Japanese beetles, aphids and the larvae of flower borer flies and sunflower moths eat purple coneflowers. The Japanese beetle feeds on the foliage of the coneflower, leaving a lacy pattern of veins behind. Aphids suck away nutrients from the plant by draining the sap from the stems and leaves. The larvae of flower borer flies and sunflower moths eat the florets and pollen of the plant.Continue Reading
Japanese beetles can be controlled by the weekly application of an insecticide. To eradicate the beetles completely, the larvae that live in the ground must be killed. One method for doing this involves the application of milky spore disease bacteria to the affected area. It may take as many as three years to rid the ground of all larvae. Adult beetles can also be lured away from the coneflower by pheromone traps.
If aphids are the issue, adding ladybugs, a natural predator of aphids, to the environment in the early summer is helpful. Spraying insecticidal soap on aphids dissolves the protective wax coating their bodies. This leads to dehydration and death. Plants receiving a soapy water application need to be rinsed with clean water after two hours.
The best way to prevent infestation by the larvae of sunflower moths and flower borer flies is to make sure there is air circulation around the plants. Disposing of dead leaves and other debris discourages these insects from creating a home in the area.Learn more about Outdoor Plants & Flowers