic Virus is a good example. It doesn’t just invade cucumbers but infects lilies regularly. The leaves then become brittle and distorted.
Controlling or preventing viruses is difficult. Once infected, unless the plant can recover on its own through natural mechanisms, it is best to destroy the plant to prevent spread. Soaking garden tools in bleach is essential to avoid spreading the virus from one plant to the next.
Fungi
Basal rot is the most common fungal invader of lilies. It tends to invade the bulb and eventually destroy it, which naturally kills the plant.
Botrytis attacks the leaves and stem, which is almost as severe. Both showed up as yellowing of leaves and dried stalks, and over-watering is the most typical method of encouraging their growth.
Once they attack, an anti-fungal compound is called for. Even then, though, unless stopped early, it is often fatal. The best treatment is prevention through proper Lily plant care.
Fortunately, safe, practical, and easy-to-apply controls exist for nearly all lily diseases and pests.
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