Question
Hello, I have had two wonderfully full INDOOR WINDOW BOXES overflowing with Impatiens. But recently I noticed small crystalline globules on stems and leaf joints (not on leaves themselves).  When crushed, the globules feel like sugar.  I took a cutting and put it in a plastic zip-lock bag to take to the nursery for diagnosis.  When I arrived an hour later, the crystalline globules appeared to have melted.  And there was a slight stickiness in the bag and on the cutting, almost as if the crystals had melted.  Is this an insect or is it a case of the plant over-producing a sort of sweet sap?  I have a very strong feeling that I over watered them but now the soil is dry.  How can I bring the plants back to full health (they are looking weak/a bit wilty) and still have that sticky/crystalline globule stuff on their stems.  Is there any chance of keeping them over the winter indoors?  Or must they pass away?  They are also just starting to get leggy (though I've been assiduously pinching them with great results).  Any advice would be appreciated!
Jonathan in Manhattan


Answer
I have a feeling you're not going to like this.

This 'honeydew' you observe, this sticky, clear substance that seems to crystallize when it dries, is an Aphid secretion rich in Sugar.  It's usually the first symptom you notice when attack is imminent.  Sort of like thunder before a downpour.

Aphids are very common soft-bodied plant pests.  An Aphid's mouth resembles a hypodermic needle, which it uses to pierce stems and leaves.  New World Encyclopedia says Aphids have 'modified mouthparts (mandibles and maxillae), called stylets, adapted to suck Phloem sap from vascular plants.'  The sap oozes out of the Phloem vessels and into their mouth parts.  Here's the entry:

www.newworldencyclopedia.org/entry/Aphids

Points out New World, 'As the plant keeps this sap under high pressure, once a Phloem vessel is punctured, it is forced into the Aphid's food canal.'  Aphids also 'drink' the water in Xylem vessels on plant stems to get more liquid.

Sap tends to be extremely high in Carbohydrates -- way more than any insect needs.  Aphids deal with this by secreting the excess carbs as droplets of 'honeydew' -- the sticky excreta sweetened with trehalulose and melezitose which you noticed on your Impatiens leaves.  This sharing of bodily fluids makes Aphids more than the sum of their parts.  They transmit Viruses as they wine and dine; their honeydew triggers growth of Fungi and Mold on plant leaves, nourished by the high concentration of nutrients.  Whiteflies, Mealybugs and Ants fall all over themselves to get this honeydew.  Ant colonies will actually ADOPT Aphids as pets, and 'milk' the Aphids to stimulate more.

You have got to get rid of those Aphids.

Easiest: Wash daily under water.  OK, maybe this is not so easy.

Easier: Empty a spray bottle of detergent, then fill with water and gently mix in a few teaspoons of liquid dishwashing soap.  Spray without mercy.  Do this outside.  Let spray dry.

LIG Favorite Plan of Action: Purchase a bag of Ladybugs; refrigerate a few hours; take Impatiens outside and, in the dark, sprinkle chilled Ladybugs at the plant base.  In the morning, they will begin to feast on all the Aphids you do not see.  By week's end, Aphids are history.  Rate me, please.

THE LONG ISLAND GARDENER