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Trees are showing a life cycle of August in July. The weather pattern of 2012 is giving us a season about 30 days earlier than the typical season. As a result, the vegetative world as we know it is experiencing the climatic changes of August in the month of July. The trees are showing stresses usually associated with August and are also susceptible to other insects and diseases.

Leaf scorch has been visible in many species of trees. The margins of the leaves often roll inward, followed by browning and death of the tissue. Trees use large amounts of water on a daily basis during the growing season. Adding water beyond the one and one half inch necessary for lawn growth each week is recommended. Remember, the majority of new root zone is along the drip line of the tree, not at the trunk of the tree.

Spider mites are currently damaging numerous woody plants. Blue Spruce, Fir trees, Arbor vitae and Alberta Spruce are especially susceptible Damage symptoms progress from stippling to yellow, browning to death of the tissue. Mites are living on the bottom of the leaf. To check, place a piece of white paper under a branch or leaf, tap it with your finger and look for little specks of dust that move when exposed to bright light or heat. Since these mites are very tiny and do not like cool areas, a stiff hosing of water repeatedly shot into the tree not only washes the mites down, but also creates a negative environment for reproduction

Spruce needlecast on Colorado blue spruce is caused by Rhizosphaera fungus. Infected needles turn reddish brown and develop rows of tiny black dots visible under magnification. Control by spraying a compound containing chlorothalonil.

Carpenter ants often nest in the dead wood of standing trees, as well as tree stumps and firewood. Carpenter ants are the largest ant found in Nebraska, usually measuring from oe-fourth to five-eighth in long. Carpenter ants do not eat wood, but take advantage of the dead wood as a nesting site. Adding carbaryl to the nest every two weeks until controlled is recommended.

When replacing or planting new trees, choose species that are well adapted to Nebraska’s extreme climate conditions. Also, the planting of the same species in large numbers is being replaced with an attitude of diversity, planting groups of 3 or 5 of a species. This is essential in pest management.

Homeowners should be aware of the potentially serious problems caused by Emerald Ash Borer. Though there are no confirmed reports of the borer in Nebraska today, knowing it will arrive in a few years is a warning not to plant any Ash trees at the present time. The same warning exists in planting any Scotch Pine trees until a method of controlling the Pine Sawyer beetle has been proven. These recommendations will reduce added expenditure of money for future removal and time (years) it takes to replace a tree.

Twig girdlers are appearing. These insects, in their adult stage, chew cylindrical rings around new growth branches. Damage shows small clusters of brown leaves on twig tips. Thus far, no recommendations for chemical spray are advised. Many times the effect of the twig girdler is mistaken for the same chewing action bestowed by the squirrels. Squirrel chewing is not the neat visual given by the girdler. No-one seems to have the cure for squirrel control, especially if someone in the neighborhood feeds them during winter months.

 

About the author: Don Siffring

Don Siffring is a 6 year Master Gardener with the University of Nebraska Extension in Adams County. He is a professor emeritus with the University of NE, Institute of Agriculture. Don works part-time as a Horticulture Aide with UNL Extension in Adams County. Don and his wife, Bev, retired to the Hastings Community in in 2003 to be closer to their married daughter and husband, Christi and Brian Berns of Bladen.