Description of the Pest
Citrus flat mites are common pests of pomegranate fruit. Citrus flat mites are very small and difficult to see, even with a hand lens. They are sluggish, translucent, flat, and oblong. Adults have internal spots of red and brown. These mites overwinter under flakes of bark on large branches. They move to the leaves and fruit in summer, with numbers increasing in June, peaking in July and August, and then gradually declining.
Damage
Citrus flat mite feeding results in a brown scabbing or leathering ("alligator skin") of the fruit that looks similar to sunburn. Occasionally, the damage can be quite serious. Mite damage starts at the stem end and the brown discoloration extends further than the cracking. Mites and their cast skins may be found in the cracks. Sunburn and other unknown causes of leathering can be mistaken for flat mite damage. If the fruit surface next to the stem is not damaged, flat mites are not the cause.
Management
Predaceous mites may keep flat mites below an economically damaging level, but most growers use preventive applications of sulfur in early summer. It has not been documented in pomegranate, but in other crops, sulfur can disrupt the natural enemies of other pests (e.g., mealybug and soft scale). However, it is the best control method to prevent flat mite damage.
Biological Control
A predaceous mite has been observed associated with flat mite in pomegranates and likely keeps this pest in check in some orchards.
Organically Acceptable Methods
Some formulations of sulfur are organically acceptable.
Monitoring and Treatment Decisions
Monitor for damage starting in mid to late May by examining the stem end of fruit for scabbing and the presence of flat mites with a high-power hand lens (15–20x) or microscope. If flat mites are present, apply sulfur immediately. A second application of sulfur may be needed in July or August. Sulfur works better in warm weather. Wettable sulfur is less disruptive to predators.
| Common name | Amount per acre | REI‡ | PHI‡ | ||
|---|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | |||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | |||||
| A. | SULFUR DUST 98%# | ||||
| (various products) | 30–50 lb | 24 | 0 | ||
| MODE-OF-ACTION GROUP NUMBER1: un (an inorganic miticide) | |||||
| COMMENTS: Best results are obtained by ground treatments; however, aerial treatments are effective. Use higher rates by air. Check that the formulation you are using is acceptable for organic use. | |||||
| B. | WETTABLE SULFUR | 3–10 lb | 24 | — | |
| (Microthiol Disperss)# | |||||
| MODE-OF-ACTION GROUP NUMBER1: un (an inorganic miticide) | |||||
| COMMENTS: May be applied by ground or air. Check that the formulation you are using is acceptable for organic use. | |||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| # | Acceptable for use on organically grown produce. |
| — | Not applicable. |
| 1 | Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers ("un"=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). |