Mites are among the most challenging greenhouse pests due to their rapid reproduction and ability to remain hidden within young plant tissue. Broad mites (family Tarsonemidae) are especially difficult to detect because of their extremely small size and the severe damage they can cause before becoming visible.
What Are Broad Mites?
Broad mites are microscopic pests that infest a wide range of horticultural crops. Unlike spider mites, which prefer warm and dry conditions, broad mites thrive in humid, shaded environments.
- Measure only 0.1–0.3 mm in length.
- Prefer young shoots, growing tips, and developing leaves.
- Can hide in extremely small spaces, making early detection difficult.
- More than 500 species are known, although only a small number are economically important crop pests.
Life Cycle
Broad mites reproduce very quickly, allowing populations to increase rapidly under favorable greenhouse conditions.
- Females are larger than males.
- Eggs are transparent, oval, and relatively large compared to the adult mite.
- Larvae emerge with six legs before entering a non-feeding resting stage.
- The life cycle is approximately 15 days at 15°C and only 5 days at 25°C.
- In heated greenhouses, reproduction may continue throughout the entire year.
Plant Damage
Broad mites feed primarily on the youngest plant tissue and inject toxins while feeding. Plant damage often appears before the mites themselves can be observed.
- Distorted or deformed new growth.
- Twisted, curled, or brittle leaves.
- Dark green foliage, sometimes with a bronze appearance.
- Death of growing points and flower buds.
- Splitting or cracking of developing plant tissue.
- Stunted plant growth and delayed recovery after infestation.
These symptoms are often confused with viral diseases or chemical injury, making accurate diagnosis essential.
How Broad Mites Spread
Broad mites can easily move between plants and facilities through several routes.
- Workers’ clothing, hands, hair, or footwear.
- Contaminated tools and equipment.
- Growing media or plant material.
- Insects such as whiteflies that transport mites between plants.
Many commercial nurseries reduce this risk by implementing strict hygiene procedures, visitor restrictions, and dedicated work clothing.
Monitoring and Early Detection
- Inspect young leaves and growing tips regularly.
- Use a hand lens or microscope, as mites are rarely visible with the naked eye.
- Examine healthy-looking tissue adjacent to damaged leaves, where mites are most likely to be active.
- Act immediately when symptoms first appear to reduce population growth.
Control Strategies
Cultural Practices
- Maintain strict greenhouse hygiene.
- Disinfect tools and equipment between crops.
- Remove heavily infested plant material.
- Limit unnecessary movement between production areas.
Biological Control
- Predatory mites may help suppress broad mite populations.
- Success depends on early introduction and appropriate environmental conditions.
Chemical Control
If chemical control is required, use only products that are approved for the crop and region where they are being applied.
- Because mites rapidly move to new growth, repeated applications may be necessary to interrupt the life cycle.
- Rotate products with different modes of action to reduce the risk of resistance.
- Always follow the product label, local regulations, and manufacturer recommendations.
Best Practices
- Inspect crops frequently, especially new growth.
- Quarantine new plant material before introducing it into production areas.
- Maintain excellent sanitation throughout the greenhouse.
- Respond quickly to the first signs of infestation.
- Integrate cultural, biological, and chemical controls as part of an Integrated Pest Management (IPM) program.
Important Notice
Pesticides and biological control products should always be used according to the manufacturer’s instructions and local regulations. Never exceed the recommended application rates, and always verify that the selected product is registered for the intended crop.