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Credits: Biovision-Infonet

A number of virus diseases have been reported, notably the passion fruit woodiness potyvirus. Affected leaves show light and dark green mosaic pattern often with light yellow speckle.

Sometimes small, yellow ring spots may develop on upper leaf surface. Infected fruits are small and misshapen with very hard rind and small pulp cavity.

When affected fruit is cut, the inside rind tissue may have brown spots. Some strains of the virus cause cracking of affected fruits.

They are spread by aphids (Aphis gossypii and Myzus persicae) grafting and pruning knives.

The virus has a wide host range including bananas, cucurbits and many weeds.

What to do:

• Use virus-free planting material.
• Disinfect pruning tools with household bleach.
• Use resistant hybrids, or rootstocks of yellow passion fruit.
• Remove diseased vines from the field.
• Do proper weeding.
• Avoid planting bananas and cucurbits near passion fruit fields.

(Phytophthora nicotianae var. parastica)

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Affected leaves are water-soaked and light-brown in colour. They fall readily, leading to defoliation of the vines. Affected areas of the stem are first purple and later brown above the graft union.

They may completely girdle the stem causing wilting and collapse of the vine. Fruit symptoms comprise of large, water-soaked areas.

Diseased fruits fall readily and in wet weather become covered with white, fungal growth.

Another strain of the fungus (Phytophthora cinnamoni) causes root rot. Yellow and purple varieties have different patterns of susceptibility. The yellow vine is susceptible to P. cinnamoni, and the purple vine is more susceptible to P. nicotianae.

Both fungus strains attack both passion fruits and can cause root rot, wilt, damping off and leaf blight. Fungal spores are initially produced in wet soil beneath the vines and are splashed up to lower leaf canopy.

The disease is favoured by wet, windy weather.

What to do:

• Good field sanitation.
• Pruning and keeping a grass sward under the vines to minimise spore splashed up to the lower leaves.
• Graft to resistant rootstocks (e.g.) P. caerula.
• The application of copper-based fungicides every 2-3 months during the wet season reduces disease incidence in areas where the disease is likely to be serious. Stem lesions may be painted with a copper fungicide.

(Fusarium oxysporum f.sp. passiflorae)

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Fusarium wilt (also called collar rot) symptoms consist of yellowing of leaves, the collar region of affected plant at soil level turns brownish and vertically cracks and vines wilt followed by a complete collapse of the plant.

On dissection of infected stem, vascular tissues show brown discolouration.

What to do:

• Affected parts should be removed and burned. Snap off the affected parts or remove the affected plant manually.
• Do not cut tissue and then use the knife on healthy plants.
• Keep the base of the plant clear of grass and weeds, which favour fungal growth.
• Grafting to wilt-resistant yellow passion fruit rootstocks (e.g. P. caerula) is the most practical way of control.

(Septoria passiflorae)

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The disease attacks leaves, stems and fruits. Brown spots up to 2 mm with minute, black dots (fruiting bodies containing fungal spores) develop on leaf surface.

Infected leaves fall readily leading to defoliation of vines. Similar spots may form on the stems albeit elongated.

On fruits light-brown spots studded with minute black dots may be formed. The spots often join up to cover large areas of the fruit. Affected fruits ripen unevenly.

Spores produced by black dots (fruiting bodies) are blown to adjacent vines during wet, windy weather thus further spreading the disease.

The disease is spread by rain, dew and overhead irrigation. Warm moist weather favours disease development.

What to do:

• Disease management measures for brown spot disease (see above) are equally applicable for Septoria spot.

(Alternaria passiflorae)

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The most important disease worldwide is brown spot on leaves, vines and fruits.

Symptoms are brown spots, up to 10 mm diameter, on the leaves, often extending along the veins and drying out in the centre.

On the stems, spots are up to 30 mm long, and when they occur at the leaf axils may kill the vine, resulting in dieback.

On the fruit, the spots are light brown, round and sunken; they often merge, covering large areas, and produce red-brown spore masses.

Spores, produced on the leaf, stem and fruit, are dispersed by wind-blown rain. Warm, moist weather favours disease development. (EcoPort)

What to do:

• Yellow passion fruit and its hybrids are more tolerant to this disease.
• Field sanitation (collection and disposal of fallen diseased fruits, leaves and vines).
• Pruning vines to reduce density and thereby reducing humidity within the crop. It also facilitate better air circulation, light and spray penetration and cover.
• Timely sprays with copper based fungicides. During humid weather, when the vines are growing rapidly, reduce the intervals between spray applications to 2 or 3 weeks to ensure that new growth is adequately protected.

Credits: Biovision -Infonet

Biological methods of plant protection. The most important disease on passion fruit is brown spot (Alternaria passiflorae) on leaves, vines and fruits.

Phytophthora blight (Phytophthora nicotianae) causes the wilting of shoot tips and crown rot, particularly where water stagnates occasionally.

Septoria spot, caused by the fungus Septoria passiflorae, causes extensive spotting of leaf and fruit, and occasionally of the stem. Yellow passion fruit and its hybrids are more tolerant to these diseases.

Fusarium wilt (also called collar rot) is caused by the soil-borne fungus Fusarium oxysporum f.sp. passiflorae; the shoots wilt, followed by a complete collapse of the plant. Grafting to wilt-resistant yellow passion fruit rootstocks is the most practical way of control.

Damping-off caused by Rhizoctonia solani and Pythium spp. can be a problem in nurseries and soils should be sterilised.

A number of virus diseases have been reported, notably passion fruit woodiness potyvirus (PWV). They are spread by aphids (Aphis gossypii and Myzus persicae) and pruning knives.

Other virus diseases are ringspot from Cote d’Ivoire, which is similar to PWV.

The most practical control is to use clean planting material, clean pruning tools and resistant hybrids, or rootstocks of yellow passion fruit.