Weeping birch, known scientifically as Betula pendula Youngii, is also commonly referred to as Young's weeping birch or European white weeping birch. This specimen, a variety of European white birch, features white, peeling bark and has a weeping habit with no central leader. Weeping birches are very susceptible to insect problems that can affect leaf colouring. Yellowing foliage may also be indicative of a nutrient deficiency.
Weeping birch trees that do not have adequate iron or manganese may become chlorotic. Under these circumstances, leaf veins will remain dark green while the remainder of the leaf becomes yellow or light green. If the soil pH is too low or high, nutrients will become unavailable to the tree. Periods of high moisture, compaction and the presence of clay subsoils worsen the chlorosis. To treat iron or other deficiencies, adjust the pH as directed by the results of a soil test and consider spraying foliage with a chelated iron product.
Bronze Birch Borer
Weeping birch is extremely susceptible to the birch borer, an insect that can severely defoliate and kill trees. This small beetle has the greatest impact on already weakened trees. The earliest symptoms of a birch borer infestation are stunted or sparse leaves in the tree's upper canopy. Leaves may yellow and brown early and twig and branch dieback will occur. The entire dying process can take several years or can happen in a single stressful year. Insecticides and proper cultural practices may be used to prevent new borer attacks but cannot treat trees already in decline.
Unlike the birch borer, a leafminer infestation will not kill a weeping birch. Leaf miners can make a tree more susceptible to other pests or problems, however, and will affect the tree's attractiveness because they make foliage turn yellow and brown. Control leaf miners with insecticide applied as a foliar spray to the soil or painted on the stem. Multiple treatments are required throughout the leafminer life cycle for effective control.
If a birch has only been in the ground for a few weeks or months and the foliage is yellowing, improper planting technique could be responsible. Often weeping birches are planted too deeply -- the top of the root ball should be at ground level. To address a planting like this, pull some of the soil from the root ball so it is even with the surrounding ground. Too-frequent waterings may exacerbate the problem.