Watch a YouTube video on biological control of spider mites with a predatory mite.
Predatory Phytoseiulus persimilis for Spider Mite Biocontrol
Two- spotted spider mites (Photo 1) are among the most destructive pests in greenhouse and field crops. These tiny arachnids reproduce rapidly, damage plant tissues, These spider mites reproduce rapidly, damage many crops and ornamental plants like cucumbers, tomatoes and roses by piercing leaf cells and sucking out cell sap, causing stippling, yellowing, reduced photosynthesis, webbing (Photo 2), and eventually leaf drop and reduced yields.and quickly develop resistance to chemical pesticides. Fortunately, nature provides an efficient solution: Phytoseiulus persimilis, a specialized predatory mite used worldwide for biological control of spider mites.
What Is Phytoseiulus persimilis?
Phytoseiulus persimilis is a predatory mite (Photo 3) species that feeds primarily on spider mites, especially the two-spotted spider mite (Tetranychus urticae Photo 1). Originally discovered in Chile, it is now commercially mass-reared and widely used in integrated pest management (IPM) programs. Unlike generalist predators, P. persimilis is a specialist, meaning it actively seeks out spider mites as its primary food source. This makes it highly efficient when infestations are present.
Why Use Phytoseiulus persimilis?
1. Rapid Population Growth
Under optimal conditions (20–30°C or 68- 86°F) with moderate humidity), P. persimilis reproduces quickly. Females lay multiple eggs per day, allowing predator populations to increase alongside spider mite outbreaks.
2. Strong Hunting Ability
These predatory mites actively search for two- spotted spider mite colonies. They can detect infestations and move efficiently across plant surfaces to locate prey.
3. Reduced Chemical Use
Using biological control agents like P. persimilis reduces reliance on synthetic miticides. This lowers the risk of pesticide resistance and supports environmentally friendly production systems.
4. Ideal for Greenhouses
Phytoseiulus persimilis performs exceptionally well in protected environments such as greenhouses, tunnels, and indoor growing systems where conditions can be optimized.
How Phytoseiulus persimilis Controls Spider Mites
Phytoseiulus persimilis feeds on all life stages of spider mites:
- Eggs
- Larvae
- Nymphs
- Adults
An adult predator can consume multiple spider mite eggs or several adult mites per day. When prey is abundant, the predator population expands rapidly. As spider mite numbers decline, predator populations naturally decrease, maintaining ecological balance.
Best Conditions for Success
To achieve effective control, consider these environmental factors:
- Temperature: Optimal between 20–30°C (68- 86°F)
- Humidity: Moderate to high humidity improves performance
- Early Introduction: Release at the first signs of infestation
- Chemical Compatibility: Avoid broad-spectrum pesticides that may harm beneficial mites
Regular crop monitoring is essential. Early detection ensures that predator releases occur before spider mite populations explode.
Optimum Release Rates and Application
Release rates vary depending on infestation severity:
- Preventative: 2–5 mites per m²
- Light infestation: 5–10 mites per m²
- Heavy infestation: 20+ mites per m²
Predators are typically distributed directly onto leaves near spider mite colonies. Multiple releases may be necessary for severe infestations.
Crops Commonly Protected
Predatory Phytoseiulus persimilis mite is widely used on:
- Tomatoes (Photo 4)
- Cucumbers
- Peppers
- Strawberries
- Ornamentals
- Cannabis
It is particularly effective in greenhouse vegetable production systems.
Advantages and Limitations
Advantages
- Highly specific to spider mites
- Fast-acting biological control
- Safe for workers and beneficial insects
- No chemical residues
Limitations
- Requires adequate humidity
- Not suitable for preventive use without prey
- Less effective in very hot, dry conditions
Conclusion
Predatory Phytoseiulus persimilis mite remains one of the most successful examples of biological control in modern agriculture. Its precision targeting of spider mites, rapid reproduction, and compatibility with sustainable farming systems make it an essential tool for greenhouse and high-value crop producers. When introduced early and managed properly, this tiny predator can provide powerful, natural protection against one of the most persistent crop pests.