Flat Mites (False Spider Mites)

Flat mites are extremely small and difficult to detect with the naked eye. Adults are typically 200–300 micrometers in length, making them comparable in size to broad and cyclamen mites. Unlike true spider mites, flat mites are slow-moving and do not produce webbing. They are most often found on the underside of leaves, particularly along the main veins.

Damage caused by flat mites can be difficult to diagnose. Feeding results in brown, scabby discoloration that spreads outward from the leaf veins into the leaf blade. Over time, this damage can lead to premature aging of leaves, reduced plant vigor, and in some cases misshapen growth, likely due to toxic substances secreted during feeding. Because symptoms may resemble nutrient or physiological disorders, correct identification is critical.

What to look for:
Brown or scabby discoloration along leaf veins, mottling or bronzing of leaves, premature leaf aging, and collapsed or necrotic patches in areas of feeding.

Life Cycle of Flat Mites

Flat mites undergo a multi-stage development cycle typical of plant-feeding mites.

Egg – Eggs are laid on the underside of leaves or in protected plant areas.
Larvae – Larvae hatch with three pairs of legs and begin feeding immediately.
Nymphs – Nymphal stages resemble adults but are smaller and not yet sexually mature.
Adults – Adults are flattened in appearance, slow-moving, and continue feeding on leaf tissue.

The duration of each life stage is strongly influenced by environmental conditions such as temperature and humidity.

Biology of Flat Mites

Flat mites (Tenuipalpidae) have a worldwide distribution and are found on a wide range of cultivated plants, particularly greenhouse ornamentals and perennial crops.
They are commonly referred to as “flat mites” due to their flattened body shape compared to other plant mites.
Most damaging species belong to the genus Brevipalpus, including Brevipalpus phoenicis, Brevipalpus obovatus, and Brevipalpus californicus.
Flat mites feed primarily on the underside of leaves, often near the main veins.
Unlike true spider mites, flat mites do not produce webbing, which can delay detection.
Several Brevipalpus species are known to transmit plant viruses, increasing their economic importance.

I see flat mites, now what?...

Biological control options are available for flat mites. Predatory mites such as Neoseiulus californicus can be used as part of a biological control strategy. Repeated introductions may be necessary depending on pest pressure and environmental conditions.

Because flat mites do not produce webbing and tend to remain localized along veins, early intervention is important to prevent damage from becoming widespread.

I don't see any flat mites, but I'd like to act preventatively....

Preventative biological control can be implemented using slow-release systems such as sachets, which allow predatory mites to emerge over an extended period. These systems help maintain a background population of natural enemies and reduce the risk of flat mite establishment.

Environmental conditions, crop type, and the presence of other pests will influence predator performance. Reviewing predator characteristics and crop conditions is recommended before selecting a biological control strategy.

Additional Notes About Flat Mites

Flat mites are most commonly found on the underside of leaves, especially near major veins.
Because damage may appear before mites are easily detected, nearby leaves without visible symptoms should also be inspected.
The absence of webbing often delays diagnosis compared to true spider mite pressure.