Cotton Whitefly, Tobacco Whitefly, Tabakwitvlieg (Afr.)
Glasshouse Whitefly is a small white insect. It belongs to the order containing true bugs however appears more like a micro moth or fly. Whitefly is an important agricultural pest that has been a common problem for many commercial crops over the last decade. They are sap-suckers, sucking up plant tissue through two finely adapted stylets. Their feeding behaviour is invasive and has the potential to transmit diseases between plants. As well, copious amounts of honeydew, a byproduct of whitefly feeding, is excreted over the foliage. This can attract mould to the area, which can also result in some form of secondary infection.
Whitefly is an agricultural pest which can transmit disease from their feeding.
They can feed on a wide variety of indoor-grown plants making severe infestations more likely.
Adults are tiny, growing only 1.5mm, with four white wings. They are pearly white and often fly up 'in clouds' when disturbed on the host plant. Nymphs are oval and flattened, translucent with a green tinge. A powdery white wax usually is evident when a nymph has settled to feed. Later nymphal stages appear more like scale insects, immobile and latch to the plant. The final nymphal stage takes the form of a flattened disk, with a fine waxy fringe spanning the body. Eggs are pear-shaped, yellowish, and very small. They are also inserted within the leaves tissue, so cannot be seen with the naked eye.
Whitefly is fairly conspicuous, so infestations should be easily spotted. The nymphs are sap feeders. During feeding, they produce honeydew on which sooty mould grows and builds-up. Together with aphids, whiteflies commonly transmit viral diseases to plants. Diseases can lead to stunted growth, malformed and curling leaves. This is seen especially in young plants.
Whitefly infestations tend to be more problematic indoors, for example, in a glasshouse setting. In most cases, whitefly is spread to glasshouses via new plants. Check or quarantine plants for any nymphs prior to putting it in the greenhouse. Planting rhubarb in greenhouses is thought to deter whitefly too. Whitefly lay their eggs underneath the leaves of plants, so these areas should be inspected regularly. Any spacing between plants should be kept clear of weeds and debris. The use of netting can sometimes improve protection. For lighter infestations, plants can be gently hosed down to remove whitefly and eggs. Ant traps placed near affected plants will aid controlling any secondary infestations. Whitefly is drawn to the colour yellow. You can use yellow cards or sticky traps to attract whitefly and monitor the infestation level. Insecticidal soaps and neem oil can give some control over whitefly, and it's less harmful to the environment when compared with pesticides. Bottle labels should be read carefully. Oils can react badly with high temperatures and burn the surfaces of plants. Beneficial garden creatures such as beetles, wasps, lacewings and spiders will eat whiteflies. These can be attracted into the garden using a few simple tricks, such as incorporating insect hotels or by letting parts of the garden grow a little wild.
There are pesticides available for home gardeners. Please be warned; whiteflies are capable of developing tolerances to the toxins found in sprays. Systemic insecticides can sometimes eliminate whitefly, be sure to get good coverage beneath the leaves (where the younger whitefly hide). Please read bottle instructions carefully, taking care not to spray any plants that are in flower. Such pesticides can be extremely toxic to wildlife, so should be applied with extreme caution. Likewise, if you are planning to eat your harvest, make sure the food plant is listed on the bottle label and follow instructions.