Summer provides many challenges to trees, from heat and drought, to attacks by other living things. Many things are beyond our control, but there’s a lot we can do to help our trees. Watering and providing good soil for a tree to grow in can help boost the tree’s natural defenses. Some issues, especially non-native invasive insects and diseases, mean trees will need more active assistance from us.
Like all other living things, trees can be susceptible to disease. Over many springs and summers, the rain and wind can spread bacteria and fungi from one surface to another. This includes the leaves of the trees in your yard. Bacteria and fungi can also reside in the soil, attacking roots. Whatever the cause, it’s essential to know how to identify a disease, prevent it, and treat it to save your tree and stop the issue from spreading.
Throughout the summer months, there are some things you can do to ensure each of your trees is healthy and ready for the summer ahead. Here are some tips on preparing a tree for summer to ensure it thrives — not only this summer, but for many summers to follow. To better understand how to spot and prevent tree issues, it can help to look at those diseases and insects that are most likely to impact your landscape.
Perhaps best known as a disease that affects crab apple, apple, pear, and serviceberry trees, apple scab is a fungal disease that can spread to both the leaves and the fruit. When a tree is exposed to cool, damp weather and cloudy conditions in the spring as leaves are starting to bloom, an apple scab infection is more likely to develop.
In early summer, you’ll first notice an apple scab as a dark splotch that looks like watercolor paint spreading on paper. Over the summer, the lesions grow and can eventually kill the leaves. Some leaves will also turn yellow in the process, but not all.
Insects can carry disease too. Fire blight occurs when insects are attracted to substances that ooze from infected trees and then carry that infection to other trees. Wind can also carry the infection. It’s essential to catch a fire blight infection before it reaches the trunk of the tree.
To spot fire blight, keep an eye on a tree’s leaves. Infected trees will have leaves that droop as though weighted down after a heavy rainstorm and will even start to shrivel. As the disease progresses, they’ll turn brown and crispy, and the bark will look cracked and burnt.
Oak wilt is a fungal disease that affects the water-conducting vessels of oak trees. The disease can spread from one tree to another through connections between tree roots called grafts. It is also spread further distances by small beetles, which pick up spores from infected trees by feeding on the sap that comes out of fresh wounds. They then deposit spores on wounds of uninfected trees. This is why we don’t prune oaks during the spring and summer: fewer wounds, less chance of oak wilt transmission.
Although oak wilt can affect all native oaks, symptoms can differ. The infection will spread quickly in red and pin oaks and is generally not treatable. In bur and white oaks, leaves will take on more of an autumn appearance, with some scattered discoloration and wilting. If we suspect oak wilt in a white or bur oak, we can take a sample and have a lab evaluate it prior to making a treatment decision.
When considering how to prepare a tree for spring, it is essential to rule out whether or not insects have made a tree their home. Here are three common types of tree insects found in the spring.
Going by the scientific name Agrilus planipennis, emerald ash borer attacks can kill all our native ash trees. With over a billion ash trees in Minnesota alone, this is an insect that has already created significant devastation for our tree population. As the infestation progresses, the ash tree’s condition deteriorates, and branches break. When it gets bad enough, trees must be removed to prevent them from failing and hurting people or property.
Emerald ash borers leave holes as they exit the tree; if you look closely, you might see small D-shaped holes. The bark over the larval galleries will die and sometimes split open, revealing S-shaped tunnels beneath the bark.
If you have conifers, check for signs of spider mites, which feed on the fluid inside the needles. Each year, multiple generations of spider mites appear, with each generation lasting 15 to 20 days. Since spider mites feed on the oldest needles first, look at the most mature needles and pay attention to signs of speckling or flecking. As feeding progresses, those needles will begin to brown and can fall from the tree.
Pine trees are susceptible to pine needle scale, found on pines, Douglas Fir, spruce, and Juniper trees. Scales remove the sap from pine needles, damaging cells in the process. Search for white scabs on the needles and the plant’s stem when looking at how to tell if your tree is infected.
Tree fertilization is also an important consideration, and that starts with your soil. Many homeowners choose to aerate their lawns each year to keep turf roots healthy; trees can benefit from a similar but more extensive process using compressed air. While we’re breaking up the compacted soil, we can add an organic, slow-release fertilizer. In forests, fertilization happens naturally as fallen leaves and other tree debris are broken down and decayed. This process occurs much less in landscaped areas, meaning your trees lose some of this natural fertilization cycle. Adding nutrients and organic matter to the soil can help provide your trees with the best possible soil to grow in, keeping your trees looking and growing great.
Vineland Tree Care is one of the leading tree companies in the Twin Cities metro area. If you’re wondering how to prepare your tree for fall, give us a call, and one of our certified arborists will talk with you about your and your tree’s specific needs. Or request an estimate for tree fertilization or other work you’d like done. We can’t wait to prepare your tree for fall.
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