Passionfruit cultivation

Growing Considerations

Are you considering growing passionfruit? Is it because you would like an endless supply of passionfruit as a dessert topping, or the possible financial return? Here are some key factors that you should consider...

Objectives

• a hobby. 
• a lifestyle - an income but little or no investment return. 
• as an investment.

It has been said that one person can look after 400 plants on a full-time basis. You must have the time to put into the crop i.e. spraying (fortnightly) during the growing season - from January to July depending on your locality, trailing the vines, harvesting the fruit from the ground before they get burnt from the summer sun, cleaning & grading the fruit for sale whether it be for export or the local market. Passionfruit require attention every day during the growing season, not just at weekends.

Key Success Features

The following Key Success Factors must be met for passionfruit growing to be viable:

• the proposed site should ideally be north facing and frost free. 
• passionfruit should be planted in rows running North to South 
• free draining soil - passionfruit do not like "wet feet". 
• adequate shelter established before planting to protect from wind damage. 
• a soil test will determine the nutrients required for ideal growing conditions. 
• adequate rainfall or access to irrigation during the growing period and dry spells. 
• effective plant and machinery for spraying, mowing and other orchard activities. 
• a suitable hygienic area available to clean, grade and pack the fruit. 
• the greatest returns are received from exporting passionfruit. There are many New Zealand and overseas requirements relating to exporting Sub Tropical fruit which growers must comply with. Grower registration, Spray certification etc.

Passionfruit vines require a warm moist environment to thrive. Commercial passionfruit production is only possible in relatively frost free locations. However the vines will tolerate a slight frost of minus 1-2 degrees C for short periods. More severe frosts will kill the growing shoots, cause severe fruit damage and fruit drop.
Your orchard should ideally be established in a deep, well drained sandy loam. Poorly drained soils cause the vines to become susceptible to root disease which can rapidly kill the plants. Where natural drainage is inadequate a suitable drainage system should be installed before planting.

Indicative Set up costs

These can vary depending on the structure used to grow the vines. The following costings (May 2002) relate to the "A" frame structure with the apex being approximately one metre apart from the uprights.
To hold all the above timber in place you will require six 100mm and twelve 75mm (decking nails) galvanised nails for each frame. Eight staples per frame are required to support the wire on the frames.
To anchor the wire at either end of the row you require two deadman (two 1.8m posts) or two screw in galvanised 1.5m anchor.
A coil of 2.5mm galvanised wire coil (to train the vines up between frames - eight wires on each frame for the vines and one just above the posts to carry an irrigation pipe) is required. An average coil of wire is 650 metres in length.
You also have to consider whether you will employ a contractor to ram the posts or dig the postholes yourself. Do you require the services of a fencing contractor, paid per hour, to tension the wires or do you have the necessary skill and fencing equipment to do the job yourself?
Passionfruit Plants propagated by a nursery are sold per plant. You can grow them from seed if you have a plastic house, the time, and allow for the cost of potting mix.

Passionfruit Growing Requirements

Purple passionfruit require a warm, sheltered, frost-free site for a commercial planting to thrive and be profitable. The soil must be free draining as passionfruit are very susceptible to "wet feet" and will succumb to any water-logging of the soil.
Passionfruit will only tolerate light frosts (-1 to -2 degrees C) and heavier frosts can severely damage an orchard. Cold winds can also put passionfruit under severe stress and if winds persist, can introduce an early attack of woodiness virus. The only counter remedy for this virus is total removal of the vine.
Passionfruit vines will grow an a wide range of soils, but good drainage and aeration are essential. A deep drained, friable sandy loam is best. Heavy clay soils are unsuitable. Where natuaral drainage is inadequate a suitable drainage system should be installed before planting. Seek local advice before laying a drainage system.
Planting of a suitable shelterbelt is recommended in all passionfruit growing areas of New Zealand. These should be trimmed every 1-2 years depending on the species selected. Root pruning of the shelterbelt is very important as the roots will quickly invade the orchard and rob the soil of nutrients. This causes the vines to go yellow and the fruit to be small.
Root pruning should be done to a depth of 1m every second year. A root saw is the most effective way of pruning as it stops any rejoining of the roots.

Passionfruit Growing Structures

Being rampant climbers, passionfruit need substantial structures to support the heavy crop loading. The three main trellis structures used by New Zealand's commercial growers are "A" frames, pergola and fence. Many growers have adapted and modified these structures to suit their individual needs.

"A" Frames

As the name suggests, these are fabricated in the shape of an "A" and usually made from timber, but steel can also be used. They need to be strong to support the heavy loading of foliage and fruit.
If using timber, 100mm x 50mm is recommended. The "A" frames are attached to posts 150mm (minimum) in diameter and 1 metre long with 500mm above ground. Row spacings vary, depending on the machinery being used but about 3.5m is recommended.
The short posts are driven into the ground about 6m apart in the row and the "A" frames are attached to these. At each end of the rows, about 2m from the last frame, a 'deadman' is driven to attach the wires (a deadman is a substantial post at least 1.8m long with a small end diameter (SED) of 150mm, driven with 500mm above ground). A galvanised screw anchor can also be used.
Four 12-guage wires are strung each side of the frames and the framework of the vines will be trained to these. The top wire is usually about 2m high for ease of vine handling and each subsequent wire is about 500mm apart. It is important to tie back each end frame to prevent it from collapsing inwards

Advantages

• Fruit only needs picking up once a day
• Reduces the cost of mowing and weeding
• Gives 50 percent more canopy area
• Gives better protection from sunburn
• Fruit gets good spray coverage
• Gives better wind protection

Disadvantages

• More costly to erect both in labour and materials
• Foliage can get very dense in between the A frames
• More training/pruning required to keep gap at top open for sunlight penetration

"Y" Frames

As the name suggests, these are fabricated in the shape of an "A" and usually made from timber, but steel can also be used.Constructed similar to "A" frames, refer above.
The frames are braced between each upright arm which leaves a totally open area between the rows.
This aids the movement of warm air and sunlight and enables spraying to be done by overhead boom to spray downwards to achieve better penetration. Frame bracing can be attached to taller upright row posts, if required.

Pergola

A pergola system consists of 2.4m posts being driven to 2m above ground in rows 4m-5m apart. The posts are 6m apart down these rows. Laminated 100mm x 25mm timber is attached across the rows to the top of the posts and steel can also be used.
A deadman is driven at the end of each row to attach the wires (see A frames) and a screw anchor can also be used. A 12-guage wire is run along the tops of the posts, attached with a staple and fastened off each end to the deadman.
Wires are spaced about 500mm apart across the block and each end pergola has to be tied back to the deadman to stop it collapsing inwards. Some variations of this system are used by some growers to increase cropping area.

Advantages

• Gives good protection from both sunburn and wind
• Fruit needs to be picked up only once a day
• Fruit gets good spray coverage
• Mowing and weeding costs reduced
• Disused kiwifruit structures can be used

Disadvantages

• More costly to erect
• A strict pruning regime required to keep gap at top open for sunlight penetration

Fence

Originally, most commercial passionfruit were grown on the fence system but now this has largely been superseded by the other two systems. A fence is a row of 2.4m posts driven to 2m above ground. Posts are 6m apart down the row and at the end of each row is a deadman or screw anchor (see A frames) for the attachment of wires.
Rows can be 2m - 3m apart depending on the machinery being used. A 12-guage wire is attached at the top of the post and two more wires are run about 700mm apart down the post. There are many variations to this fence system.

Advantages

• Cheaper to erect
• Winter pruning may be quicker

Disadvantages

• Fruit is more exposed to climatic adversities such as wind and hail
• Harder to get good spray coverage on the fruit
• More mowing and weed control required
• Sunburn on fallen fruit more of a problem, fruit needs to be continually collected on sunny days.
• Fruit quality generally inferior to other systems

Diseases

A number of serious diseases can reduce yields and kill passionfruit vines if not controlled.

Grease Spot

This is caused by the bacterium Pseudomonas passiflorae and is one of the most serious diseases of passionfruit in New Zealand. It infects leaves, stems and fruit, leading to severe crop losses and even death of vines.

Symptoms

On leaves, it causes irregular olive-green to brown lesions, often surrounded by a light-yellow halo. If unchecked severe defoliation can result. On the stems of young growth the first signs of infection are small slightly sunken, dark-green, water-soaked spots. These develop into light-brown, markedly depressed areas.
On older wood, symptoms range from small, slightly sunken, smooth, dark-green circular spots, to large, dark-brown, cracked lesions, which may completely girdle shoots and kill vines. Early signs of infection on the fruit are small, dark-green, oily spots. These develop into roughly circular, greasy, or water-soaked patches. Premature fruit drop and fruit decay result. Grease spot is said to be most active in autumn and winter, between March and August. However, a condition known as hard grease spot, also caused by Pseudomonas passiflorae, has become prevalent on passionfruit and is active in summer. The symptoms are similar to ordinary grease spot except that the fruit infections dry out and cause a hard brown patch on the skin, instead of leading to decay. This results in a downgrading of fruit and loss of income.

Bacterial Blast

Blast is caused by a bacterium, Pseudomnas syringae, which is a relative of the grease spot pathogen.

Symptoms and Control

The symptoms of the two diseases are similar, and control measures are the same. Where good control of grease spot is obtained, blast should not be a problem.

Brown Spot

This is a serious fungous disease, caused by Alternaria passiflorae, which affects leaves, stems and fruit. It occurs mainly in spring and early summer.

Symptoms

On leaves, small brown spots appear first. These enlarge, develop a lighter-coloured central area, and become irregular or angular in shape.
On stems, elongated dark-brown lesions appear, usually near leaf axils or where stems have rubbed against the supporting wire. Infection spreads from these points and whenever the stem becomes completely girdled the shoot suddently wilts and fruits collapse.
On fruit, spots first appear as pinpricks, which enlarge into sunken circular lesions with brownish centres. Eventually the rind round the diseased area becomes wrinkled and the fruits shrivel and drop.

Septoria Blotch

Caused by the fungus Septoria passiflorae, this disease attacks leaves, stems and fruit. Even a light infection results in defoliation and premature fall and loss of fruit. The disease is more common during summer and autumn.

Symptoms

On leaves, tiny superficial, irregular, light-brown spots appear, quickly followed by severe defoliation as infection spreads.
On stems, spots similar to those on leaves appear. They become deeply sunken but remain minute.
On fruit, the infection initially appears as small spots, similar to those on the leaves and stems. The spots develop into extensive superficial leasions causing premature drop and fruit decay.

Bitter Rot

The fungus Glomerella cingulata causes this disease and can be responsible for significant fruit loss, especially in hot, humid conditions in the summer months. Infection is facilitated by any damage to the skin of the fruit.

Symptoms

Dark, soft lesions rapidly develop on infected fruit that can colonise whole fruit. Infected fruit will fall to the ground.

Control

The routine protective fungicide programme based on copper sprays will afford protection but under stringent infection conditions may need to be repeated at short intervals in the height of summer.
Picking up and removing infected fruit is a good hygienic practice.

Sclerotinia

Sclerotinia sclerotiorum is the causal pathogen of this disease.

Symptoms

It can affect stems where lesions can enlarge to cause a girdling and collapse of the shoots above the lesion. The hard dark sclerotes which are a means of carrying the fungus over from one season to the next can often be seen in infected shoots.
It can also infect fruit with infections rapidly becoming pale brown lesions that can develop over a whole fruit. With advanced infections a mass of fluffy white fungal growth is produced in which the black sclerotes can be seen. Infected fruit falls to the ground, and the sclerotes will carry the infection potential over to future seasons.
Infection occurs mainly in the November-December period when vines are wet for 16-24 hours and temperatures are in the 15-200C range.

Control

Where Sclerotinia has been a problem application of a suitable fungicide after pruning when the main structure of the plant can be covered is worthwhile.
Orchard hygiene is also important. Infected fruit should be picked up and removed from the orchard, and infected shoots cut out below the lesion and destroyed. This will ensure that the sclerotes are removed and minimise the carryover of infection within the orchard.

Crown Canker

This is a lethal condition of passionfruit, causing sudden wilting, leaf and fruit drop and death. It has been a major factor in limiting the commercial production of passionfruit in New Zealand.
A number of Fusarium species have been isolated from plants suffering from crown canker, the most prevalent of which is Fusarium redolens. Other fungi known to be involved include Fusariumavenaceum, Gibberella baccata, and Gibberella saubinetii.

Symptoms

The condition usually occurs close to ground level, centred on wounds caused by frost, growth cracks, mechanical damage, fertilizer or herbicide burn, or by pest injury such as that caused by slugs or snails. Infections often progress to girdle the stem at or near ground level.

Control

Unfortunately there is no known control for crown canker, so all efforts to reduce the risk of infection are worthwhile. These would include selection of the best sites to minimise frost and weather damage, regular frost protection with bracken fern or similar material each winter, and avoiding injury to the base of the plant by implements, fertilizer or herbicides.
It is also good practice to keep the base of the plant clear of grass and weeds, which favour fungal growth and harbour slugs and snails. Where collars are placed around stems to protect against herbicide damage, slug pellets placed inside the collar will help control these pests.
Plants suffering from crown canker should be carefully removed and destroyed by burning.

Phytophthora Root Rot

Phytophthora is known to affect passionfruit. In New Zealand two species are mainly involved, Phytophthora cinnamomi is prevalent in summer and autumn, and Phytophthora megasperma is prevalent in the spring.Both fungi can cause the death of vines, but it is thought that the stress and damage they often cause open the way for invasion by Fusarium and death of the plant from crown canker.

Control

Improving drainage is one way to reduce the risk of Phytophthora infection.

Thielaviopsis Root Rot

This is another fungous disease which can affect passionfruit growing on heavy soils. It is caused by Thielaviopsis basicola.

Symptoms

Intected plants are unthrifty, with poor-coloured foliage. The roots show signs of decay and are often blackened.

Control

With mild infections sometimes a severe pruning to balance the top growth with the loss of roots can keep the plants going, but severely infected plants should be removed and replaced.

Woodiness

Woodiness may be caused by the cucumber mosaic virus, the passionfruit woodiness virus (a member of the potato virus Y group) or alfalfa mosaic virus, or a combination of these or possibly other viruses as well.

Symptoms

On leaves it causes yellow spots, flecks or mottling, and there is crinkling or distortion. It also shows as shortened internodes on the stems, bunching of foliage and stunted growth. Symptoms are most apparent during late autumn, winter and early spring.
On fruit it causes thick, hard, distorted woody rinds, often with characteristic scabs and cracks. Pulp yields are much reduced.

Control

Plant only virus-free plants and remove and replace severely infected vines. The disease is transmitted by aphids and possibly also by pruning tools. Once vines become infected there is no known control. Obviously infected plants should be rogued out and destroyed. Virus symptoms are minimised by promoting vigorous vine growth and where necessary aphids should be rigorously controlled.
In older blocks or where some vines may be infected, disinfecting pruning tools between vines or parts of a block could be worthwhile. This can be achieved by dipping pruning tools in a 1% solution of hypochlorite (bleach) for a few seconds, neutralise by a dip in vinegar and protect tools with a spray of CRC or Valvoline.