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Detecting the presence of whiteflies
Whiteflies are winged insects belonging to the superfamily Aleyrodoidea. They are no more than three millimeters long. They are classified as piercing-sucking insects because they pierce plant tissues and feed on their sap.
Among the best-known species are:
- the tobacco whitefly (Bemisia tabaci);
- the greenhouse whitefly (Trialeurodes vaporariorum);
- the citrus whitefly (Dialeurodes citri);
- the black olive whitefly (Aleurolobus olivinus).
To reproduce, whiteflies lay eggs on the undersides of leaves. Their flat, white larvae resemble mealybugs.
Contributing factors
High temperatures provide a favorable climate for the development of larvae. This is why whiteflies are found on greenhouse and indoor plants.
But whiteflies are also rampant in the garden and vegetable patch. They attack ornamental plants such as hibiscus, begonias, coleus, hydrangeas, Plectranthus scutellarioides, vegetables (cabbages, tomatoes, eggplants, potatoes, lettuce) and fruit.
How it works
Whiteflies suck sap from plants. As they feed, they secrete a toxic substance that penetrates the leaf blades and spreads throughout the plant. Even flowers and fruit can be affected.
The larvae secrete honeydew, a viscous, sweet substance. It promotes the appearance of fumagine, a fungus, on the leaves.
Infested plants are weakened and become more susceptible to virus transmission.
Symptoms
Several signs indicate whitefly contamination:
- leaves become sticky ;
- foliage is covered with black rot caused by fumaginia ;
- yellow or whitish spots appear on leaves;
- plant growth is slowed.
Treatment
Whiteflies fear cold and humidity. To keep them away, aerate and mist your plants regularly. Outside flowering periods, you can apply a systemic whitefly insecticide.
Another way of keeping whiteflies at bay is to prepare a mixture of water and black soap and spray it on the foliage. You can also buy sticky traps to hang in greenhouses or indoors. If you prefer to use biological pest control, call on our insect allies. Encarsia formosa, a species of wasp, is a natural predator of whiteflies.
Finally, whiteflies, like aphids, are attracted to nasturtiums. You can plant a square of them away from your crops to concentrate whiteflies.
If one of your plants shows signs of invasion, don't panic. Fog its foliage with a decoction made from tobacco, nettle purin and tansy. You can also shower the plant with lukewarm water to get rid of insects and larvae.
