The southern red mite (Oligonychus ilicis) is a type of spider mite that causes significant damage on southern highbush blueberries (SHB) in Florida. Typically seen in the spring and fall during warm dry weather, these mites live and feed on the underside of blueberry leaves. Damage from this feeding can include bronzing of the foliage, decreased photosynthesis, stunted plants, defoliation, and flower and fruit malformation.

Adult southern red mite adults are about 1/64 of an inch (0.4 mm) in length, red or brown to deep purple, with lighter-colored legs (Figure 1). Females are slightly larger than males and have a more rounded body shape. The eggs are red or brown, and hatch into larvae with six legs (whereas adults have eight legs. One generation can be completed within two weeks and several overlapping populations can occur in one year under favorable conditions.

Figure 1. Adult southern red mite

Credits: L. Buss, UF/IFAS

It is important to begin scouting for southern red mites in late August to early September to identify early infestations. Weekly scouting is recommended until late February. Adult mites can be seen with a hand lens. To scout for their presence, closely examine the underside of leaves and look for eggs, nymphs, and adults. Shed white skins (Figure 2) are an indication that mite feeding occurred within the previous week. Infestations typically begin in the lower and middle portions of the canopy and move up as populations increase. Another method to scout for the presence of mites is sharply tapping foliage onto a sheet of white paper to observe any adults. The presence of adults can also be observed by looking for bronzed foliage (Figure 3), although these symptoms generally appear when moderate to severe infestation levels have already occurred and the risk of defoliation has increased.

Figure 2. Southern red mite shed skins on underside of leaf

Credits: D. Phillips, UF/IFAS

Figure 3. Southern red mite feeding damage on blueberry foliage

Credits: D. Phillips, UF/IFAS

When adults are present, appropriate management controls should be implemented, including good cultural practices and miticides. Dusty conditions are favorable for mites, and drought stressed plants can be more susceptible to infestations. Water should be regularly applied to roadways or other dusty areas during hot, dry periods, and plants should be provided with sufficient irrigation to avoid drought stress, which is particularly important during periods of mite activity.  

Predatory mites are an important management tool for controlling mites, although these predators have not yet been successfully evaluated in blueberry systems. Some naturally occurring predatory mites have been found on SHB in Florida, including Amblyseius spp. 

There are three miticides labeled for use in highbush blueberry, Magister® (fenazaquin), Portal® (fenpyroximate), and Kanemite® (acequinocyl). Only one application per year is allowed for Magister®, and two per year for Portal® and Kanemite®. These miticides control all developmental stages including larvae, nymphs, and adults of southern red mites. Data from University of Florida 2019 field trials (where seven miticides were evaluated) indicate that Portal® and Magister® were the best-performing ones in terms of suppressing southern red mite populations and allowing bushes to recover from mite injury. Some Florida blueberry growers have reported success in controlling mites with sulfur, Sulfur-CARB (a sulfur and molasses mixture), and horticultural oils.

For additional information on this pest, see UF/IFAS EDIS Publication ENY-1006, Mite Pests of Southern Highbush Blueberry in Florida (https://edis.ifas.ufl.edu/publication/IN1284) and EDIS Publication HS1156, 2024 Florida Blueberry Integrated Pest Management Guide (https://edis.ifas.ufl.edu/publication/HS380). 

CREDITS

DR. OSCAR LIBURD, UF/IFAS

& DOUG PHILLIPS, UF/IFAS