“My
string-of-pearls plant feels sticky and has patches of what looks like white
fuzz on it. What’s wrong?”
Looking
through several books, including David V. Alford’s Pests of Ornamental Trees, Shrubs, and Flowers, The Organic Gardener’s Handbook of Natural Insect and Disease Control, and Insect Disease and Weed I.D. guide, we diagnosed the
plant with mealybugs. Female mealybugs are covered with a fluffy white wax, and
they lay their eggs in similarly fuzzy-looking white wax sacs. (The male
insects have wings and are small and difficult to see.) Mealybugs eat sap and
secrete something called honeydew, which gives the plant a sticky feel. (Ants
also like to eat the honeydew, so a mealybug infestation may give way to an ant
infestation.) According to Pippa Greenwood’s Pests and Diseases, succulents (like the string-of-pearls) are some of the most common mealybug hosts.
Our
gardening books provided a wealth of ideas for combating the infestation. Debra
Lee Baldwin’s Succulents Simplified suggests moving the plant away from any
others to somewhere with good air circulation and spraying it down with a mix
of isopropyl alcohol and water until all the bugs are gone. Introduce ladybugs,
parasitic wasps, or mealybug destroyers, if possible, as they’re all some of
the mealybug’s natural predators. Commercial pesticides are also available. If
a spray doesn’t seem to be penetrating the mealybugs’ protective waxy coating,
try using a small paintbrush to dab it directly on them. The Plantfinder’s Guide to Cacti and Other Succulents by Keith Grantham and Paul Klassen and
Cacti and Succulents by Hans Hecht both suggest painting the mealybugs with
denatured alcohol or an alcohol/dish soap mixture to remove the waxy coat. Leaf
shine spray is also effective against mealybugs, but it will also remove the
pleasant powdery bloom on any plant with glaucous leaves.