What comes after April showers?
Written by: Kyle Babicky
We are close to turning the page on another Wisconsin winter. On the horizon is emerging a season that many of us look forward to – Springtime and the beautiful blooms that come with it! Some of the most majestic bloom performances in spring come from the wide variety of crabapples throughout the area.
During this wonderful time of the season, there lurks an invisible enemy. Many of you are all too familiar with this pesky invader, a fungus called Apple Scab. Luckily, apple scab does not harm the blooms in spring. However, seeing a tree that looks so beautiful can distract us from noticing there is a disease already taking hold.
When apple scab infects a tree, it is not seen until it is too late to correct for the year. The result is often a mostly bare tree and leaves scattering your yard only halfway into summer. The tree also loses several weeks of making food and energy for itself. Losing leaves early each year will cause stress on a tree.
The trick is to be proactive with apple scab. The time to begin protection is when we are eagerly awaiting the spring blooms. A properly timed treatment program each year is the best defense in helping your crabapple keep its leaves until fall. If you receive a customized annual Tree Care Prescription letter from our team of certified arborists, your early approval allows us to properly time your treatments.
Apple Scab is an annual disease. This means there is a new generation of spores every spring ready to infect new leaves. This means a tree must be treated each year to keep apple scab away. A silver lining here is that one season of apple scab will not kill a tree. If your crabapple tree had apple scab last year, you can keep it from infecting new leaves this spring.
Proper treatments are the top priority in defense against apple scab, but the following factors play a large role as well:
- Properly spaced branching helps to increase sunlight and airflow throughout a tree canopy. This allows for leaves to dry faster, resulting in better conditions to resist disease. Proper branch spacing can be achieved through professional pruning. A good pruning cycle for crabapples is usually three years depending on age and cultivar.
- Overall tree health is also important in resisting tree diseases. Healthier trees often have thicker leaves, which creates a better “wall of defense” against diseases. It is a good idea to have trees routinely inspected by a certified arborist to determine if there are issues with your tree that could make it more vulnerable to infections.
- Weather – No one has control over Mother Nature, but rain, wind, humidity, and temperature all play a major role in tree health. Trees need adequate soil moisture, but long periods of wet leaves mixed with warm temperatures (generally above 50ºF) allow apple scab to take hold. Also, arborists need to work around weather factors, such as rain and wind, to perform quality treatments.
Another factor to consider is the DNA of a tree. Some crabapple varieties are naturally resistant to apple scab. No crabapple is immune, and resistance can fade over time, but some crabapples are resistant enough that their symptoms from the disease are minimal. If you are looking to plant a new crabapple, it is recommended to consult with a certified arborist to choose a variety that has higher disease resistance.
If you’ve experienced Apple Scab on your trees in the past, or are interested in having your crabapples evaluated, please give us a call! We are happy to help provide tips for you to keep your trees thriving in the landscape.