These may damage the fruit directly, making it unattractive or inedible, but also weaken the pome fruit tree by injuring or invading the leaves, trunk and branches. Damage to the pome fruit trees reduces productivity and increases susceptibility to winter injury or attack by additional pests.
The most common diseases are rust, scab, different rots and fire blight. Fire blight is the greatest limitation to European pear production. Attacks from a variety of insects and mites are frequent too. Good crop nutrition is essential to promote the health of pome fruit plants and make them more resistant to pests.
It is important that potassium concentrations are in balance with other cations, particularly calcium, as preferential uptake of potassium over calcium will significantly increase the risk of rotten fruit and physiological disorders.
Storage rots including Gloeosporium rot and penicillium can be minimized by use of calcium. Repeated foliar applications are the most effective at alleviating this kind of damage.