Magnolia Scale Infestation: A Detailed Examination of This Harmful Pest on Magnolia Trees
Controlling Magnolia Scale in Ohio Landscapes
Magnolia scale, a common pest that infests tuliptrees (yellow poplars) and magnolias, can be a significant threat to the health and appearance of these trees. Here's a guide on effective control strategies for managing magnolia scale in Ohio.
Monitoring and Timing
Timely monitoring is crucial in controlling magnolia scale. The pest's crawler stage typically becomes active around 1938 growing degree days (GDD) in summer, according to pest predictive calendars for regions including Ohio. Regularly inspecting your magnolia trees around mid to late summer allows interventions when scale insects are most susceptible to control measures.
Insecticide Treatments
Systemic or contact insecticides, such as horticultural oils or insecticides labeled for scale insects, are most effective when targeting the crawler stage. Soil-injected insecticides may also be used but are less common and usually require professional application.
Cultural Practices
Maintaining tree health reduces scale damage. This includes proper watering, avoiding excessive fertilization which can encourage scale populations, and pruning heavily infested branches to reduce populations mechanically.
Natural Controls
Encouraging natural enemies such as parasitic wasps and predators can help suppress scales but may not be sufficient for severe infestations.
Integrated Pest Management (IPM)
Combining monitoring, cultural controls, and chemical treatment during crawler emergence offers the best probability of long-term control and limiting damage in ornamental magnolia trees common in Ohio landscapes.
Additional Control Measures
- Dormant oils can be applied in October through November and again in March to kill the overwintering nymphs on stems.
- The magnolia scale spends the winter as tiny, dark-colored nymphs on one- to two-year-old twigs.
- When applied in early May, soil drenches with systemic insecticides have provided excellent control.
- Inspect spring buds carefully as some damage may be caused on the flower buds if they have begun to swell.
Prevention and Early Detection
- Strategy 1: Pest-Free Plants involves careful inspection of branches upon purchase to avoid plants with large scale exoskeletons from the previous season. Most magnolia scale infestations are already present on the tree upon purchase, so careful inspection is necessary.
Impacts of Magnolia Scale
Damage from magnolia scales occurs as they remove plant fluid from their host, leading to weakened branches and twigs, stunted growth, and halting of leaf development. The excess plant sap from magnolia scales is excreted as a sweet, sticky material called honeydew. Black sooty mold, an unsightly dark fungus, colonizes the honeydew and may hinder photosynthesis.
Conclusion
Adult female magnolia scales continue to expand as they feed, turning brownish-purple by early June and yellowish-brown by early summer, covered with a powdery, white waxy coating by late July and August. Adult male magnolia scales are fragile, do not feed, and die after mating. This fact sheet is a revision of HYG-2003.
By regularly monitoring magnolia trees around mid to late summer for crawler emergence, applying insecticides targeted specifically at the crawler stage based on degree day models, maintaining tree health, pruning infested branches as needed, considering assisting natural biological controls through habitat support, and following these strategies, you can effectively control magnolia scale in Ohio landscapes.
Soil-injected insecticides, which are less common and usually require professional application, can be used to target the crawler stage of magnolia scale. To prevent magnolia scale infestations, it's essential to carefully inspect plants upon purchase to avoid introducing infested branches into home-and-garden settings.
