STILL PASSIONATE FOR PASSIONFRUIT?
PART 2 – DO YOU STILL WANT TO GROW THIS FEISTY VINE?
I HOPE readers were able to grab last week’s article which started the sometimes-tortuous journey of growing passionfruit, where we looked at the origins of the passionfruit, choosing a site, soil preparation, planting a young vine and a little about early nutritional requirements of this pretty particular fruit.
Today, the journey continues with some guidance on caring for the vine as it grows and matures, and the challenges of diseases and pests.
Firstly, let’s make sure the vine has enough support.
This climber is described as a “woody” vine, which means that it will need a strong support on which to grow as it gains size and weight.
Strong fencing wire strung at 1m, 1.5m and 2m high, between sturdy posts about 5m apart, is great for the home gardener.
A commercial grower near Bundaberg I visited a few years ago had a similar setup but spaced their vines every 2.5-3m for maximum output from minimum space.
Wire mesh fencing panels are also great, but I’d warn that pruning and removing woody, twisted stems from this type of support is difficult.
Pruning is essential. Passionfruit will flower and fruit on new shoots produced annually.
If the vine is left unpruned, the flowers and fruits are produced further away from the main stem each year, and the centre of the vine becomes a tangled mess.
In our temperate regions, pruning of the lateral growths back to 30cm long should be done in spring, once new growth has started.
(If you live in warmer areas, where no frost occurs, prune in winter.)
Some pruning of new side-shoots can also be done in summer to open up the vine for better disease control and fruit colour.
As for diseases, there are a few to be on the lookout for, as some are usually fatal once contracted by the vine.
Viruses top the most dangerous list. Passionfruit Woodiness Virus (PWV) and Cucumber Mosaic virus can both be easily spread to passionfruit vines, either by seed or cutting propagation from infected plants, or by sap-sucking insects, particularly aphids, and are usually fatal once they take hold.
Both diseases can often infect a vine at the same time, and display similar symptoms, which usually begin on the leaves.
They will develop dark green areas with light yellow spots and can often become crinkled or puckered.
Fruit are deformed, small, and thickskinned at the expense of the centre seed and pulp production.
Colder weather tends to exacerbate the problem.
The major challenge with these virus diseases is that it only takes one viruscarrying aphid to infect a vine, and they cannot be cured.
It’s recommended that vines showing typical virus symptoms be removed and burned.
It has been known for young vines to overcome the symptoms of these diseases if they are in good health.
There are many fungal diseases that also reduce the productivity of, or kill, vines by affecting leaves, stems and fruit.
Three fungal spot diseases which are quite similar in their early symptoms are Alternaria spot, Brown spot and Septoria leaf spot.
All usually start as small, discoloured or brown lesions on leaves, stems and fruit and gradually take on slightly different shapes and colours as each disease progresses. Most cause leaf fall and fruit drop.
All are favoured by warm, moist weather conditions so will usually appear in summer and autumn.
Another fungal nasty to watch for is scab. Small, round, translucent spots form on stems, leaves and fruit, usually in cool, humid weather.
Grey, powdery spores form on leaves and stems and raised scabs form on fruit.
Other fungal diseases that may attack passionfruit include anthracnose, phytophthora blight, fusarium wilt, and sclerotinia rot.
Most, if not all of these fungal diseases are favoured, and spread easily, by extended periods of wet weather.
Unpruned, thick, bushy vines and old age (over three to four years old) also contribute to any fungal disease establishment and spread.
Commercial growers spray preventative fungicides regularly and will remove vines after 3 years and replant.
Home gardeners, on the other hand, try to milk every small, round purple fruit out of their old vines, and it may be advisable to consider planting a new vine every three to four years to maintain production and reduce the probability of disease.
Mulching right along underneath the length of the vine will also reduce the incidence of soil-borne fungal spores infecting vines as it reduces splashing of soil onto lower leaves.
Pests also love passionfruit.
Bugs and hoppers are predominantly sapsuckers, causing mostly superficial damage to vines and fruit, but if in large numbers may cause fruit drop or secondary fungal infections on attack sites.
They include fruit-spotting bugs, passionvine hoppers, Rutherglen bugs, and green vegetable bugs.
Healthy, young vines will withstand minor infestations, but late afternoon sprays with neem or pyrethrum products will help with reducing more damaging numbers.
Other pests (but wait, there’s more) include mealy bugs and scales, also sap suckers, usually found on stems and leaves.
If you find ants on your vine, you’re likely to have sap suckers as well.
In many instances, in a healthy garden, parasitic wasps, ladybird larvae and lacewing larvae do a great job of keeping numbers under control.
If you feel that numbers of these pests are getting out of hand (most vines will tolerate small numbers), you may wish to use an oil spray late in the day, and not in the middle of summer heat.
Mites (oh, will it ever end?) can also do great damage to passionfruit vines
Fruit flies will also try their luck with passionfruit.
They will sting green fruit, with boil-like swellings appearing, causing some very young fruit to shrivel and drop.
However, thicker- skinned varieties closer to maturity may survive, with the eggs either not hatching, or any that do, dying in the hard rind.
Traps and baits are best to reduce fruit fly numbers as exclusion will restrict pollinators reaching the flowers.
Speaking of pollination, boy, are passionfruit extra feisty sometimes.
However, this subject has become bigger than Ben Hur, so stay tuned next week for part three covering pollination, fruit set and varieties.