Tag: evergreen

Identifying Diplodia Tip Blight in Pines

Diplodia tip blight is a disease of pines in the Midwest area and the treatment window will soon be upon us. This disease is caused by the fungus Sphaeropsis sapinea and highly effects two-needled pines such as Austrian, scotch, mugo and red, but can infect all evergreens. Here, our Austrian Pines are the most affected and are no longer planted here.

pine with blight on needles

The disease will eventually kill the tree, but can take a long time, without treatment (5 years-ish). Although treatments can slow the process, careful thought is needed in a budgetary sense. The tree will begin to have die-back (larger branch death) and will require regular pruning to be aesthetically pleasing… if that’s even possible. Treatments can be costly, worse-case ineffective, if not applied correctly. The cost of removal will go up as the tree gets larger or becomes more hazardous to fell. In the end, depending where the tree is located, along with the ‘value’ placed on the tree, it may be more cost-effective to remove the tree and replace it as soon as diagnosed.

blight on pine needle

The Diplodia fungus overwinters on infected needles, cones, and within the bark of twigs. Spores are released from spring through late fall. New shoots are infected during the spring from bud break to the end of the growing season. The cones are infected during the spring of the second season, as it takes two years for cones to mature.

Spread of the disease is by the splashing of water, be it rain or over-head irrigation. Because this disease tends to overwinter and spread from infected cones, symptoms are first noticeable on the lower branches, as old cones collect under the tree. Symptoms of infected trees become visible in summer through fall and resemble stunted needle growth and yellowing. Spores can be seen on the needles & old cones as black dots. Because cones are more susceptible to infection, younger, non-cone bearing trees are often symptom-free.

Managing Diplodia tip blight focuses on tree health and sanitation. Providing proper care such as no overhead (and proper) watering, mulching, pest management and fertilization, helps suppress the disease. Removal of diseased cones from the ground helps, but is not practical in large stands of pines. Pruning of infected tips will aesthetically improve the tree, but will do little in the stop of the disease.

Severely infected trees should be removed. A fungicide spray program needs to be implemented in the spring and includes at least three applications. Make the first application just prior to bud break* (which will be soon) and make two additional applications at 10-day intervals. It is important to get the first application on the trees before any bud sheaths have broken (the papery tan cover). If the tree you’re trying to save is of high value, consult a licensed ISA arborist, as the chemicals available to professionals are usually more effective.

* Indicator plants to watch for blooming that coincide with bud break:

  • Spiraea x vanhouttei – Vanhoutti Spirea
  • Cercis canadensis – Eastern Redbud
  • Chaenomeles speciosa – Quince
  • Syringa vulgaris – Common Lilac

© The Naturarian

Winter Damage on Evergreen Trees and Shrubs

Winter damage on evergreen - looks red or burnt

Winter burn happens when plants dry out during the winter. Even during the colder months, evergreens continue to lose water vapor through their needles, which are modified leaves. The plant attempts to replace the water by pulling it from the roots. However, when the ground is frozen, the roots cannot absorb enough water to supply it to the dry needles. If the weather turns breezy, warm and sunny while the ground is still frozen (like today, in the Midwest), evaporation from the needles increases and water cannot be replaced fast enough. Discolored, brown or burnt-looking foliage may start to appear when this happens. In fact, winter burn indicators typically develop during warm weather in late winter and early spring.

Winter damage is often misdiagnosed as a disease or as damage from excessively cold temperatures. The damage which starts at the tips, is brown or rust-colored and generally on the side of the plant facing the sun and/or the side exposed to the wind, where the rate of evaporation from the needles or leaves is greatest.Dense yew evergreen with rusty looking winter damage

Winter burn can be more prevalent in years in which the ground freezes early before plants are acclimated to cold weather or when there is little snow. Without snow cover or mulch to insulate the soil, the ground can freeze more deeply. Although this is not always true, as the amount of snow did not matter this year because of the frigid temperatures, the ground is still frozen about 2 feet down.

Light pruning can remove the burn, however some lazy gardeners (ahem… the author) wait for the needles to completely dry and brush them loose / let them fall a bit later in the season.

Winter Burn Management Strategies

azalea evergreen leaves with rust colored winter damage on leaves

Water well in fall: One inch per week or saturate to the depth of 12” to 18” inches. Watering should be continued through late autumn into early winter as long as the ground is not frozen.

Mulch: Use mulch around the plant so the entire root zone is covered. This will reduce moisture loss.

Build a barrier to wind. A burlap barrier can deflect wind from the plant.

Promote good culture. Monitor the amount of moisture in the spring when the plant is coming out of a period of frozen ground, and low moisture availability. Water as needed if the rainfall is less than an inch per week.

Many broad-leave evergreens such as: holly, boxwood, yews and rhododendrons will also have some winter burn this year.

 

© The Naturarian