Disease and pest management
In our farms we have had good and bad experiences when farming passion fruits. We have compiled some of the harmful pest and diseases that have led to big losses in our farms that we would like you to avoid and also have the knowledge on how to control them.
1. Mealy bugs:
These are small, oval, sucking insects with a cottony white waxy covering to their bodies. Infestation generally occurs on the tender floral buds and fruits. Adults and nymphs pierce the attack parts and suck the sap. The insect secrets a sugary substance over which a black coating develops. Such development interferes the food manufacture by the leaves and it downgrades the quality of the fruit.
2. The Passion Vine Mite
The passion mite may cause serious damage to the vines. Unless damage from these mites is checked the vines may die or the growth may be so adversely affected that there is a marked reduction in fruit. To the naked eye this mite appears as scattered, reddish patches on the lower surface of the leaves along the mid-rib and veins as well as on the fruit surface. The mites attack the young leaves and suck the sap, the affected leaves are generally curled. As a result a heavy infestation may cause complete defoliation and the plant may eventually die.
3. Fruit flies
These insect pests puncture the immature fruits while the rids are still tender. As the fruit enlarges a woody area develops around the puncture. If the fruit is still quite small and under developed, the damage may be sufficient to cause it to shrivel and fall from the vine. If the fruit is well developed, it may grow to maturity. At the time of opening, the area around the puncture has the appearance of a small woody crater which disfigures the outer appearance of the fruit but apparently does not impair the quality of the juice.
Aphids infest passion fruit and plants and suck the sap. On fully grown vines, severe damages seldom results. On seedlings, however, aphids may cause severe damage. Aphids are known to be efficient vectors of passion fruit woodiness virus, which is proving to be a serious disease of passion fruit in Kenya.
Routine Pest Control Measures
The control of pests, which attack the passion fruit, involves two basic problems,
(1) The destruction of insects which attack the plants.
(2) The preservation of the insects whose function in pollination is of vital importance to fruit plant.
The problem is complicated because both beneficial and destructive insects are so closely associated with the plant. The injurious insects must therefore be eliminated without destroying the beneficial ones. An approach to this problem is the proper timing of spray applications. Less damage to the beneficial insects, when a farmer schedules his chemical spray application during periods when the pollinating insects are not active.
We advice farmers on varius control measures to use when controlling pest in their farms.
PASSION FRUIT DISEASES
(1) Brown spot disease – Alternaria passiflorae
The disease is caused by fungus known as Alternaria pasiflorae; this is characterized by the development of brown spots and lesions on the leaves, stems and fruits.
The attacked stem normally turns brown and this leads to ring barking. As a result the functions of the plant tissues, which are responsible for carrying food from the leaves to the roots and vice versa, are interfered with and there is subsequent dieback. As the infection progress, the spots enlarge forming a series of concentric rings and the infected leaves and fruits may fall prematurely. The vines may wither from the affected parts upwards particularly after the stem has become desiccated. The quality may also shrink and drop from the vine. When the attacks are very severe, fruits begin rotting either from the stalk or from the bottom producing a brown color in the attacked parts.
The disease may infect vines of all ages. Humid conditions, accompanied by slightly higher temperatures than normal may accelerate the spread of the disease.
Control of Brown Spot Disease
(a) Field hygiene
This involves the constant removal of all infected material, which should be burnt at least once a week. The pruning frequency should also be increased during humid periods when the disease appears to spread very rapidly.
(b) Chemical control
Besides keeping the cines reasonably exposed to the sun by judicious pruning, regular spraying is very necessary to reduce losses where the disease is prevalent.
(2) Woodiness disease
Virus causes the disease. The infection is characterized by grossly misshapen fruits, which show abnormal thickening and hardening of the tissues of the fruit wall and a reduced pulp cavity. The foliage becomes mottled with dark green areas localized on the raised portions of the leaves. The leaf color between dark green and the raised areas is yellow green (mosaic appearance). The leaves are frequently misshapen and reduced in size. In some instances there is lack of growth of the terminal shoot accompanied by a bunchiness of the harsch-textured terminal leaves. The disease is one of the most serious diseases of passion fruit and may curtail the commercial life of a vineyard. Aphids spread the virus, by at the transfer of sap from diseased to healthy plants during pruning and other cultural operations.
Fungal sprays cannot control woodiness, it is therefore recommended that plants showing typical symptoms of the disease be uprooted and burnt. Also ensure you get seedlings that are certified to avoid this disease. Plant hygiene measures should be practiced, especially during training and pruning. Pruning knives should be sterilized by use of appropriate disinfectant, both before and after use. Passion fruits should never be planted again in the same field or in the immediate vicinity particularly where a severe attack has occurred.
3. Fusariam Wilt
Fusariam wilt is serious disease in Passion fruit particularly the local purple passion fruit. The disease is soil borne, which means that the fungus lives in the soil from where it attacks the rooting system of the affected plant. The disease spreads upwards along the stem and one can easily recognize brown patches scattered on the stem. The brown patches can easily be mistaken for the brown spot disease and can only be diagnosed by an experienced person. Since the attack originates from the roots the transaction of water and minerals from the soil are interfered with, the plant starts to wither and eventually it dies.
There is no control of this disease once it attacks the plant. A farmer should uproot and burn it and never again to plant that passion fruit which is very susceptible to this disease on the same soil. We use the Yellow passion fruit which is resistant to this disease, which is used as a rootstock against this disease.