Passiflora are prone to a number of viruses.
They includeChrysanthemum B carlavirus, Passiflora latent carlavirus, Passifloraringspotpotyvirus, Passionfruit
woodiness potyvirus, & Purple granadilla mosaic virus. Some are introduced by biting insects such as greenfly but others, especially in hybrids
propagated by cuttings are in the genes.
Their symptoms include leaf distortions, loss of vigour,
poor flowering and poor fruiting. Some viruses can weaken the plant enough to
Nutritional deficiencies can look very similar to viral infections and of course are linked
in that a plant with a poor nutritional status will be more liable to succumb
to viral attack. Note that leaf distortions can be caused by the act of biting alone which disrupts leaf growth.
Frost injury may also cause leaf distortions in some plants.
Damage is often most notable at the
beginning and end of the growing season. There is anecdotal evidence that when
growing quickly the plants can leave the virus further back in the stem and so
cuttings can be taken at the height of the growing season to start a new plant
without the virus.
For the amateur gardener my best advice is to
feed almost all Passiflora well with slow-release fertilizer throughout the growing season. I
say almost because some like P. incarnata does not seem to
respond well as it usually grow in very poor soil.
Tissue culture of apical meristems often with heat therapy is widely used
to to remove viruses from commercially important plants. Of course even if a
virus free plant is achieved unless it can be grown in very controlled
conditions all it needs is one biting insect for a virus to be re-introduced.
Plants do have their own immune system and if virus damage is particularly
bad I will feed the plant intensively with fertilizer which seems to help
suppress the viruses. The comparison shots of of the same P. x belotii before and after treatment above show how effective this can be. The
treatment was watering the plant pot regularly with a high potassium NPK
fertilizer with trace elements. Rose fertilizers often have very good profile.