Why A Pear Tree Has Yellow Leaves
The most obvious cause of pear tree leaves turning yellow is, of course, autumn. If your days are getting shorter and nights are getting colder, that may be all there is to it. There are plenty of more troublesome causes though. Your tree could be suffering from pear scab, a bacterial disease that manifests itself in the spring with yellow spots that darken to brown or olive green. The disease spreads through splashed moisture, so remove and destroy all affected foliage, and water your tree in the morning when excess water will dry the fastest. Pear Psyllas, a small flying insect, may also be the culprit. These bugs lay their eggs on pear leaves and the babies, when hatched, inject the leaves with yellowing toxins. Spray petroleum oil on the leaves in late winter to deter egg laying. Your yellow pear leaves might also be caused by the stress of over or underwatering. Pear trees like infrequent, but deep, waterings down to 24 inches (61 cm.). Dig a foot or two (31-61 cm.) down in an area near your tree to get a sense of just how deep the moisture goes after a rainfall or heavy watering.
Yellow Pear Leaves Due to Nutrient Deficiency
Yellow pear leaves can also be a sign of a number of nutrient deficiencies.
If your new leaves are yellow to white with green veins, your tree might have an iron deficiency. Nitrogen deficiency brings on small new leaves and dropped yellow mature leaves. Manganese deficiency causes new yellow leaves with green bands and dead spots. Zinc deficiency sees long, narrow stems with clusters of small, narrow, yellow leaves on the ends. Potassium deficiency causes yellowing between the veins on mature leaves that can eventually wither and die.
All of these deficiencies can be treated by the spread of fertilizers fortified in your missing nutrient.
