The oak spider mite (sometimes called the oak red mite) is not an insect, but an insect relative more closely related to the spiders. This species of spider mite is native to New England, but found as far south as North Carolina and west to Kansas. Oak spider mites are dark reddish brown in color, similar to the southern red mite (O. ilicis). Oak spider mites lay their red, barrel-shaped eggs on the surface of leaves in the summer, and in the fall around the axils or crevices of the twigs. Eggs are the overwintering life stage for the oak spider mite. While a precise life cycle for the oak spider mite may not be fully understood, in general spider mites go through similar life stages. In days to weeks, the eggs hatch and the larva emerges. Spider mite larvae are round bodied with only 3 pairs of legs. Larvae feed, molt, and form the first nymphal stage which will possess 4 pairs of legs. At least two nymphal stages typically occur (two molts) after which the adult is formed. Adult females tend to be larger than the males, with rounded abdomens compared to the pointed abdomens of the males.
The upper surface of the leaves of oaks, especially red oaks, are fed upon by this species of spider mite. The oak spider mite causes a bronzing or bleaching of the upper leaf surface, which may be very apparent by June. However, the damage caused by this insect relative is often not noticed until it peaks, usually by late July or early August. Feeding damage may be most concentrated around the leaf midrib. The severe bronzing is most visible on the lower branches of larger trees. Damaged leaves may appear a dull, yellow color, but once the leaf dries out it becomes tan in color. Damage may increase with an increase in temperatures, as well as an increasing amount of impervious surface around the base of the tree (Steven Frank, NC State Extension, 2018).
Monitor susceptible hosts in May and June, and look for the beginning of spider mite activity that may become more severe as seasonal temperatures rise. Scout the lower branches of larger host trees first, as they may be the first to be impacted, particularly those growing in hotter locations (ex. near impervious surfaces such as paved areas).
Trees suffering drought stress should be provided with adequate watering to reduce the impact of spider mite feeding. Do not over fertilize trees infested with spider mites or piercing-sucking insect pests, as this can benefit the pests more than the tree itself. Syringing, or spraying mite infested foliage with a heavy stream of water, may help knock the spider mites off their host and provide management on ornamental/specimen trees or shrubs. If done on a regular basis, syringing can have the same effect as strong rain events which help dislodge the mites and reduce the severity of their feeding.
Lacewings and lady beetles are known to feed on pest spider mite species. Some predatory mite species may be commercially available to manage plant pest spider mites, however the predatory mites that impact the spider mite may be species specific. Phytoseiulus spp., Amblyseius spp., or Metaseiulus spp. are three common genera of predatory mites that are often sold for pest management purposes.
Abamectin (NL)
Acephate (NL)
Beauveria bassiana (NL)
Bifenthrin (NL)
Chlorpyrifos (N)
Chromobacterium subtsugae (NL)
Cypermethrin (NL)
Etoxazole (N)
Fenazaquin (NL)
Gamma-cyhalothrin (L)
Hexythiazox (NL)
Horticultural oil (L)
Insecticidal soap (NL)
Lambda-cyhalothrin (L)
Malathion (L)
Metarhizium anisopliae (robertii) (NL)
Neem oil (NL)
Spinosad (NL)
Spiromesifen (L)
Tau-fluvalinate (NL)
The eggs of this spider mite may be exposed enough that dormant oil applications may be effective (Johnson and Lyon, 1991).
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), and neem oil (soil drench).
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
