Treatment for Crabapples

Crabapples produce one of the most prolific blooms in the springtime and produce a fruit desirable for wildlife. As a result, they are a highly desired tree in any landscape. The downside of owning crabapple trees is their susceptibility to a disease called apple scab. Apple scab is a disease that attacks both the leaves and fruit of crabapples causing leaves to drop in early summer. If left untreated, it can continually decline the health of a tree.

Fortunately, apple scab can be controlled with fungicide treatments. However, the timing of these treatments is very critical. If you are aware of apple scab damage from the previous year, it is imperative you schedule a treatment.

The first spray should be done as the leaves are emerging. This is referred to as “bud break.” Follow up treatments are performed every 10-14 days after initial spray, with an average of 3 sprays during the spring. If you wait until symptoms appear, it is too late. It is also important to note that these applications must be done every year because they are a control, not a cure. There is no cure for apple scab.

Treatments for Austrian and Scots Pine Diplodia tip blight is a disease that affects Austrian and Scots Pine. Timing of this series of treatments is very critical too. The first spray should be done as the “candles” (tip of branches where new growth happens) start to emerge. The next 2 treatments are completed 10-14 days apart. If untreated, this pathogen can move beyond the tips and form cankers in the stems and trunks; therefore, causing more damage to the trees and eventually causing the tree to die. Knowing the severity and spread of the disease on your property will help determine the best course of action. In some cases, it may be more economical to remove and replace with varieties of trees that are not susceptible to Diplodia.

Zimmerman Pine Moth

Another treatment to consider in Austrian and Scots Pine is controlling of Zimmerman Pine moth. There are only 2 treatments required, one in spring and one in late summer. Timing is also critical with the treatment because you are targeting an application before the larva has a chance to form into a caterpillar.

Tree Health Tips and Tricks

An important message to consider with all applications is that your plant health care provider should not perform sprays based on the calendar. Your provider should be basing applications on growing degree days. This is a system well documented in a publication called “Coincide” written by Don Orton. The schedule of applications is based on a formula that takes the high and low temperature each day. It also uses indicator plants (phenology) as a guide to when you should do your treatments. Timing of controls change every year based on the weather.


Another helpful healthcare tip for spring is to develop a monitoring schedule for your trees. One way to do this is by scheduling a spring visit with a certified arborist. After a season of violent winter weather, it is vital to have your trees checked by a certified arborist for damage. Hanging branches and major deadwood can be a liability and if unchecked, could cause harm to homes or individuals.

An essential function of your monitoring schedule is a pruning program for your trees. Pruning trees in late winter or early spring, is an optimal time to prune. Pruning during this time is easier because the structure of the branches are visible, clean-up is less time consuming, and it reduces cost.

Don’t forget to prune your young trees! If proper pruning is not performed on trees from a young age, it will lead to irreversible problems.

Proper pruning saves time and reduces cost while guaranteeing the long-term health of your trees.

According to Dr. Ed Gilman from the University of Florida, other principles of creating strong structure in young trees include:

• Eliminating co-dominant stems.

• Removing narrow angled V-shaped branch unions and leave U-shaped unions which are stronger. • Removing/preventing included bark.

• Removing a few of the lowest limbs but others are temporarily left to help the trunk develop more taper and strength.

Additionally, the Arbor Day Foundation recommends: • Cutting off root suckers and sprouts in the crown.

• Thinning excessive branches to reduce competition for light, water and nutrients.

There are many ways to ensure the trees in your community are healthy. It is always important to consult an arborist and have an inventory completed. A tree inventory will tell you the diversity of species you have in order to develop a comprehensive plan to fit the specific needs of your community. It is imperative to take consultation from a professional to make sure you are properly managing your urban forest.

• Spring 2020 • A Publication of CAI-Illinois Chapter

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