What Kills Oleander Bushes?

Oleander Caterpillar

• Oleanders have the dubious privilege of having a voracious caterpillar named after the plant. An oleander caterpillar infestation may defoliate an oleander shrub in days. Three generations of caterpillars can attack an oleander in a single year, stripping the leaves and severely weakening the plant. The caterpillars are easily recognizable; they sport long black tufts along a 2-inch-long orange body. While the caterpillars won't usually kill an oleander on their own, they severely stress the plant and leave it vulnerable to drought, disease and other insects. Spray infested oleanders with an appropriate insecticide.

Oleander Leaf Scorch

• Oleander leaf scorch entered North America through an infected plant imported to California, and there is no cure. This bacterial disease clogs the water-carrying tissues of the plant. The edges of the long oleander leaves turn a patchy yellow, then brown as the leaf edges and tips die. The branch tips die back as well, then larger branches. Most plants die within two to three years. Oleander leaf scorch looks like salt burn or even drought damage, but these conditions affect the entire plant, while leaf scorch first affects only a branch or two.

Sphaeropsis Gall

• Sphaeropsis gall is a fungal infection that triggers mutated growth. The oleander may produce bulbous, ugly galls along the branches, or the branches themselves may suddenly shoot straight up rather than following their original growth pattern. Like oleander leaf scorch, there is no cure. Pruning, however, may save the plant. Cut diseased branches 6 inches below the affected area. Examine the cut for dark patches or signs of disease. Sterilize the pruning shears in rubbing alcohol and prune lower, if necessary, until the cut shows no discoloration. Remove and destroy seriously infected oleanders.

Weather

• Oleanders can handle drought, sun, salt and alkaline soil, but a deep drop in temperature kills this shrub. Oleanders are hardy only to 15 degrees Fahrenheit. While low temperatures kill the top growth, well-mulched roots may survive and produce new growth in spring. Prune away winter damage when temperatures stabilize and watch top-killed plants for new growth.