Magnolia Scale (Neolecanium cornuparvum)
GDD Window (base 50): 2155-2800
Overview:
- These scales emerge in August and September rather than June & July, as most other soft scale species
- By mid-September, the scales have been undergoing crawler emergence for about a month (Only one generation per year)
- Both scales are found exclusively on woody tissues during all life stages
- Large mature females use their piercing sucking mouthparts to withdraw large quantities of sap from the phloem and exude honeydew that grows sooty mold (attracts ants, wasps, bees & other vespids)
- Causes yellowing leaves and premature leaf drop & branch decline
- Largest soft scale in North America
- Oval, & convex in shape, yellow-brown & about 1/2-inch diameter as mature females
- Young females are covered with a white powdery wax
- Crawlers seen ~ 1 wk after Tulip Tree scales
- 1st instar crawlers are visible without a magnifying hand lens
- Overwinter as large, dark colored, 2nd- instar nymphs on 1–2-year-old wood
- Host plants: host-specific to the magnolia trees only
Management:
Cultural Practices:
- Natural predators: ladybeetles, lacewings, parasitoid wasps
- Use double-sided sticky tape to monitor
- Reduce plant stress
- Prune heavily infested branches
- Regularly monitor for proper timing of controls
- Control ant populations
- Ants will often protect soft scales because they use honeydew as a food source
Materials:
- Contact insecticides:
- Pyrethroids [3A]: -thrins
- Carbamates [1A]: Carbaryl
- Systemic insecticides:
- Neonicotinoids [4A]: imidacloprid, dinotefuran
- Organophosphate [1B]: Acephate (translaminar)
- Considerations:
- Can harm non-target species-
- Unsightly appearance of sooty mold often causes people to apply treatments too early
- If sprays are applied too early, previously laid eggs may have been protected under the female bodies and may still hatch
- Sprays can be applied during the crawler period but may require multiple treatments
- Sprays can be delayed until mid-October to target vulnerable 2nd instar nymphs
Biorationals:
- Horticultural oils or insecticidal soaps will provide good efficacy against 1st or 2nd instars
- Against crawlers, multiple oil/soap applications may be required
Disclaimer – Materials do not cover all possible control scenarios and are intended for licensed professionals. Tradenames do not imply endorsement and are used as examples. You must strictly follow the label for each compound prior to use. Rutgers is not responsible form is used materials or damages thereof. The label is the law. Labels will provide detailed information on use and restrictions. Additionally, application intervals, compatibility, surfactant use, PHI, PPE, important and other key information is described in detail. Always discuss treatments with your local agents. Note: Neonicotinoids can only be legally applied in commercial agriculture settings by licensed applicators. Guidelines and recommendations made in this presentation are specific to the state of New Jersey.