Soft Scales on Trees and Shrubs

• Mature female covers are oval to hemispherical or irregularly shaped, white to yellowish to purplish-brown, and up to ½” (12.5mm) in diameter.
• Male covers are oval, white, and much smaller.
• Crawlers are black. 

• Magnolias, especially star magnolia (Magnolia stellata), cucumber tree (Magnolia acuminata), lily magnolia (Magnolia liliiflora), and saucer magnolia (Magnolia x soulangiana)

• All life stages will be found on the bark, especially on one- to two-year-old twigs.
• Ants often protect colonies of this scale in order to feed on the honeydew. Examine busy ant trails on young host plants to see if they are tending a population of scale in the canopy.

• Moderate to heavy infestations will produce large quantities of honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
• Heavy or prolonged infestations can cause premature leaf shedding, reduced foliage production, reduced blooming, and potentially branch dieback.

• There is 1 generation per year in Maryland.
• The crawler emergence period depends on temperature and can vary slightly from year to year. The approximate time to monitor for them is September.
• They overwinter on the bark as juveniles.
• Juveniles can be so numerous that they appear to be normal features of the bark. They appear as numerous small, dark ovals on bark.

No local Growing Degree Days and Plant Phenological Indicator data have been compiled for this species.

• Mature female covers are oval, dark reddish-purple covered in white felt, and up to ⅛” (3mm) long.
• Male covers are oval, white, and smaller.
• Crawlers are reddish.

• Prefers azaleas and rhododendrons (both are members of genus Rhododendron) and relative Andromeda/Pieris (Pieris)
• Several other species of flowering shrubs, trees, and evergreens, including ornamental cherry (Prunus), hawthorn (Crataegus), willow (Salix), poplar (Populus), maple (Acer), hackberry (Celtis), and arborvitae (Thuja)

• All life stages will be found on the bark, especially in twig forks when populations are low.

• Light populations usually cause no plant symptoms but do produce honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
• High populations can cause leaf yellowing and twig dieback. Prolonged infestations can kill plants after a few years.

• There are 2 generations per year in Maryland.
• The crawler emergence periods depend on temperature and can vary slightly from year to year. The approximate times to monitor for them are:
  • First generation – late May to mid-June
  • Second generation – late June to mid-July
• They overwinter on the bark as juveniles.

• No local Growing Degree Days and Plant Phenological Indicator data have been compiled for this species.
• Natural enemies, such as ladybugs and parasitoid wasps, usually provide adequate control without the need for pesticides.

• Mature female covers are oval, dark reddish-brown with a white margin, and up to ⅛” (3mm) long.
• Male covers are elongated, white, and smaller.
• Crawlers are yellow.

• Prefers elm (Ulmus) and may occur more rarely on its relative zelkova (Zelkova); also redbud (Cercis)

• In winter, juveniles and adult females will be found on twigs, especially in branch forks (adults) and in bark cracks (juveniles).
• In summer, juveniles will feed on foliage alongside the veins.

• Trees under stress. Recent transplants or young trees growing in challenging conditions are more prone to damaging infestations of this scale.

• Moderate to heavy infestations will produce large quantities of honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
• Heavy or prolonged infestations can cause premature leaf shedding, stunted growth, and dieback.

• There is 1 generation per year in Maryland.
• The crawler emergence period depends on temperature and can vary slightly from year to year. The approximate time to monitor for them is early May through mid-October.
• They overwinter on the bark as juveniles.

Just before the expected emergence period, start monitoring for crawlers. Since weather trends can shift date ranges, a more reliable prediction of timing can be made using Growing Degree Days and Plant Phenological Indicators. A refined estimate of egg hatch and the beginning of crawler emergence is:

831 degree days

After the peak flowering of Virginia spiderwort (Tradescantia virginiana)

Before the peak flowering of smokebush (Cotinus coggygria)

Natural enemies usually provide adequate control without the need for pesticides.

• Mature female covers are oval, black, and up to 3/16” (4.75mm) long. The cottony white ovisac (egg case) they produce behind their covers are about ¼” (6 mm) in length.
• Crawlers are tan.

Twenty-nine plant families are used by this species.

• Preferences among flowering and shade trees include maple (Acer), elm (Ulmus), hawthorn (Crataegus), dogwood (Cornus), sycamore (Platanus occidentalis), poplar (Populus), and linden (Tilia)
• Preferred vines include grape (Vitis) and its relatives (Parthenocissus)

• In winter, juveniles and adult females will be found on bark.
• In summer, juveniles will feed on foliage alongside the veins.

• Light to moderate populations usually cause no plant symptoms but do produce honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
• Heavy or prolonged infestations can cause premature leaf yellowing, stunted growth, and dieback.
   

• There is 1 generation per year in Maryland.
• The crawler emergence period depends on temperature and can vary slightly from year to year. The approximate time to monitor for them is June.
• They overwinter on the bark as juveniles.

  

Just before the expected emergence period, start monitoring for crawlers. Since weather trends can shift date ranges, a more reliable prediction of timing can be made using Growing Degree Days and Plant Phenological Indicators. A refined estimate of egg hatch and the beginning of crawler emergence is:

872 degree days

• After the peak flowering of Smokebush (Cotinus coggygria)
• Before the first flowering of Japanese Stewartia (Stewartia pseudocamellia)

Fletcher Scale (Parthenolecanium fletcheri)

 This is a native species.

• Mature female covers are hemispherical, yellow-brown, and up to 3/16” (4.75mm) in diameter.
• Crawlers are amber to pinkish-orange. 

• Yew (Taxus), arborvitae (Thuja), juniper (Juniperus), cypress (Cupressus), and hemlock (Tsuga)

• All life stages can be found on twig tips.
• From summer through winter, juveniles can also be found on foliage.

• Light to moderate populations usually cause no plant symptoms but do produce honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
• Heavy or prolonged infestations can cause premature needle yellowing and shedding; small shrubs may die.

• There is 1 generation per year in Maryland.
• The crawler emergence period depends on temperature and can vary slightly from year to year. The approximate time to monitor for them is June.
• They overwinter on twigs and needles as juveniles.

Just before the expected emergence period, start monitoring for crawlers. Since weather trends can shift date ranges, a more reliable prediction of timing can be made using Growing Degree Days and Plant Phenological Indicators. A refined estimate of egg hatch and the beginning of crawler emergence is:

1105 degree days

After the peak flowering of Japanese stewartia (Stewartia pseudocamellia)

Before the first flowering of bottlebrush buckeye (Aesculus parviflora)

• Mature female covers are globular, reddish-brown, and up to ⅛” (3mm) in diameter. They may be lightly dusted in wax, resembling the dried resin that coats spruce buds.
• Male covers are oval, transparent to white, and smaller.
• Crawlers are pinkish or yellow-orange.

• Prefers spruce, especially Norway spruce (Picea abies), black spruce (Picea mariana), red spruce (Picea rubens), and white spruce (Picea glauca, which includes the popular cultivar ‘Conica’, called dwarf Alberta spruce)
• Some pines (Pinus)

•  Near the tips of young growth, especially since mature females look very similar to spruce needle buds. Inspect bud scales (the protective coverings over developing or dormant buds) for scale nestled behind them as camouflage.
• Lower branches are attacked more often than upper branches.

• Light populations may not cause plant symptoms but do produce honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
• High populations can weaken trees, reducing vigor, stunting growth, and making them more vulnerable to infection and winter burn.

• There is 1 generation per year in Maryland.
• The crawler emergence period depends on temperature and can vary slightly from year to year. The approximate time to monitor for them is late June into July.
• They overwinter at the base of foliage as juveniles.

No local Growing Degree Days and Plant Phenological Indicator data have been compiled for this species.

• Mature female covers are hemispherical, dark brown to black with mottling in tan or cream, and up to ¼” (6mm) in diameter.
• Male covers are elongate, flat, translucent, and smaller.
• Crawlers are reddish.

• Prefers pine, especially Scotch pine (Pinus sylvestris), Virginia pine (Pinus virginiana), and Jack pine (Pinus banksiana). Also utilizes Austrian pine (Pinus nigra), mountain pine (Pinus mugo), red pine (Pinus resinosa), eastern white pine (Pinus strobus), loblolly pine (Pinus taeda), shortleaf pine (Pinus echinata), and slash pine (Pinus elliottii)

• All life stages will be found on the twig tips. Look for adult females at the base of needles.
• Abundant ants seeking honeydew are often associated with populations of this scale.

• Light to moderate populations usually cause no plant symptoms but do produce honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
• High populations can cause needle yellowing and branch dieback. Prolonged infestations can kill small plants, especially when combined with environmental stress (such as drought or wind desiccation).

• There is 1 generation per year in Maryland.
• The crawler emergence period depends on temperature and can vary slightly from year to year. The approximate time to monitor for them is June through early July.
• They overwinter on twigs as juveniles.

No local Growing Degree Days and Plant Phenological Indicator data have been compiled for this species.