False oleander scale (FOS) can be a serious pest of southern magnolia, palms, and aucuba. The biology of FOS is somewhat of a mystery. The most commonly targeted stages for management are females and crawlers (mobile baby scales). When killed, the armor covering on females will continue clinging to the plant. Therefore, you have to lift the covering to determine if the scale is dead or alive. If you see a bright yellow blob under the scale, then it is alive; however, a brown and dry scale means it is likely dead. Last year, we counted the number of live FOS females with and without eggs on infested Aucuba. We carefully lifted the covering of thousands of scales under the microscope to check life states. Our efforts were rewarded with some important results that might lead to better management tools.
- All life stages peaked in mid-July and in mid-November.
- Crawler dispersal and predators likely contributed to sharp declines following these peaks.
- Winter and spring peaks in live females may be times when predators are less active.
- Early August had the greatest percent of females with eggs (45%)
- The fewest number of females with eggs occurred in late January through mid-March.
These results lead us to believe there are benefits to an insecticide application in spring (January to mid-March). In the early spring, populations of scales are low. Additionally, there are fewer eggs, and 50-70% of females are alive. Horticulture oils are efficient at killing females and are safer for beneficial insects. Using a second application of oil in June may help reduce the July population peak. This year, we are working on comparing horticulture oil to an insecticide. This will involve monthly applications from April through July. To try and reduce spring FOS populations, we will investigate a monthly application from October to January. This will target females with low egg counts. You don’t have to wait on our results if you want to give it a try this year. If you do, let us know what you think.
The lab at Auburn University conducts research on pests of turfgrass and ornamentals in landscapes and in production. For more information on the biology and management of scale insects and mealybugs, consult your regional Extension agent or read more at Common Insects and Disease Pests of Turfgrasses and Ornamentals, ANR 910 and Controlling Scale Insects and Mealybugs, ANR 2423. The Southeastern US Pest Control Guide for Nursery Crops and Landscape Plantings is also an excellent resource.