Basil (Ocimum basilicum) is a common herb in Italian, Thai and other types of cooking. It grows relatively easily during warm weather in Sunset's Climate Zones 1 through 45, although it does occasionally suffer from pest problems. Whiteflies and aphids both feed on basil plants. These insects damage the plant leaves, reducing the amount of basil available for the gardener to harvest. Luckily, it is possible to physically remove these insects with water or to reduce their populations through biological controls.
Look for aphids and whiteflies on basil leaves, making sure to check the underside of the leaves. Aphids are usually small, green and wingless. Whiteflies are small, yellowish bugs with white wings. Some symptoms of aphid damage include yellowing leaves, curled leaves, stunted shoots and distorted leaves. Symptoms of whiteflies include yellowing leaves and leaves that dry up and fall off. Both insects can also cause black sooty mold to appear on basil leaves. Monitor basil plants and catch aphid infestations early, before the leaves start to curl and provide hiding places for the aphids.
Remove severely infested leaves to help reduce pest populations on the plants.
Spray the aphids and whiteflies with a hose to wash them away. Alternatively, consider vacuuming whiteflies off of basil leaves with a small battery-operated vacuum.
Introduce predatory insects to the garden. Parasitic wasps, ladybugs, lacewings and syrphid flies all reduce aphid populations. Lacewings, big-eyed bugs, minute pirate bugs, Scymnus species, Chilocorus species and the Asian multicolored lady beetle reduce whitefly populations.
Continue examining the basil plants on a regular basis, and wash off any aphids or whiteflies.
Things You Will Need
- Water sprayer
- Predator insects, such as parasitic wasps, lady bugs and lacewings
- Small battery-operated hand vacuum
- Reflective aluminum foil or plastic mulch
- An insecticidal soap or neem oil can help get rid of aphids, but insecticides also have the drawback of getting rid of natural aphid and whitefly predators. Insecticides are not normally recommended for whitefly infestations.
- For persistent whitefly infestations, consider using a reflective mulch to help deter the insects.
- University of California Agriculture and Natural Resources: Aphids Management Guidelines
- University of California Agriculture and Natural Resources: Whiteflies Management Guidelines
- National Gardening Association: Growing Basil
- Clemson University Cooperative Extension: Basil
- Sunset Plant Finder: Ocimum Basilicum
- PhotoObjects.net/PhotoObjects.net/Getty Images