Control Measures: Cultural Methods Spraying for Oleander Caterpillars

Oleander caterpillars feeding on Oleander shrubs can cause damage that ranges from minor to extreme. Areas where the damage is severe include Florida, coastal regions of Alabama and southern Georgia.
This pest of Oleanders can actually be found in any locale where the Oleander plant flourishes but has not been seen as a pest in California.
In most areas where this caterpillar has been found, its damage has been noted as slight to moderate but in other areas (especially Florida and coastal region of Alabama) the damage can be quite severe.

In light to moderate caterpillar infestations, damage to leaves of the Oleander shrub is seen as small holes chewed between leaf veins, progressing to complete skeletonized leaves. In severe cases this caterpillar can strip the Oleander shrub of its leaves and small stems in a short time period. However, this shrub is very sturdy and many customers tell us that their shrubs rebounded after being ravaged by the offending worm.
Damage to the shrub is explained in the life cycle of the Oleander Caterpillar. Severity of damage to your shrubs and frequency of oleander caterpillar infestations will determine which methods of control to take.

Description, Life Cycle of Oleander Caterpillar, Wasp Moth

Oleander caterpillars are the immature stage of a moth called the Polka Dot moth. The Wasp moth gets its name from its appearance which does resemble that of wasps more than moths. This is a beautiful moth that has blue/green coloration on its wings. The wings and body both have contrasting white dots, hence the common name of "polka-dot moth."
The young caterpillars hatch from eggs laid by the adult Wasp moth. The first meal of this caterpillar is its egg shell.
After its emergence from the egg, the tiny Oleander caterpillar begins feeding on its host plant. It is protected from the toxins of the Oleander by its feeding habits. In its first instars this pest feeds only on the leaves, avoiding the highly toxic stem and leaf veins. Oleander toxins are highly concentrated in the plant's vascular system. As noted by Daniel E. Mullins, Extension Agent for Santa Rosa County, Florida, the damage to the Oleander corresponds with the specific caterpillar instar (stage).
The smallest will begin to feed on the underside of the Oleander leaves. As they grow and transform to larger instars these caterpillars readily consume all of the leaves except for the veins, leaving a characteristic skeletonized appearance. As the caterpillar gets larger, it is capable of cutting through the actual leaf stem which cuts off the flow of toxic sap.
The feeding habits of different larval stages are what allow the caterpillar to survive feeding on a plant that most pests must avoid.
The pupal stage is the final one before the adult moth emerges to complete the cycle. These pupae are often found on groups or pupal clusters. There have been numerous reports of these clusters creating quite a mess under the eaves of homes or buildings that are near or adjacent to the Oleander plants.

Control Measures: Cultural Control Methods Spraying for Oleander Caterpillars

Deciding on which control method or methods to take will depend on several factors, including severity of the problem, any history of severe problems with Oleander caterpillars in your garden, controlling pests in a butterfly garden and other situations. Spraying for caterpillars (using botanical sprays or an insecticide spray) is a last resort for many gardeners. We have seen many instances of severe infestations in the Gulf Coast region where pesticide use is a must, if one desires to keep Oleander shrubs in their landscaping plans.

Cultural Methods

At first sign of caterpillar infestation, hand picking the caterpillars from the shrub is your best bet. Drop the Oleander caterpillars into a bucket (or other container) that contains a strong soap solution. The soapy water should kill the caterpillars that cannot escape the container.
As the situation deteriorates you will begin to see more damage to the leaves and the damage will probably be noticed in higher levels of foliage.
As the sheer number of caterpillars increases, clip off stems and leaves that are infested. Remember that the sap of the Oleander is toxic and any vegetation that is pruned should be disposed of in a safe manner. Place pruned vegetation in a plastic garbage bag or leaf bag and dispose the bag properly. Do not allow horses or other grazing animals to feed on this vegetation! You should also wash your hands thoroughly after handling the plant's parts.

When caterpillars are feeding on very tall shrubs, selective pruning may no longer be a sensible option. It is at this point that you must decide whether to replace the Oleanders with another ornamental plant or spray the caterpillars with an effective spray.

Spraying for Oleander Caterpillars

After all mechanical means of control have been exhausted you may have to use a spray to kill the Oleander caterpillars. There are two basic spray types to consider: botanical and synthetic pyrethroids.
BT (Bacillus thuringiensis) is a material that kills caterpillars and is often used in vegetable or flower gardens. The plus side of using a BT spray is that it only effects caterpillars and will not harm desirable butterflies or helpful insects such as lady bugs. If BT is used, the predators of the Oleander caterpillar (fireants, predatory stink bugs) are not harmed. This is a good product to use if you have Oleander shrubs in a butterfly garden. Continuous spraying will probably be necessary in order to kill the different generations of caterpillars that are usually present at any given time.

Many people (including lawn care professionals) in the coastal areas of Florida and Alabama have turned to synthetic chemicals to eliminate Oleander caterpillars from their tall Oleander shrubs.
Over the past few years there have been some surprises in which chemicals are effective against this pest. It was originally thought (with good reason) that systemic products such as Acephate (also called Orthene) should easily eliminate any caterpillar that is feeding on ornamental plants. The Oleander caterpillar rarely responded to Acephate. This caused many turf and ornamental specialists to turn to Talstar for a good spray. When used against a wide variety of household, turf, tree and ornamental pests Talstar has given a great level of control for long periods of time - while using a very small amount of active ingredients to get the job done.
When heavily infested shrubs were sprayed with a solution of Talstar, the caterpillars were knocked down but only to return the next day.
Through much trial and error, professional strength Permethrin products proved to be the best for controlling or eliminating Oleander caterpillars. Permethrin professional grade products (Dragnet) are used the Oleander caterpillars are killed. In heavy or stubborn infestations, two or three applications might be necessary.
These applications should be made at about 10 to 14 day intervals to effectively kill the different generations of Oleander caterpillars that are probably present.
Use a hose-end sprayer to apply Permethrin to large or tall stands of Oleander shrubs. One to two ounces of Permethrin concentrate per gallon of water will yield a solution that will kill Oleander caterpillars.

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