Scale Insects

Info for the Indoor Gardener

Among the hard-to-find garden pests are the scale insects, both soft and armored. The information below the Google ads helps the Indoor Gardener emerge triumphant in this battle.

DESCRIPTION

• soft scale insects are most common on houseplants
• adults motionless
• flat, oval to spherical shapes
• 1/8 - 1/2 inch
• tan, black, brown in most species
• excretions form hard shells
• secrete honeydew similar to mealy bugs
• armored scales
• 1/16 - 1/8 inch
• round
• central spot on bodies
• no honeydew
• piercing mouth parts

LOCATION

• plant stems
• underside of leaf
• sometimes on top of leaves
• some species prefer leaf veins
• soft scale: twigs and leaves

MULTIPLICATION

• prefer warm, dry environments
• also prefer over-fertilized houseplants
• slower life cycle (see below) than many other garden pests that infest houseplants

DESTRUCTION

• suck juices from the plant
• weaken plants
• honeydew and mold interfere with photosynthesis
• leaves yellow or spot, wither, drop off
• branches die

DETECTION

• hard to notice
• ants often give them away when attracted to honeydew secretions
• hard scales: produce spotting around location
• these garden pests look like small lumps on leaves or stems
• search for leaf problems or branch die-back
• check for honeydew and sooty mold that grows from it
• search in crevices of bark on stems, leaf joints, under leaves
• use 10x magnifying lens

SOLUTION

• easy if found early
• isolate the plant immediately
• cut off affected branches
• can wipe, rub, or pick off the scale insects if not too profuse
• use soapy water (warm) to wash plant, rub off each leaf, rinse
• insecticidal soap doesn't work well on adults; minimally on young, as it's repelled by waxy coating of scale insects
• suffocate them with insecticidal oil, such as Neem oil
• use cotton swabs with rubbing alcohol (apply weekly, at least 2-3 times)
• Malathion as spray or dip (follow directions)
• Soft Scales:
• spray oils
• rubbing alcohol or soap sprays (especially in crawler stage)
• if using insecticides for crawler stages, continue usage up to 4 months
• if using pyrethrin or resmethrin (follow directions), apply weekly
• systemic insecticide, such as imidacloprid, usually works for soft scale insects
• increase light
• avoid over-fertilization
• increase root strength and health
• natural predators for greenhouses, conservatories, and large indoor spaces:
• ladybugs
• green lacewings
• parasitoids (predatory wasp)
• Armored Scales: horticultural oils are most often recommended
• Chemicals: follow directions carefully; time for crawler stage when most effective
• use sticky yellow cards to detect crawler stage

• Soft Scales: Coccidae
• Coccus herperidum = most common brown scale
• Saissetia coffeae = hemispherical scale
• Armored Scales: Diaspididae
• Florida alone has 13 Families of scale insects (including mealy bugs)
• Florida also has over 175 species of armored scales
• Florida has more than 60 species of soft scale insects
• Life Cycle:
• female produces eggs continuously for several weeks
• eggs hatch under the mother
• eggs hatch in 1-3 weeks
• nymphs or crawlers - move short distances to establish their own feeding area
• produce shell and emit honeydew in new location
• 2 - 4 months until adult; rarely move
• some species grow wings and move to other plants

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