The Robinia tree, which is also known as the black locust, finds its origin in the Southeast United States, but it is now grown successfully in countries spanning the globe. With white blooms that cascade in thick clusters, this tree can add decorative beauty to any yard. As with all trees and plants, some Robinia tree problems can present themselves to unsuspecting home gardeners. Being able to recognise these problems can allow an individual to curb them before they become a real issue.
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Robinia Tree Pests
A number of pests can become problematic with Robinia trees, but the most common ones that cause the most severe problems are bark beetles and longhorned borers. Bark beetles feed on the interior side of bark and can cause limbs to weaken or break. Their damage may even result in the tree's death, and there is no chemical treatment. The only method of control is recognising weakening limbs and taking them down before the bark beetles have a chance to move on to the rest of the tree. Longhorned borers can produce holes in tree branches, thus weakening them and leaving them susceptible to breaking away. They can also cause leaves to yellow and die and even cause the tree to die. The best means of control is removing limbs that appear to be infested before the borers can spread.
Robinia Tree Diseases
Only two diseases pose a significant threat to the tree. Cankers are individual or a series of rotting spots along the tree's trunk or branches. Control them by pruning, using balanced levels of fertiliser and cutting cankers away as they appear. Powdery mildew is a disease that can be identified by powderlike spore clusters on leaves. It can kill leaves and obstruct normal growth patterns if it becomes a problem early on, leaving the Robinia tree shorter than the height it otherwise would have reached. A fungicide is the best means of controlling powdery mildew.
A number of parasitic plants can take the Robinia tree as a host and contribute to problems. Broadleaved mistletoe is the one that most commonly causes issues. It can infest Robinia trees and grow very rapidly. The primary damage mistletoe does is deplete the tree of essential minerals and water supply. The secondary damage is broken branches and perhaps even the death of the tree if the problem persists. The broadleaved mistletoe can be picked away as it appears or, if it has spread and got out of control, apply ethephon, a growth regulator, to get the mistletoe back to a level where it is not causing significant damage.
Certain conditions can prove to be obstacles to healthy Robinia tree development, and there is little that can be done about them after the tree has been planted. Fortunately, if these problems with growing conditions are taken into account before planting, you can avoid them. Rich, loamy soils are best for the healthy growth of Robinia. If the area the gardener lives in does not feature such soil, soil supplements can be purchased from a gardening centre. In addition, plenty of space must be allotted for the tree, as it has a large root system that spreads out more so than the roots of other trees as it grows. A lack of space and poorly drained, compact soil can stunt the growth of the Robinia tree and give it a generally unhealthy appearance.
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