|I just planted oleander and now my neighbors tell me that they breed caterpillars. Is that fact or fiction? I love their beauty and aroma but do not want to be beset by these pests.|
The adult moth (Syntomeida epilais jucundissma) is striking in appearance. The bluish to purplish moth has white dots on its black wings. The moths resemble wasps as they actively fly in and around oleander shrubs. It's the orange caterpillars with black spots and black hairs that cause problems for some gardeners.
Caterpillars are the larval stage of butterflies and moths. In order to enjoy watching butterflies and moths feeding on the nectar of flowers, some of the caterpillars must survive to become the adult butterflies and moths. Butterfly gardening is currently a popular landscaping trend. Many gardeners intentionally plant certain plants to attract butterflies. If you plant oleander shrubs, chances are very good that you will eventually attract oleander moths.
The mated females will then lay clusters of 25 to 75 orange eggs on the undersides of the oleander leaves. After hatching, the caterpillars begin feeding on the leaves. They first skeletonize and later completely devour the leaves.
The full grown caterpillars enclose themselves in silk cocoons, later emerging as the adult moths. The adults live about five days. The entire life cycle takes about 60 days. They can have three generations per year.
Oleander caterpillars only feed on oleander plants, which are native to areas of Europe and Asia.
(This relationship between pest and plant is sometimes referred to as the key plant, key pest concept. It's very common. Other examples include crape myrtles and crape myrtle aphids, azaleas and azalea caterpillars, camellias and tea scale, roses and black spot, pecans and pecan scab, squash and squash vine borers.)
Even though oleander caterpillars can temporarily damage the appearance of oleanders, they cause no long-term damage for the oleander plant--the damage is aesthetic. Oleander caterpillars can consume great numbers of leaves; however, if the plant is otherwise healthy, new leaves will be produced and the plant will continue to grow. Long term, there will be no evidence the plant ever had a problem.
So to spray or not to spray for oleander caterpillars has to do with a person's tolerance level.
If you can't tolerate the temporary aesthetic damage caused by oleander caterpillars, you can spray with Bacillus thuringiensis (Dipel), which targets caterpillars. (Remember that B.t. will harm any type of caterpillar, even those of desirable butterflies.) When using any pesticide, always follow the label directions and precautions.
For more information on oleander caterpillars, you can contact Larry Williams, Extension Agent I, Horticulture
Okaloosa Extension Service, University of Florida, (850) 689-5727