Gadenin日本語Get the appThe red beetle is the one that matters
It is about a third of an inch (8 mm) long, brilliant scarlet with a black head and legs, and it is impossible to confuse with anything else on a lily. The adults overwinter in soil and leaf litter, often nowhere near the plants, and they arrive on the shoots the moment those shoots break ground in spring. They eat the leaves, then the buds, then the stems. A single plant can go from full and healthy to a chewed bare stalk within a few days, and once the leaves are gone the bulb has no way to feed itself for the rest of the year.
The larvae do most of the damage and are far harder to spot, because they coat themselves in their own wet black excrement. What you see on the underside of a leaf is a slimy dark blob rather than an insect, and gardeners routinely mistake it for bird droppings or dirt. Under it is a fat orange grub eating steadily. By the time you notice a stem covered in these, the plant is usually half stripped.
The eggs are the earliest sign and the easiest thing to remove. They are laid in short lines of small orange sausages along the underside of the leaves, usually low on the plant. Rubbing them off with a thumb takes seconds and prevents a whole generation of larvae. Any inspection of a lily should turn a few leaves over rather than just looking at the top.
The adult beetle drops off the plant the instant it feels a vibration and lands on its back, where its black underside makes it nearly invisible on soil. Hold a hand or a tub under the leaf before you reach for it.
Hand picking, done properly
There is no shortcut. Check every lily every day or two from the moment the shoots appear until the stems die down in autumn, and pick off what you find. This sounds tedious and it takes about a minute per plant, and it is the difference between full stems in flower and bare sticks in early summer. Two beetles removed in early spring are several dozen larvae not eating your plants in early summer.
Work in the middle of the day when the adults are active and on the upper leaves. Cup one hand or hold a small tub of soapy water directly beneath the beetle, then touch it from above; it drops straight into your hand or the water rather than escaping into the soil. Crush the adults or drown them, and squash the larvae in place with a gloved thumb or wipe the leaf clean with a cloth.
Turn over the lower leaves on the same visit and rub off any lines of orange eggs. Then look at the soil surface around the base of the plant, where beetles that dropped earlier are often sitting, and check nearby lilies, since they move between plants readily.
Cutting down the dead stems and removing the debris in autumn, rather than leaving it as overwintering shelter, reduces the number that start in your own beds. It will not eliminate them, since adults fly in from elsewhere.
- Start the day the first shoot shows The adults find lilies immediately on emergence. Waiting until the plant looks worth protecting means the first generation of eggs has already been laid.
- Check the undersides of the leaves, not just the tops Eggs sit in orange lines on the underside and larvae hide there under their black coating. A quick look from above misses both until the damage is done.
- Catch adults from below Hold a hand or a tub of soapy water under the leaf first, then touch the beetle. It drops reflexively and lands upside down on the soil where you will not find it again.
- Wipe off larvae and eggs on the spot Rub the black slimy larvae off with a gloved thumb or a cloth and smear off the egg lines. Both are stationary and cannot escape, so this is quick and completely effective.
- Repeat every two days all season There are overlapping generations through the summer. A single missed fortnight in early summer is enough for larvae to strip a stem and cost you next year's flowers.
The rest of the list
Gray mold blight shows as oval brown or tan spots on the leaves that spread rapidly in wet, humid weather, working up from the bottom of the plant until the foliage collapses. The bulb usually survives but goes into winter underfed. Space plants at least 8 in (20 cm) apart for airflow, water at the base rather than over the leaves, and remove and bin affected foliage and all end of season debris.
Basal rot turns the bottom of the bulb brown and soft and the plant either fails to emerge or produces a weak yellowing stem. It follows waterlogged ground and there is no cure once the basal plate has gone. Deep planting into gritty, well drained soil is the whole of the prevention.
Virus produces mottled or streaked leaves, twisted stems and distorted flowers, and it spreads from plant to plant on aphids. There is no treatment. Dig up and destroy affected bulbs promptly rather than hoping, and control aphids on the remaining plants, because a tolerated virused lily will infect the whole group over a few seasons.
Slugs and snails graze emerging shoots and can take out a young plant entirely in one night. Protect the group for the few weeks the shoots are soft. Squirrels and voles dig up newly planted bulbs; a piece of wire mesh laid over the planting area and removed in spring solves it.
| Symptom | Cause | Action |
|---|---|---|
| Scarlet beetles on shoots and leaves | Adult lily beetle | Pick by hand from below into soapy water, check every two days |
| Wet black blobs on leaf undersides | Lily beetle larvae under their own excrement | Wipe off with a gloved thumb or cloth immediately |
| Lines of small orange eggs under leaves | Lily beetle eggs | Rub off with a thumb, then check the rest of the plant |
| Brown oval spots spreading up the leaves in wet weather | Gray mold leaf blight | Remove affected leaves, water at the base, improve spacing |
| Shoot fails to appear or is weak and yellow, bulb base soft | Basal rot from waterlogging | No cure; replant survivors deep in gritty, free draining ground |
| Mottled or streaked leaves, twisted stems | Virus carried by aphids | Dig up and destroy the bulb, control aphids on the rest |
| Shredded young shoots overnight | Slugs and snails | Protect the emerging shoots for a few weeks in spring |
| Newly planted bulbs dug up and scattered | Squirrels or voles | Lay wire mesh over the area after planting, remove in spring |
Lilies and cats
This belongs on any list of lily hazards, and it is worth stating plainly rather than as a footnote. True lilies are severely poisonous to cats. Every part of the plant is toxic, including the leaves, the flowers, the pollen and the water in a vase that has held cut stems, and a very small exposure can cause fatal kidney failure within a few days.
The pollen is the risk that catches people out. A cat brushing past an arrangement gets pollen on its coat, grooms it off, and that alone is enough. This is why lilies should not be brought indoors at all in a household with a cat, regardless of how high the vase is placed.
If a cat has chewed any part of a lily, licked pollen from its fur, or drunk vase water, treat it as an emergency and get veterinary help immediately. Treatment is effective when it starts early and much less so once symptoms appear. In the garden, plant lilies away from where cats sunbathe or where a neighbor's cat regularly passes, and be aware that the risk exists even for plants that are never cut.
A pest record worth keeping
Write down the date you first see an adult lily beetle each year, and where. That date is remarkably consistent from year to year in a given garden, and after two seasons you know exactly when to begin daily checks rather than reacting once a plant is stripped.
Keep a rough tally of how many beetles and larvae you remove from each group across the season. A group that consistently yields the most is usually the one nearest their overwintering shelter, and it deserves the first inspection each time rather than the last.
Note the date leaf blight appears and how wet the season was. Blight years track the weather closely, and knowing that a bad year was a wet year stops you from digging up bulbs that were never really in trouble.