What Causes Trees To Have Empty Leaf Spots?

Leaves are a crucial part of a tree’s anatomy and ultimately determine the fate of the tree. Leaves facilitate the process of photosynthesis. They use the energy from the sun to create fuel/food for the tree ensuring that the tree has sufficient nutrients and air to help it stay healthy and grow. Leaves are also an excellent indicator of how well your trees are excelling, so what happens when your leaves have empty spots? 

There are various reasons why your trees could have empty spots instead of leaves. This could be an indication of malnutrition, insect infestation, or soil compaction. The tree could be responding to unfavourable weather conditions. Unfortunately, the answer is not as simple as it seems since all trees are inherently different. Various factors can deny a tree from having a wonderful full canopy. In order to get to the root of the problem, one has to evaluate the tree carefully to find the underlying symptoms. 

If your trees have empty spots, it might be because of the following reasons:

Borer insects

Wood-boring insects are among the most destructive pests when it comes to trees. They tunnel and feed under the bark of trees, destroying water and sap conducting tissues. This causes ringbarking, branch dieback, structural weakness, decline and even death. These infestation sites also provide entry points for plant pathogens. A clear visible sign of borer insects are spurts of tiny holes in the trunk and empty spots in the canopy.

Borer insects seldomly infest healthy trees that grow in their indigenous environments. However, when trees are transplanted into a landscape, stresses such as soil compaction drought, sunscald/injuries can weaken them, making them more susceptible to pest attacks. Properly timed bark sprays with contact insecticides can prevent the infestation of vulnerable trees. Pyrethroids including bifenthrin and permethrin are also effective. Chlorantraniliprole is a suitable option since it is bee friendly. Contact insecticides require proper timing in order to intercept newly hatched borer insects that tunnel into the bark. The tree trunk and main scaffold limbs should be sprayed first to prevent further damage. 

Weather-related stress

Empty spots on trees can be a sign of stress due to harsh weather conditions. Tree leaves can undergo stress due to salt damage, wind damage, and insufficient water. The sudden drops in temperature in winter can cause damage to trees that have not acclimated. Extremely cold weather can shock some parts of the tree more than others. Areas with sparse leaves may struggle to recover from winter elements thus causing empty leaf spots. Drought and wind are factors that are accompanied by high temperatures. Different tree species show different signs of heat stress such as empty leaf spots. 

Rapid climate change can also affect a tree’s growth rate and mortality rate. Unfavourable soil and air temperatures decrease chemical activity and reduce growth in trees. Watering recommendations may vary with regards to the ideal time to water your trees, but deep watering is generally recommended over shallow watering. Watering your trees during the morning is often prescribed in times of high temperatures. It’s imperative to remember that shallowly rooted trees often dry out more quickly and tend to suffer more easily. Younger trees with less-developed root systems require additional water more often than older trees.

Mulch can be highly beneficial to trees, especially in times of unfavourable weather conditions. Mulch conserves moisture in the soil by reducing evaporation and minimizing temperature fluctuation. This is highly recommended for preventing empty leaf spots.

Soil compaction

If your trees have empty leaf spots this might be a sign of soil compaction. Soil compaction occurs when soil particles are pressed together, reducing the pore spaces between them. This decreases the rate of water infiltration and drainage. Compacted soil makes it difficult for water to flow through to the tree roots, causing runoff and dehydration. The compacted soil causes the roots to receive insufficient nutrients thus leading to decelerated growth. The lack of water and limited airflow prevents the trees from thriving which can cause empty leaf spaces. 

Since compaction often occurs in a layer below the soil surface, it is not easy to identify. A great test for soil compaction is pushing a screwdriver deep down the soil. If it’s difficult to do it, it means that the soil is compacted. You can also cut out a chunk of soil, if your soil is dull, greyish and very dry, it means your soil is compacted. Fortunately, soil compaction is a minor problem. This can be easily solved by mixing compost into the top 20cm to 25cm of the soil to add a surge of nutrients. Soil compaction can also be reduced by avoiding wet soil. These are the most susceptible to compaction because when it’s wet it gets saturated and can no longer absorb any more water. You should also use the appropriate equipment since the degree of compaction is determined by the moisture content of the soil. 

These are just a couple of reasons why your tree may have empty leaf spots. The tips above can help you ensure that your trees grow healthy and produce a full canopy. Always remember that sourcing the best trees is truly the only way to increase the probability of having well developed and fruitful trees. Just Trees has a wide variety of trees suitable for all types of landscape projects, visit www.justtrees.co.za to make your purchase today.

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