PGI Landscape and Gardening
Contributed by Ellen Brown, Master Gardener,
elenphil@comcast.net
September, 2010
Spanworms, IO caterpillars and oleander caterpillars arrived mid-June. If you have snow bush, oleanders, citrus, palms or hibiscus then you have probably encountered them. If you don’t have these plants but a neighbor does, then you will encounter at least the adult moths of the spanworm and oleander caterpillar. All caterpillars have voracious appetites, and they will strip a plant in no time. Total defoliation will not kill the plant, but if it occurs repeatedly year after year, the plant may be more susceptible to other pests.
The spanworm, a type of inchworm, feasts on snow bush. This inch-long greenish-yellow and black caterpillar is the larva of the day-flying white-tipped black moth. The outer fringe of the forewings is white. This tiny moth has an erratic and fast flight pattern usually at eye-level altitude. For more information go to http://charlotte.ifas.ufl.edu, click on “fact sheets”, “horticulture”, then scroll down to “The Snowbush and the Spanworm.”
The oleander caterpillar is particularly fond of oleanders, hence its name. The adult stage of the oleander caterpillar is often called the polka-dot wasp moth. Resembling a wasp, the body and wings are a beautiful iridescent blue/green. Small white dots are found on the body, wings, legs and antennae. The tip of the abdomen is red/orange. Also a day-flying moth, it has a slow flight pattern. The adult female lays eggs in a cluster. The early instar caterpillars feed gregariously grouping together in clumps as a strategy for protection from predators. For detailed information, go to http://edis.ifas.ufl.edu/in135.
Locally the IO caterpillar is often seen feasting on palm fronds, as well as citrus and hibiscus leaves. This caterpillar has at least three discrete color forms. The usual last instar form is light green with a distinct lateral body strip of red and white. The body is covered with tiny clusters of stinging spines which release a poison when contact is made. You are not likely to see the adult IO moth as it is active at night. This is too bad as it, like many moths, is truly beautiful. The hindwings, when displayed, have distinct dark “eyes” with a dark outer circle, hence the name “IO.” Like the oleander, eggs are laid in clusters and the early instars feed gregariously. Gardeners are more likely to back into an IO caterpillar when working around plant material, than to have a face-to-face encounter. If stung remove any spines with adhesive tape, apply ice compacts, mentholated Vaseline, or use an antihistamine. Learn more about the IO by going to http://edis.ifas.ufl.edu/in203.
Management of these caterpillars includes spraying with a bacterial spray such as Bacillus thuringiensis or “BT”, an insecticidal soap or spinosad as per the label directions. Before using any pesticide read the label. Hand picking the spanworm and the oleander caterpillar, then dropping them in a jar containing isopropyl alcohol is an alternative to spraying.
Make a habit of visiting your yard daily this time of year to monitor all plants for pests and diseases. Vary the time of day you visit. This will give you a “heads up” on early detection and intervention.