Nasturtium Pests

Aphids

• Small and soft-bodied, aphids do considerable damage to nasturtiums when large groups attack plants at once. Curling, yellowed leaves, stem damage and destruction of new shoots occur as the aphids suck out the vital plant liquids. During the summer, aphids can grow from newborns to adults in eight days, and each adult produces up to 80 new aphids at a time, rapidly increasing the population. Keep the area clear of weeds and debris where aphids live and avoid excessive nitrogen fertilizer, which attracts aphids. Insecticidal soap removes aphids from plants. Many beneficial insects such as wasps and ladybugs will feast on aphids, keeping the plants clear.

Caterpillars

• Caterpillars chew through flowers and foliage, leaving holes throughout the plant. They completely consume buds and new shoots; excessive feeding severely damages and, on occasion, kills the plant. Handpicking caterpillars removes the pests, and keeping the area clear of weeds where caterpillars gather will reduce the population on the plants. Beetles, spiders and green lacewings are all natural predators and feed on caterpillars.

Leafhoppers

• Short and slender, bright or dark, leafhoppers damage nasturtiums by removing plant fluids, causing leaves to turn pale or brown and new shoots to die off. Some leafhopper species secrete honeydew that then promotes the development of sooty mold on plants and causes foliage to darken and fall from the plant. They are highly active and difficult to completely remove from plants; the best defense in reducing the leafhopper population is insecticidal soap.

Spider Mites

• Oval shaped with eight legs and appearing as tiny, moving dots, spider mites cause leaf damage by sucking out the foliage cell contents. High infestations can significantly damage leaves, causing stippling, discoloration and premature leaf drop on plants. Avoid overwatering plants, because water stress will increase the spider mite population. Insecticide treatments for other pests may cause mite outbreaks; therefore, stick to insecticidal soaps or a blast from the garden hose to remove any mites that move in.

Whitefiles

• Living in groups on the underside of leaves, whiteflies are sap-sucking insects that leave honeydew on foliage, causing yellowing and loss of leaves. With yellow bodies and white wings, whitefly populations grow rapidly when the weather warms up and they lay their eggs; whiteflies feed on the leaves throughout each stage of development. Hard to remove once established, whiteflies are not susceptible to insecticidal controls. Remove and discard infected leaves, keep the area clean of debris, or use a reflective mulch to deter whiteflies. Insecticidal soap will reduce, but not remove whiteflies from the garden.