Larvae, nymphs and adults cause damage to the host plant by feeding on plant sap. They mainly occur on the underside of leaves where they pierce the cells and suck out the contents. The empty dead cells become yellow, and in many plants the damage can also be seen on the upper surface of leaves as small yellow dots. The destruction of cells results in reduced photosynthesis, increased transpiration and reduced plant growth. As damage increases, whole leaves turn yellow, and as more cell sap is removed, the leaf, and eventually the whole plant, may die. In tomatoes and cucumbers, as little as 30% damage of the leaf surface can lead to loss of the crop. The nymphs and adults also produce webs, and plants can get completely covered with such webs in which the mites live. The webbing and spotting on the leaves affects the appearance of the crop. This is of particular concern in ornamental crops.