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Magnolia Scale Diagnostic Guide

Neolecanium cornuparvum

Magnolia scales, Neolecanium cornuparvum, are amongst the largest scale insects to infest shade trees, with some individuals reaching ½” in length. A conspicuous pest in mid to late summer, they cause damage to trees by weakening and girdling branches while producing sticky ‘honeydew’ on leaves and targets below.stressed tree.

Trees at Risk

Star Magnolia (Magnolia stellata), Saucer Magnolia (Magnolia soulangeana), Cucumbertree Magnolia (Magnolia acuminata), Lily Magnolia (Magnolia liliiflora). It has also been reported on Daphne spp., Virginia Creeper (Parthenocissus quinquefolia), Tuliptree (Liriodendron tulipifera).

Star Magnolia

Saucer Magnolia

Cucumber Tree

Lily Magnolia

Tuliptree

Signs of Magnolia Scale

Signs of Damage

  • Sticky honeydew on leaves and targets underneath the infested tree.
  • Dwarfed or stunted growth on infested twigs.
  • Branch decline on severely infested twigs.
  • Presence of large, oval-shaped dark brown insects on twigs and branches, often in high population numbers in late spring/early summer.
Signs of Magnolia Scale

photo: MSU.edu

Signs of Magnolia Scale

photo: WikiCommons

Treatment Strategy

Magnolia scale can be a challenging soft scale to control. Reports from arborists and university scientists have yielded inconsistent control from both crawler sprays and soil-applied systemic treatments. The magnolia scales non-synchronized (crawlers hatch and settle for a prolonged period of time in late summer/early fall) life cycle makes the timing of spray products operationally challenging.

  • Soil Application using Xytect 2F

    Dosage: 6ml/inch of DBH
    Timing: Xytect soil applications should be applied in the spring or in late summer/early fall of the previous year to kill next year’s crawlers. Apply summer sprays to crawlers at 2155-2800 GDD.
    Re-Treatment: Annual
    Xytect 2F
    Xytect 2F
    $69.60
  • Foliar Spray using Xytect 2F

    Dosage: 45 ml / 100 gal of water w/ 0.5% RTSA Horticultural Oil
    Timing: Xytect soil applications should be applied in the spring or in late summer/early fall of the previous year to kill next year’s crawlers. Apply summer sprays to crawlers at 2155-2800 GDD.
    Re-Treatment: Annual
    Xytect 2F
    Xytect 2F
    $69.60
  • Soil Application using Xytect 75WSP 22 packets

    Dosage: 1 packet / 24 inches of DBH
    Timing: Xytect soil applications should be applied in the spring or in late summer/early fall of the previous year to kill next year’s crawlers. Apply summer sprays to crawlers at 2155-2800 GDD.
    Re-Treatment: Annual
    Xytect 75WSP 22 packets
    Xytect 75WSP 22 packets
    $148.00
  • Foliar Spray using Xytect 75WSP 22 packets

    Dosage: 1packet / 300 gal of water w/ 0.5% RTSA Horticultural Oil
    Timing: Xytect soil applications should be applied in the spring or in late summer/early fall of the previous year to kill next year’s crawlers. Apply summer sprays to crawlers at 2155-2800 GDD.
    Re-Treatment: Annual
    Xytect 75WSP 22 packets
    Xytect 75WSP 22 packets
    $148.00
  • Soil Application using Transtect

    Dosage: 1 packet / 5 inches of DBH
    Timing: Late spring/early summer – June/Early July for soil applications. Apply summer sprays to crawlers at 2155-2800 GDD.
    Re-Treatment: Annual
    Transtect
    Transtect
    $326.00
  • Foliar Spray using RTSA Horticultural Oil

    Dosage: 128 -256 oz./ gal of water
    Timing: Apply summer sprays to crawlers at 2155-2800 GDD.
    Re-Treatment: Annual
    RTSA Horticultural Oil
    RTSA Horticultural Oil
    $39.00
  • Foliar Spray using Up-Star Gold

    Dosage: 21.7 fl. oz. / 100 gal of water w/ 0.5% RTSA Horticultural oil
    Timing: Apply summer sprays to crawlers at 2155-2800 GDD.
    Re-Treatment: Annual
    Up-Star Gold
    Up-Star Gold
    $33.33
  • Foliar Spray using Orthene TT&O WSP

    Dosage: 2/3 lb. / 100 gallons of water with .5% RTSA Horticultural oil
    Timing: Apply summer sprays to crawlers at 2155-2800 GDD.
    Re-Treatment: Annual
    Orthene TT&O WSP
    Orthene TT&O WSP
    $15.20

Treatment Strategy Expectation

  • Heavy magnolia scale populations will require two years of systemic soil treatments to reduce adult feeding and sooty mold production.
  • Expect some adult feeding and sooty mold production in year one, if spring applications of Transtect or Xytect are applied.
  • A combination approach to a systemic soil treatment and a fall crawler stage foliar spray may be used to provide additional control of heavy initial scale populations. As scale population is reduced in following years consider applying a stand-alone soil treatment of Transtect in early spring or Xytect in late fall.
  • Since the females leave their hollow brown shells behind that stick to the plant for many months, check to see if scales are alive by crushing the shell. Live scales will “bleed” when crushed, dead scales will be dry and will not “bleed”.

A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org

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