1. Brown spot (Alternaria passiflorae)
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.
Management:
2. Septoria spot (Septoria passiflorae)
The disease attacks leaves, stems and fruits. 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.
Management:
Disease management measures for brown spot disease (see above) are equally applicable for septoria spot.
|
3. Fusarium wilt (Fusarium oxysporum f.sp. passiflorae) |
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.
Management:
4. Phytophthora blight (Phytophthora nicotianae var. parastica)
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 (Phytophthora cinnamoni) causes root rot. Yellow and purple vines 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.
Management:
5. Passion fruit woodiness potyvirus (PWV)
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, Myzus persicae) and pruning knives. The virus has a wide host range including bananas, cucurbits and many weeds.
Management:
1.6. Aphids (Aphis gossypii and Myzus persicae)
Aphids damage plants by sucking plant sap causing curling, wrinkling or cupping of infested leaves, giving deforming plants. They spread viruses and excrete honeydew, which coat the plants and leads to growth of sooty mould, which can diminish the photosynthetic capacity of plants.
Management:
7. Thrips damage on passionfruit
Thrips (Thysanoptera sp.) cause stunting of young plant. They feed on leaves, flowers, and fruits. Attacked plant parts shrivel. Attacked flowers and young fruits fall prematurely. Feeding by thrips on fruits causes tiny lesions, which affect the marketability of the fruit, especially in fruits for export.
Management:
RWA
ENG