By: Zvi Howard Wener / Chief Agronomist / Zviw@zeraim.co.il

Israeli pepper crops that are planted in greenhouses and nethouses during the summer are covered with black shade-cloth immediately after planting. Israel has a Mediterranean type climate with very hot and dry summers. Crops that are planted during the summer months have to endure temperatures of 35°C and higher, as well as high levels of light radiation - around 2000 micro-einsteins (photoactive radiation).

High radiation causes air and leaf temperatures to be much higher than the optimal temperatures needed for good balanced plant growth. Therefore, after transplanting, black shade-cloth reduces the light radiation. The total shade (shade-cloth + net or plastic roof) is between 40-50% and the shading reduces the air temperature and the amount of light available for photosynthesis.

The new artificial conditions of more moderate temperatures and much lower light greatly reduce the stress on the plants after planting. The leaves grow bigger than they would in full light because of an increase in cell division in the developing leaves. The relatively low light levels usually cause flower drop and the plants have a good fast start in vegetative growth. Most varieties require the shade-cloth for a period of 25-30 days but this can vary with the variety and local environmental conditions. When it is time for the flowers to pollinate, the net is removed and the sudden exposure to full sunlight causes the plants to be under stress and the plants go from a vegetative to generative state. Flowers remain on the plant and begin pollinating. At this stage, it is important not to allow the plants to become too vegetative.

Later in the season, when the crop is being harvested, the winter/spring sun can be too strong for the fruit on the plants.

Shading at this time of year can help slow down fruit growth and ripening and protect the fully developed fruit from sunscald and other disorders such as blossom-end-rot.

Shading during planting Shading to protect fruit