Tetranychus spp.
Spider mites are a common pest on a host of tree and shrub species. They suck out cell contents, leaving stippling patterns. Spider mites fall within two general categories: cool-season mites, which are generally active in early spring and fall, and warm-season mites, which are generally active during the summer months. Identifying what season the spider mites affecting the target plant are active is key to managing these pests.
Susceptible Hosts
Spider mites are a common pest on a wide host range of tree and shrub species.
Diagnosis
- Determine if mites are active by slapping foliage against a white sheet of paper to observe tiny active mites.
- Yellowing foliage and stippling can be seen throughout growing season.
- Leaf drop.
- Grayish, unhealthy appearance
- Skin casts are sometimes visible on undersides of leaves.
- Some species create a fine web that may coat leaves or needles.
- Damage from cool-season mites may not be evident until hot/dry summer conditions.
Biology / Lifecycle
Cool Season Mites (ex. Spruce and Southern Red)
- Hatch from eggs in early Spring and go through a larval stage and several instars before maturing into adults.
- Up to 8 generations per year.
- Populations fall with onset of temps greater than 85º.
- Eggs overwinter on leaves.
Warm Season Mites (ex. Two-spotted, European Red, Honeylocust, Maple, Oak)
- Female mites become active in Spring and lay eggs.
- Depending on temperature eggs can hatch in a few weeks to 5 days.
- Multiple generations per season.
- Activity decreases and females overwinter with the onset of cool temperatures.
Twospotted spider mite close-up view
Eugene E. Nelson
Honeylocust spider mite eggs and mites
Whitney Cranshaw, Colorado State University
Honeylocust spider mite damage
Whitney Cranshaw, Colorado State University
Treatment Strategy/Expectations
Either summer or dormant applications of Hort Oil applied to leaves are effective. For heavier infestations, miticides may be necessary. Dormant rate is 2-3% (2-3 gallons per 100 gallons of water)
Control is most effective when populations are identified early. Multiple applications of miticides may be necessary. Abamectin 0.15 Select controls adults and nymphs. Bifenamite controls all stages of mite development and is ideally applied before severe damage is done to the plant. Lepitect will control adults and nymphs and will provide 30 days of residual control. Bifenamite is highly effective against mites while being selectively non-injurious to beneficial and/or predaceous mites and insects.
| Product | App. Method | Dosage | Timing | Re-Treatment |
| Foliar spray | 4-8 oz. per 100 gallons of water | When mites are active | 28 days | |
| Soil injection | 10 oz. pckt / 25 gallons of water for 25-50” of DBH or shrub height | Apply 2 weeks prior to expected emergence | 30-45 days as needed | |
| Tree injection | Refer to label | Apply 2 weeks prior to expected emergence | 30-45 days as needed** | |
| Tree injection | 5ml / 2” of DBH | Apply 2 weeks prior to expected emergence | 30-45 days as needed** | |
| Abamectin 0.15 Select + Hort Oil | Foliar spray | 4oz. Abamectin 0.15 Select + ½ - 1% Hort Oil / 100 gallons of water | When mites are active | 7 days as needed |
* Product is Rainbow Ecoscience’s industry standard recommendation for most industry situations.
**Generally, it is not recommended to perform tree injection on the plant more than once per season.
Reach out to Rainbow Ecoscience Technical Support for additional protocol support.
Trunk injection with Quantum
Soil application with HTI 2000
Foliar spray with Maruyama
Always refer to product label for rates and approved uses. Some images courtesy of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments.
