On every stem, on every leaf,... and at the root of everything that grew, was a professional specialist in the shape of grub, caterpillar, aphis, or other expert, whose business it was to devour that particular part. ~ Oliver Wendell Holmes

Crop Pests - Whitefly

Whitefly Whiteflies are common greenhouse pests. Both immatures and adults feed by extracting fluids from plant cells. This results in excretion of honeydew and the growth of sooty mold. All stages are typically found on leaf undersides but only the adults and the newly hatched larvae are mobile.

Infestation can accelerate rapidly and is easily detected by the swarms of flies that rise from plants that are disturbed. Adult whitefly are capable of laying up to 200 eggs in groups on the underside of the leaves. Tiny larvae emerge which search out suitable feeding sites on the underside of the leaves where they settle down and lose the ability to move. This immobile "scale" stage is pale green, about 2mm long and lives on the underside of the lower leaves only. The life cycle consists of adult laying eggs, to larvae, to scale and finally to adult, this whole process can be completed in as little as 3 weeks in the summer.

Whitefly adults and immatures feed on sap. As they feed, they excrete honeydew, a sticky substance that causes unsightly glistening and supports the growth of black sooty mold. Very large populations of whiteflies cause stunting of plant growth, and leaves may die. Whiteflies can also transmit virus diseases. Once whiteflies are controlled, new plant growth is normal. Usually populations are not high enough to stunt ornamentals, and damage is mostly caused by honeydew, sooty mold, and nuisance populations of flying adults.

Encarsia Formosa

Protect your plants by introducing a natural parasite of whitefly called Encarsia Formosa. They are most effective if they are introduced early in the season AS SOON as the first whitefly appear and the temperatures are above 10°C / 50°F.

Encarsia are introduced to the greenhouse as parasitised whitefly scale on small white cards which are hung on the lower leaves of the plants. It takes about 7-14 days for the Encarsia to emerge from the parasitised scale and start to hunt whitefly. If the conditions are not suitable or if the infestation is very heavy use sticky glue traps to cut down the adult numbers first and then introduce Encarsia.

They'll come to a Sticky End!

If you can't catch 'em then trap 'em - Glue Traps!

Hang yellow glue traps next to plants in spring to control early whitefly infestation. Sticky glue traps should be placed adjacent to the growing point of the plants or placed in plant pots. For plants such as tomatoes, the traps should be hung in such a way as they can be raised as the plant grows.

Glue Trap

The traps will catch the Whitefly which will fly around the tops of the plants. Whitefly are attracted by the bright colour of the traps and become stuck to the trap. They should be changed as they become dirty.

Whitefly Damage

Damage from Whitefly

Worth a Read!

The Garden Pests and Diseases Specialist

The Garden Pests and Diseases Specialist book cover

All gardeners know the disappointment of discovering that their bedding plants have been nibbled, their prized fruits and vegetables riddled with rust.

This is the essential guide to identifying the likely culprits and banishing them from the garden. The book starts with the basics, introducing common pests and diseases and looking at the best ways of dealing with them.

Take a look at The Garden Pests and Diseases Specialist