Azalea whitefly, Pealius azalea, is a common pest of azalea in the landscape. It is very similar to other whiteflies in that it lives and feeds primarily on the undersides of leaves. Whiteflies suck out the plant juices causing yellowing of leaves. They also cause a sticky sap like substance, called honeydew, to coat leaves. This honeydew can attract other insects as well as allow black sooty mold to grow on coated surfaces.
Treatment Strategy
Monitoring and catching populations early will help greatly with control efforts. Systemic insecticides are the easiest products to use to control this insect since they feed primarily on the undersides of leaves, making foliar sprays a difficult option. Begin Xytect applications in the fall for next season control. Early spring applications can work but you must get the product applied before nymphs emerge in May. Transtect applications can provide current season control, and should begin in May with the hatch of eggs.
Other Treatment Practices
- Maintain plant health and monitor closely for this insect.
- Adequate water is a key factor in maintaining stress free plants. A slow, deep watering event once every few weeks during dry conditions will help maintain soil moisture levels and minimize stress.
- Mulch is very beneficial for all trees because it reduces competition with turf and moderates soil temperature and moisture levels. The addition of 3 inches of wood chips or shredded bark under the drip line can have a very beneficial effect by holding in moisture and promoting healthy fibrous roots.
- Bag clippings and remove from premises after pruning. This will help lower local populations.
- Inspect all nursery stock upon delivery or installation.
Limb/Foliar Spray or Soil Application Using Transtect
Limb/Foliar Spray or Soil Application Using Xytect 2F
Limb/Foliar Spray or Soil Application Using Xytect 75 WSP
Foliar Spray Using RTSA Horticultural Oil
Foliar Spray Using Proxite + RTSA Horticultural Oil
Expected Results
Systemic insecticides are very useful for controlling this insect.
Signs of Damage
- Small, white, two winged flies emerge as a cloud upon disturbing host plant
- Eggs, nymphs, adults, and skin casts can be seen on the underside of leaves
- Leaves become yellow form whiteflies sucking the sap from them
- Sooty mold will often grow on excreted honeydew on lower foliage
- Leaf margins begin to cup in heavy infestations
Photo: John A. Weidhass
Virginia Polytechnic Institute and State University, Bugwood.org
Photo: Clemson University
USDA Cooperative Extension Slide Series, Bugwood.org
Photo: John A. Weidhass
Virginia Polytechnic Institute and State University, Bugwood.org
Trees At Risk
- Azalea
Biology
- The life cycle consists of an egg 4 nymphal instars a pupal and an adult stage
- Eggs require 10-12 days to hatch
- The first instar nymph is motile, also called a crawler
- Nymphs overwinter on azalea leaves
- Pupae are yellow and lack fringes common to other whitefly species
- Adults emerge in spring and lay eggs on the undersides of leaves
- Up to 3 generations: Gen 1 –448 to 700 GDD, Gen 2 –1250 to 1500 GDD, Gen 3 2032 to 2150 GDD
References
Virginia Tech
http://pubs.ext.vt.edu/444/444-280/444-280.html
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.
