Cut Flower Updates: September 19, 2025

Oleander aphids are an occasional pest of some cut flower crops. You may be more familiar seeing these bright orange aphids feeding in dense clusters on milkweed plants in gardens and natural settings (hence their common name, "milkweed aphid"), but their host range comprises the family Apocynaceae, which includes the popular cut flower crop tweedia.

Oleander aphids are viviparous, meaning that rather than depositing eggs, they deposit nymphs (live young), and all of their young are clones of the adult female mother. (Fun fact: male Oleander aphids don't even exist in the wild!) Because of this unique reproductive strategy, their populations can build very quickly, leading to rapid infestation of host plants.

Like all aphids, oleander aphids are soft-bodied insects with piercing-sucking mouthparts that they use to feed on the sugary phloem sap of their hosts. Feeding can cause deformation and stunted growth. The aphids also secrete sticky honeydew, which often leads to sooty mold. Between the dense presence of the insects themselves, their feeding damage, and their sticky secretions, these aphids can quickly render a floral crop unsellable.

In outdoor settings, natural predators like parasitoid wasps, lacewings, and syrphid flies can keep aphids in check, but control in greenhouses can be a challenge. Plants and plugs coming into the greenhouse should be inspected for aphids prior to planting. Growers can use biological control agents to introduce predators into their greenhouse systems. Larvae of predatory midges, Aphidoletes aphidimyza, can be purchased commercially and are some of the best aphid eaters available. They are most effective during the summer months, as they become inactive during cooler temperatures and shorter day lengths. Entomopathogenic fungi like Beauveria bassiana, also commercially available, can be effective if employed while aphid populations are still low. It usually requires repeat applications.

Want to learn more about greenhouse and landscape biocontrol? Check out Penn State Extension's Biocontrol School, which is being held on October 15^th in Manheim.