Houseplant insect
infestation: a few tips from a pro
Marianne Willburn
(2/2019) To continue a bit where I left off
last month with general houseplant care, I’d
like to go into more detail about dealing with
the insect infestations that tend to show up
in the dead of winter, and which, if not
caught quickly, can weaken and kill the plant
you have taken months to look after.
By February, most houseplants have endured
months of suboptimal conditions, not to
mention suboptimal care, and insect levels may
be higher than we think. We’ve still got at
least three months before these pots can
safely hit Mid-Atlantic patios and decks for
the summer season, and if we want to have
anything to show off, it’s time to do
something.
Scale, aphids, spider mite, fungus gnats,
whitefly, mealy bug…these are not bullies that
simply go away when the gardener turns the
other cheek. If we don’t cope with them now,
they will only get worse.
Even if you were exceptionally careful in
the autumn, you may still have an insect
issue. Check your plants. Every October I
bring in plants that have been treated at
least twice with horticultural oil over a two
week period outside, yet something always gets
by. Pregnant aphids treat my succulents like a
home for fallen girls – also sneaking in as
eggs that are too tiny for these poor eyes.
Sticky honeydewed foliage is usually my
first sign – or at least the sign I can no
longer cross the room to ignore without
gummed-up feet. Honeydew doesn’t just coat
foliage, it coats floors, furniture,
lampshades and anything else that happens to
be underneath the little vampires. It is the
excrement of sucking insects – a sugar-rich
liquid expelled just as quickly as the sap is
ingested. A bit like a newborn baby without
the diapers.
It goes without saying that by the time you
notice it, you’ve got a big problem on your
hands – and it’s going to take more time and
effort to solve it than it would have taken to
keep an eye on the plants in the first place.
But now is not a time for judgement (says
she, conveniently). It is a time for action.
So I consulted local plant guru and yoga
instructor, Jan Faulkner, whose successful
business, Tropical Plant Outfitters beautifies
skyscrapers and office buildings throughout
the DC Metro area.
Jan is a pro at keeping plants looking
lovely – and many is the evening that she has
sat on my couch, innocently and beautifully
sipping a beer before suddenly and violently
pulling off three offending stems from a
neighboring houseplant. She always apologizes
profusely, assures me they "had to go" and
then seamlessly goes back to talk of yoga and
calming the mind. The contrast is a priceless
one and makes me smile to think of it.
I trust her completely – after all, her
business relies on great looking plants – so
when I found that a gifted agave was covered
in scale and my large and small umbrella
plants (Schefflera spp.) were similarly
affected this year, I decided to stop limping
along with a cloth and mayonnaise and find out
what the professionals were using.
Jan happened to come over during a warm
spell, which made things much easier as we
dragged these seven and ten gallon pots onto
the deck to treat them. Had it been a cold
day, they would have been dragged to a central
place on my tile floor where spray would not
hit furniture or curtains.
Jan’s weapon of choice is OMRI listed Safer
Insect Killing Soap and she mixed up a bottle
as we sat on the deck, enjoying the
unseasonable warmth. Though she has used neem
oil, she hates the smell (as do I), and her
method of spraying the plant, then gently
working through the foliage with her hands to
remove the insects is made vastly more
pleasurable by working with soap over oil.
She inspected the plants, pronounced
judgement, ("it’s not that bad"), and gave the
first one a light haircut to remove awkward
stems, dead foliage and invisible crawlers
(the first instar stage of scale insects) that
like to congregate at the tips of new foliage.
And then the spraying and fondling began.
Leaves, stems and woody crotches were all
addressed in turn. ‘A clean crotch is really
important.’ she stressed, and I could not
disagree. Within a few minutes we’d caressed
that first schefflera to within an inch of its
life, and our hands, whilst covered with soap
and scale, were not so covered as to make me
turn in my gardener’s license in shame.
As it was later in the season and the
infestation had been moderate, Jan applied a
light granular systemic for houseplants from
Bonide and bid me to fertilize and repeat the
soap procedure in a few days. For light
infestations, she skips the systemic and does
fine with two rounds of soap.
The spiny variegated agave didn’t need
fondling; or rather, if it did, it wasn’t
getting any from me. I sprayed where I could
(scale loves those crotches), and applied
systemic to the soil, watering it in well.
A week later and the worst is behind us.
The schefflera are happy, glossy and clean as
a whistle, and the agave is much improved as
well – though another treatment will be
necessary. Insecticidal soap will also kill
spider mite, aphids, mealy bugs and a host of
other bad boys. For those in the insect air
force - fungus gnats, white fly, and winged
aphids, try yellow sticky cards. Jan
recommends them, and after nosing about a bit
into the underwear of Longwood’s 300ft indoor
green wall, I can report that so do
horticulturists in the know.
With houseplants trending higher and higher
these days (macramé
is so back, btw), it pays to stay ready to
fight the pests that can quickly turn a thing
of beauty into a spindly, scraggly bit of
shame. Use the methods that make the most
sense to you, but use something before there’s
no going back.
Read past editions of The Small Town Gardener
Marianne is a Master Gardener and the author of Big Dreams, Small Garden.
You can read more at www.smalltowngardener.com