How to treat grape diseases
A grape is a non-climacteric fruit, which looks like a berry. It grows from the deciduous woody vines. They can be eaten raw or processed to make oil, vinegar, wine, jelly, juice or even jam. However, grapes like many other fruits get certain diseases. The common grape diseases are downy, powdery mildew and Botrytis bunch rot. A great amount of money is invested in the control of these grape diseases. The grape diseases however do not occur all the time. As the vines get older, other disease start cropping up. This may be due to weather conditions or even management. Some of the most common grape vine pests are deer’s, birds and insects. Some people therefore think that pesticides could help curb grape disease but then it is not recommended.
This is done when the shoots are 10-20 cm long. It reduces the incidence of the shoots being infected and inflorescent being lost. The fungicides should also be used before and after the vines have produced flowers. Also, the fungicide should be sprayed 1-2 weeks before the harvests. If the grape diseases have established themselves, the vines should be drenched with the fungicide.
Pruning or burning infected canes.
This discourages the powdery mildew from developing. When the leaves of the vines are plucked, air movement increases and the duration of wetness of the soil reduce. This helps reduce further development of the grape diseases. Pruning also reduces the berry from splitting right after heavy rains.
Proper management practices.
Proper care and management of the vines reduces the damage of the grape diseases on the grapes. Irrigation should also be done carefully to minimize crown saturation.
This reduces the tightness of the bunches. Host species like old apricot tress should be removed from the vicinity so as to reduce the chances of spreading the grape diseases.
Drainage, Collecting and disposing infected leaves.
This reduces primary inoculums.
Drain the areas where the problem has erupted or wet areas where the grapes are planted. Poor drainage increases the chances of occurence of grape diseases.
Collecting propagation wood and root stocks
Propagation wood should be gathered from the vines that are not affected by fan leaf. The vine used to source the propagation wood should be from vines that had indexed free from fan leaf.
Use tolerant or resistant root stocks in the areas that have been infected with the grape diseases.
Symptoms of grape diseases
Shoots develop patches of soft brown rotLeaves develop fungus which grows from the edge of the leaf into the main veins producing a brown, V-shaped area of dead tissue. They also get oily spot that are yellow in colour and are translucent. The centre becomes dark and with yellow margins.Berries and bunches develop soft brown rotDecay. Under certain conditions of humidity and temperature, wine grapes infected with Botrytis decay slowly.Blotches. The first sign of grape disease can be blotches that are yellow-green in colour.Web-like growths. This occurs in the case of powdery mildew fungus. The web can only be seen under a microscope.Patches on the canes.Weak shoots. Some become black and are elongated with purple black margins.Inflorescence: the flowers or berries fall.
Sources and Citations