Training

De-leafing
When vines are lowered, leaves touching the ground are removed to prevent disease development. The amount of de-leafing that occurs higher up the plant varies between growers. The purpose of de-leafing higher up the plant stem is to increase light penetration and air circulation. Typically, all leaves are removed below the lowest fruit cluster which has not been harvested, but when a new crop is intercropped next to the old, deleafing may be more severe (Fig. 8).

Deleafing is also thought to make more carbohydrates available to other plant parts, thereby increasing yield, but there is little or no experimental evidence for this. Another factor to be considered in deleafing is the effect on pests and beneficials. Removing lower leaves from the greenhouse and then destroying them will also remove whitefly immatures developing on lower leaves. However, if beneficials have been introduced, they will have parasitized the immatures, and removing and destroying leaves will also prevent the beneficial from emerging. Sometimes if beneficials are known to be present, leaves are removed, but left piled in the greenhouse for a few days to allow emergence. In this case, deleafing and leaf removal represent a tradeoff between emergence of whiteflies, emergence of beneficials, and spread of disease from the discarded leaves.

Fruit Pruning
Small, undersized fruit at the end of a cluster (distal fruit) are always removed, as these will generally not grow to marketable size and are thought to reduce the size of the other fruit on the cluster. In some cases, all clusters are pruned to leave only the 4 fruit nearest the plant (proximal fruit). Whether or not clusters are pruned depends on the expected fruit size for that cultivar, how many fruit normally form on the cluster, growing conditions and the size demanded by the market.