False oleander scale (FOS), Pseudaulacaspis cockerelli (Fig. 1), is an invasive armored scale species native to China. It is prevalent in Georgia and poses a significant threat as a pest in ornamental nurseries. FOS primarily infests the leaves of plants, appearing as white spots (Fig. 2). As armored scales, they spend their entire lives inserting their tubular, hair-like mouthparts into plant tissue. They do not secrete honeydew; as a result, the leaves do not become coated with sooty mold fungus. The second and third nymphal stages and adults of FOS secrete wax that forms a protective shell covering. This shell can detach from the scale’s body. The size of the female scale may vary depending on the host species. Unlike other insects, FOS lacks legs, eyes, and antennae.
Life cycle
FOS undergoes several generations each year. Crawlers are the only mobile stage of FOS, emerging from mid-April to early May. Adult females, measuring less than 1/8 inch long (2-3 mm), are typically found on the upper surface of leaves beneath flat, pear-shaped shell coverings (Fig. 4). The pointed end of the female is yellowish-brown (Fig. 4). Males are located on the undersides of the leaves and appear elongated (approximately 1 mm), featuring three elongated ridges and snowy white coverings. Males tend to cluster together. A female lays about 20 eggs within the shell covering. The eggs are oval-shaped and yellow (Fig. 3). Crawlers emerge from the eggs within 2-3 days during the summer. They move away from the female, wander randomly, and settle on the leaf surface after inserting their hair-like mouthparts to feed on plant sap. People, animals, birds, ants, and wind currents typically disperse crawlers. Once settled, they molt into the second instar, shed their legs, and begin secreting shell coverings (Fig. 4). Generally, the period from egg to adult takes about a month in the summer.
Host plants
FOS has a wide host range, as it can infest over 100 plant species. It is commonly found in landscapes in the southern magnolia (Magnolia grandiflora). Other common hosts include aucuba (Aucuba japonica), boxwood (Buxus sempervirens), oleander (Nerium oleander), banana shrub (Magnolia figo), sago palm (Cycas revoluta), cycads (Cycas spp.), gardenia (Gardenia jasminoides), English ivy (Hedera helix), bischofia (Bischofia javanica), camellia (Camellia japonica), and palmetto (Sabal palmetto).
Damage
The affected leaves will develop yellow or chlorotic spots (Fig. 5), resulting in delayed growth and development. As the population size increases, the leaves drop, causing stunted plant growth. FOS typically remains on older foliage.
Management
When introducing new plant material from other nursery facilities, inspecting for FOS infestations before integrating it with the existing nursery stock is crucial.
All stages of FOS can be found in the summer. Contact insecticides, such as pyrethroids, insecticidal soap, and horticultural oil, are effective only on the crawlers. Managing FOS can be challenging when using contact insecticides because they are less effective against nymphal stages and adults, except for crawlers, due to their waxy shells. Crawlers do not have shell coverings. Multiple applications of contact insecticides with adequate coverage are necessary to reduce the population during the summer.
Soil application of systemic insecticides containing dinotefuran (Safari or Zylam) and thiamethoxam (Flagship) in the crown area of the plant or tree can reduce the FOS population. The insecticide residues quickly move through the soil and reach the root system. The roots absorb the residues from the soil and rapidly transport them through the vascular bundles to the leaves, where FOS are fed. They ingest insecticide residues, leading to scale mortality.
Foliar application of imidacloprid also reduced nymph populations eight weeks after treatment. Dead scales remain on the foliage. Additionally, foliar applications of insect growth regulators, such as pyriproxyfen (Distance) and buprofezin (Talus), can suppress FOS populations for up to twenty-eight days.
References
Buss EA. 2004. False oleander scale control, 2023. Arthropod Management Tests 29 (1): G40, https://doi.org/10.1093/amt/29.1.G40
Carson KMH, Carroll E, Ibiyemi O, Byrd WB, Thurmond A, Vinson A, Sullins K, Held DW. 2021. Efficacy of foliar sprays of various products against false oleander scale on potted Aucuba japonica, 2019. Arthropod Management Tests 46(1): tsab123. https://doi.org/10.1093/amt/tsab123
Beardsley JW Jr, Gonzalez RH. 1975. The biology and ecology of armored scales. Annual Review of Entomology. 20: 47-73.
Hamon AB, Fasulo TR. 2021. False oleander scale, Pseudaulacaspis cockerelli (Cooley) (Insecta: Hemiptera: Coccoidea: Diaspididae). IFAS Extension, University of Florida, EENY-149. doi.org/10.32473/edis-in306-2000
