How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Bulb mites are white with large amber spots, brown legs, and are 0.55 to 0.75 mm long when fully grown. They are slow moving and oval shaped, so are sometimes mistaken for insect eggs. These mites can be found in hollowed out and decomposing portions of bulbs.

DAMAGE

Bulb mites enter the bulb and feed in protected cavities, where fungi and bacteria may cause extensive decomposition of the bulb. They are associated with the spread of Fusarium, Stromatinia, and Pseudomonas diseases of bulbs. Species of bulbs attacked include freesia, hyacinth, lilies, narcissus, and onions, as well as underground peony rhizomes. Freesias are particularly affected because they require high temperature storage to break dormancy, which allows rapid growth of bulb mite populations. Lilies are attacked below ground, which stunts growth. Feeding at ground level causes the plants to topple.

MANAGEMENT

Biological Control
Biological control has not been investigated.

Cultural Control
Bulbs may be disinfested by holding them for 24 hours at 100% relative humidity at 105.5°F. CO₂ fumigation may be useful.

TREATMENT

Thoroughly clean bulbs, dip them in a sulfur fungicide solution, and dry them following harvest. The sulfur will control bulb mites as well as fungal diseases if the bulbs are being held at high temperatures. However, high rates of sulfur may be phytotoxic. Abamectin (Avid), dicofol (Kelthane), some pyrethroids, pyridaben (Sanmite), and endosulfan* (Thionex) are possibly effective, but have not been evaluated.

* Restricted-use pesticide. Permit required for purchase or use.

PUBLICATION

UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
Insects and Mites
J. A. Bethke, Entomology, UC Riverside
Acknowledgment for contributions to Insects and Mites:
K. L. Robb, UC Cooperative Extension, San Diego County
H. S. Costa, Entomology, UC Riverside
R. S. Cowles, Connecticut Agricultural Experiment Station, Windsor, CT
M. P. Parrella, Entomology, UC Davis

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