Tulip or narcissus bulbs may emerge stunted or twisted, or fail to emerge at all. When you dig one up and find it soft and crumbling, bulb mites are a common reason.
Bulb Mites: What You See
Most of the signs show up on the bulb and the growth above it, so you often need to dig one up to be sure.
- Shiny, creamy white bodies with short legs, often described as pearls with legs, cluster under the scales and at the base of the roots.
- Each mite measures only 0.02 to 0.04 inches and moves very slowly, so a hand lens helps.
- The bulb is soft, brown, or turning to pulp, because mites open the outer skin and let rot in.
- New growth comes up stunted and distorted.
- Tiny white oval eggs sit alone or in clusters near damaged, decaying tissue on the bulb surface.
On lilies, the stems can be dwarfed and distorted too, and the plant may not survive.
From the almanac
Bulbs in your state
The dates on this page depend on where you live. Your state's page carries its frost dates, its USDA zones and the year laid out month by month.
Northeast
Southeast
- Alabama
- Arkansas
- Delaware
- Florida
- Georgia
- Kentucky
- Louisiana
- Maryland
- Mississippi
- North Carolina
- South Carolina
- Tennessee
- Virginia
- West Virginia
Midwest
Southwest
West
Pacific Northwest
Canada
Bulb Mites or Something Else?
Stunted shoots and mushy bulbs have more than one cause, so a single clue is not enough. Check the plant above ground and the bulb below it before you decide anything.
| Looks like | How to tell them apart |
|---|---|
| Root rot from fungus | Root-rotting fungi can be present with bulb mites, so finding one does not rule out the other. |
| Fungus gnat larvae | Fungus gnat larvae can injure bulbs that bulb mites later infest, so both pests may be present. |
The catch is that these problems often travel together. Bulb mites are secondary pests that tend to move into bulbs already hurt by fungus gnat larvae or root rot, so finding mites does not rule out the others.
What Causes Bulb Mites, and Where It Is Worst
Bulb mites live on decaying vegetation such as weeds and old plant debris, and they have a wide host range. Several generations overlap each year, so a small population can build quickly. They also ride in on infested bulbs, which can carry them into your beds from the start.
Weather plays a part. Injury is worst when cool, wet weather slows plant growth, and mites tend to do more damage in years with cool, wet springs. In Oregon, the highest numbers were present in April and May.
Warmth speeds them up. In Kansas, the life cycle from egg to adult may take about 40 days, but at 77°F (25°C) it can finish in 12 days. In North Carolina, warm conditions bring the full cycle down to about 2 weeks. In Kansas, mites are less active in winter, but they do not rest, and every life stage may be present throughout the growing season.
Bulb mites can show up in any yard that grows bulbs, and they affect amaryllis, crocus, freesia, gladiolus, hyacinth, lily, Dutch iris, narcissus, and tulip.
How to Treat Bulb Mites
Treatment starts with finding out what is happening at the bulb, then removing the source and protecting what is left.
- Dig a few suspect bulbs and look closely at the area where the roots meet the bulb, because that is where mites gather and where they are easiest to confirm.
- Discard soft, rotting bulbs in the trash rather than the compost, so that mites and the fungi they carry do not spread.
- Clear weeds and old plant debris from the bed, since mites overwinter there and move back onto new bulbs.
- Keep sound bulbs away from infested ones, because mites carry pathogens on their bodies and can crawl from one bulb to a healthy neighbor.
- Before planting, soak bulbs in a registered miticide for 30 minutes.
Leave the leaves of healthy bulbs in place until they turn yellow, since they feed the bulb for next year. The aim is to protect sound bulbs from infested ones.
How to Prevent Bulb Mites Coming Back
Prevention focuses on bulb inspection, bed cleanup, and watching early growth.
- Inspect stored bulbs and discard any with soft spots, since infestations affect bulbs in storage as well as in the field.
- Clean out weeds and plant debris from the bed so mites have nowhere to overwinter.
- At planting, choose firm, undamaged bulbs and set them in well-drained soil, so roots are not sitting in the wet conditions that favor rot.
- In early spring, watch for slow or distorted shoots, because damage usually appears early in the growing season and is worse when cool, wet weather slows growth.
- In April and May, check bulbs that look weak, as mite numbers in Oregon were highest in those months.
Keep beds free of weeds and old plant debris, which give mites a place to overwinter.
Where This Comes From
Bulb mites overwinter on decaying vegetation and can infest bulbs in storage as well as in the field.
Common Questions
Can Bulb Mites Hurt Garlic and Onions Too?
Yes. Bulb mites are a problem of garlic that easily goes unrecognized, and they can stunt plant growth and reduce the onion stand.
How Many Eggs Does a Bulb Mite Lay?
In Utah, females lay 50 to 100 eggs in a lifetime, and eggs hatch in 2 to 7 days. Elsewhere, a female is reported to lay up to 100.
Can Bulb Mites Cause Rot on Their Own?
Not usually. By themselves they are not particularly damaging, but if root-rotting fungi are present, the mites injure the roots further and make the rot worse.