Summer Can Be Stressful For Your Trees

Julene Reese

While it is widely known that humans experience stress, many homeowners forget that trees also experience stress. And, unfortunately, most of the stress is not created by the tree.

“One of the common stresses we put on trees is changing the water pattern,” said Jerry Goodspeed, Utah State University Extension horticulturist. “This occurs most commonly by over- or under-watering, which is fairly easy to detect. Other moisture level changes are not as easy to spot. A change in the groundwater level can occur through upstream building or through an altered drainage corridor from downstream road construction. Drought also alters soil moisture, and its damage may go unnoticed by a homeowner for some time.”

Any type of construction around trees also impacts them, said Goodspeed. Homeowners often fail to realize how far a tree’s roots extend. A neighbor putting up a shed, laying a new driveway or taking out an area of lawn to put in a hot tub or patio can affect a tree 100 feet away. If feeder roots extend into the construction zone, the tree is stressed while adapting to the new environment.

Another problem for trees is if the grade of the area around it is changed, he said. Many noble trees have died because the homeowner decided to develop a 12-inch high raised bed around its base. This not only alters the tree’s oxygen and water ratio in the soil, but also increases the moisture at its base, making it vulnerable to root rot and decay.

“Any change in grade around a tree can affect its growth, even cuts and fills several feet away,” said Goodspeed. “When roots are cut during landscape renovation, part of the tree’s water and nutrient supply is removed. Although most trees survive minor grade changes, it causes stress and leaves them susceptible to insect pests and diseases.”

Another stress often overlooked is increased competition, he said. The thicker, more mature a landscape becomes, the more competition there is for existing water and nutrients. We forget that as a tree ages, it requires a deeper, more plentiful water supply. Simply sprinkling the lawn may be enough for a small, newly planted tree, but will not provide adequate water for a mature, 40-foot shade tree.

“Many trees are planted in close proximity to each other when they are small, cute and cuddly,” said Goodspeed. “However, as they reach those troublesome adolescent years, they start fighting over the available water and nutrients. When this occurs, weaker trees often slowly decline as they lose the battle. Then pests and diseases move in to finish off the job.”

Another stress put on a tree is limiting its root spread.

“This occurs when we plant a large tree in a small space, kind of like forcing a large basketball player into a small Yugo,” said Goodspeed. “He may stay there for a while, but eventually will get tired of being cramped and go out and purchase a Hummer and a couple of homes. Most trees can’t purchase more space or move, so they get weaker and slow their growth. This is a common phenomenon in trees planted in small parking strips next to sidewalks.”

For a healthy tree, reduce as many of the known stressors as possible, he concluded. Keep in mind that a declining tree may not be suffering from a plague or pests. It could be suffering from homeowner mismanagement.

Protect Your Berry Harvest
By Monitoring Fruit Eating Insects

Julene Reese

About the time local berries reach maturity and are ready to be picked, fruit-eating insects show up to reap the fruit of growers’ labors. Common fruit-eating insects in Utah include the stink bug, lygus bug, earwig, grasshopper and several species of fruit-eating wasps.

According to Diane Alston, Utah State University Extension entomologist, damage occurs when the insects suck or chew the individual drupelets and sometimes even remove the entire fruits.

“To help prevent economic yield loss, growers and home gardeners should inspect ripening fruits several times a week,” she said. “They can place a cloth or plastic tray under the plants, then shake the canes to dislodge insects. If damaging insects are found, they can be removed by hand or sprayed with an insecticide. If insecticides are used, it is important to read the product label to determine the pre-harvest interval or required waiting time between application and picking fruits. There are also plant cultural practices that can reduce the abundance of fruit-eating insects.”

Recommended insecticides with low toxicity to humans are neem oil (Azatin) and spinosad (Success, Entrust). Conventional insecticides that deter fruit feeders include carbaryl (Sevin), malathion, permethrin and esfenvalerate.

Utah residents who need help identifying berry-eating insects or information on pest management can contact Utah State University Extension and the Utah Plant Pest Diagnostic Lab, Alston said. It is important to accurately identify insect pests in order to manage them.

The Consperse and green stink bugs are one-half to five-eighths inches long with a shield-shape, flattened body. The Consperse stink bug is speckled brown with pointy “shoulders” and the green stink bug is a bright green color. Both stink bugs feed on individual drupelets and cause them to shrivel. They release an offensive odor and contaminate the berries at harvest.

Lygus bugs are one-fourth inch long, green and brown in color and are attracted to flowers and developing fruit. They cause misshapen fruit by feeding on individual drupelets. They are usually present at low density and do not cause economic damage to raspberries.

European earwigs are one-half to three-fourths inch long, shiny brown and have a pair of claspers at the tip of the abdomen. They are nocturnal and their presence or damage may go unnoticed until harvest. Earwigs feed on fruit and foliage. To manage them, remove weeds from around the base of canes and vines. Keep rows clear of debris. Earwigs can be trapped by using Tanglefoot® or a similar adhesive at the base of canes to prevent them from crawling into plants. To monitor for them, place boards or rolled-up newspapers next to berries in spring and check weekly for hiding earwigs. Treat the ground and lower canes with carbaryl at the beginning of spring activity when earwigs are found.

In areas where berry fields are located near open rangeland or undeveloped land, grasshoppers may move onto canes at harvest time to feed on fruits and leaves. Fruit-protecting insecticide treatments may be effective. Insecticide bait (bran coated with carbaryl or Nosema locustae, a protozoan biological control) placed around field borders when young grasshopper nymphs are first seen may reduce populations. Repeated bait applications will likely be necessary, but it is important to note that insecticide baits are not effective at killing adult grasshoppers.

The yellow jacket and European paper wasp are common berry eaters that also sting those who disturb them. Yellow jackets nest in the ground, and nests can be treated with conventional insecticides, dug up, removed and destroyed. Placing commercial traps that contain heptyl butyrate bait at the perimeter of berry fields can also reduce yellow jacket numbers. The European paper wasp builds umbrella-shaped nests under the eaves of buildings and other protected sites. Paper wasps are not attracted to yellow jacket traps. Removing nests and protecting fruit with insecticides near harvest may provide control.

USU Extension has offices throughout the state, and local Extension agents can assist with pest identification and insecticide use. The Utah Plant Pest Diagnostic Lab, located on the USU campus in Logan, provides pest diagnostic services and pest management education for commercial growers and homeowners. Sample submission information is available at http://utahpests.usu.edu/uppdl and information on other Utah pests can be found on the USU Extension Utah Pests homepage at http://utahpests.usu.edu.