Roses

Rose Care: White fly

white fly damage to leaves

Severe white fly damage to rose leaves.

When: White fly infestations can occur from summer to autumn, but they are uncommon to settle on roses.

Where: country wide

Remedy: Apply Koinor as a drench. Watch this video on how to apply Koinor. Spray with Plant Care. The rape oil contained in Ludwig’s Insect Spray which is the main ingredient of our main Cocktail should smother the white fly. It is a very soft insecticide to use.

Frequency: Weekly spraying over two weeks should put an end to them. One application of Koinor will also do the trick.

Effect on plant: The effect of a White Fly infestation is reduced growth through a considerable loss of sap and nutrients sucked from the phloem as well as the lack of photosynthesis once a black fungus settles on the honeydew that is secreted out of the white fly and dripped onto the leaves below

Info: Whiteflies are small Hemipterans that typically feed on the undersides of plant leaves..

Alternative combat: Washing the underside of the leaves with a sunlight liquid emulsion. Lady birds as beneficial insects that prey on the white fly.

If no action is taken: Reduced growth through a considerable loss of sap and nutrients sucked from the phloem as well as the lack of photosynthesis once a black fungus settles on the honeydew that is secreted out of the white fly and dripped onto the leaves below.

 

White Fly and Soot on leaves

It is not often that white fly make an appearance on roses. If it does happen, the first obvious sign that White Flies have found the rose as a suitable host and feeder plant is a black fungus growing on the leaves.

The White Fly (Trialeurodes vaporariorum and Bemisisa tabaci) does not belong to the family of flies (Dipteres or two wing flies) but has four wings and the development stages are quite different to that of most other insects. That is why they cannot be controlled or eradicated with the usual insecticides.

There are 1200 known types of White Flies that are mostly active in warm and tropical regions. They can fly and jump. The adult white fly is about 1.5 mm large and is covered with a white powdery wax-like layer over the whole body, except the eyes. The wax is produced by four wax glands under the body and is quickly spread out with its legs.

The development goes through six stages: egg – four larvae and nymph stages – one pupae stage to adult stage.

Fertilised eggs produce males while unfertilised eggs produce females. The female sucks on the underside of the leaves during the egg laying period. She produces eggs with ‘studs’, which are embedded in the leaf and are kept fresh by absorbing moisture through the stud. The first stage larvae moves  around the leaf until it finds an open suction point and there it stays throughout its development into the pupae stage. This is not a completely dormant (pupa) period, because the pupae still suck sap until just before hatching into an adult White Fly. The total cycle takes about 22 days in our summer.

The effect of a White Fly infestation is reduced growth through a considerable loss of sap and nutrients sucked from the phloem as well as the lack of photosynthesis once a black fungus settles on the honeydew that is secreted out of the white fly and dripped onto the leaves below (the secretion of honeydew by a heavy population of White Fly in 1 hectare of cotton is about 300 kg.). White Fly is also a known virus carrier.

Insecticides with the active ingredients of imidacloprid and piriproksifen are effective to combat the white fly. Neem Oil, Rape Oil (Ludwig’s Insect spray) and White Fly Insecticide (piriproksifen) are available to gardeners.