Oleanders Under Attack by Caterpillars

Better check your Oleander shrubs weekly throughout the summer. Early outbreaks of the Oleander caterpillar are resulting in stripped foliage and weakening of these popular ornamental plants.

The Oleander caterpillar (Syntomeida epilais jucundissima) is a striking insect in both the adult and larval stage. The adult, or moth is about one inch in length. It is bluish or purplish in color, with white dots on its black wings. Mated females lay clusters of 25 to 75 orange eggs on the undersides of Oleander leaves. Adults live for about 9 days and the life cycle requires about 60 days for completion.

The larvae hatch and first feed on their own eggshells. After that, they begin feeding on the leaves. They first skeletonize the leaves and as they grow, begin to devour entire leaves. The caterpillars are orange, with black dots and black hairs that protrude from their bodies.

Oleander is known to be a very poisonous plant and this is the only species that the Oleander caterpillar feeds upon. So the question often arises, how does this insect thrive on a plant that contains toxins?

The larva has developed a defense against the alkaloids that exude from wound sites. Since the poison is found in the vascular system, the newly hatched larvae feed strictly upon leaf tissue and not veins. When they reach a certain size, they bite through the leaf veins near the base, which stops the flow of the toxic sap. They can then safely consume all parts of the leaf above the wound.

Like most caterpillars, these are easier to control when they are small. Weekly inspection of Oleander shrubs would allow for early detection and control. Recommended insecticides include Sevin, Orthene and B.t. The biological product, known generically as B.t. is sold under several trade names including Dipel, Biotrol and Thuricide. Follow label directions carefully when using these and other pest control products.

Adult stage: note white spots on black wings.

Larval stage of the Oleander Caterpillar

Question of the week: The fruit began shriveling and falling from my fig trees about a month ago, although the trees appear healthy. What could be causing this?

Answer: Fig trees are sensitive to a fluctuation in soil moisture when the fruit is developing. The demand for water increases greatly during this time and if the soil is allowed to dry out even once the tree will often sacrifice, or drop its fruit in order to maintain its health.

Use deep mulches of leaves, pine needles or bark underneath trees. This will help to prevent moisture loss due to evaporation from the soil surface. Water slowly and deeply twice each week, if sufficient rainfall does not occur while fig trees are fruiting.