Early Detection & Treatment of Spruce Needle Cast Disease

Some familiar evergreens such as Colorado Blue Spruce may be susceptible to environmental stress. The recent pattern of summer drought, milder than usual winters and cool spring temperatures combined with wet conditions in the northeast have favored development of a fungal disease known as “needle cast”. Early detection and proper diagnosis is important in the treatment of this fungal disease and to ensure the health of your plant.

Identifying Needle Cast

The best proactive means for preventing needle cast disease is to plant your Blue Spruce in the proper location and provide proper care. Blue Spruce prefer to be located in a well-drained soil in an area of full sun, meaning the plant should be receiving at least six hours of sunlight daily. A southern or western exposure suits this best. Prevent irrigation from directly spraying on the foliage of the plant. Constant moisture on foliage or over-watering can be a direct invitation for needle cast. Drip irrigation is recommended where possible, allowing the soil to dry between watering. Proper planting height is of course also necessary. Plant the tree at grade or slightly above the grade so that the root flare is visible. Do not plant too deeply. It is best that the lower branches have some air circulation above the ground.

The type of needle cast affecting Colorado Blue Spruce in the northeast is mainly Rhizosphaera needle cast (caused by the fungus Rhizosphaera kalkhoffii). While some browning and dropping of older needles in spruce is common, needle cast disease is noted by a distinct brownish-purple discoloration which appears on needles (usually towards the bottom of the tree) mostly in late summer, followed by the eventual death and dropping of older needles. In addition, the presence of black fruiting bodies on new growth in early spring is a sure sign. Typically, infections start near the bottom of the tree where foliage dries more slowly and progresses upwards. Lower branches may lose so many needles that growth at the tips stops, resulting in the death of the entire branch (photo below). Newer current growth may show no signs of the disease until during autumn and into spring.

Advanced Needle Cast Disease

Should your tree show signs of early needle cast, it is treatable. Needle cast can be effectively controlled with fungicides containing chlorothalonil. For moderate to severe Rhizosphaera needle cast, two properly-timed applications per year for at least two consecutive years (sometimes three) are required for control. After initial treatment, additional applications should occur when new needles are half elongated (around Memorial Day depending upon location) followed by a second application three to four weeks after the first. The timing of the two applications should be the same for the second and third year. Since needle cast is fungal and spread through spores, removal of branches showing early signs can prevent further infection, but the tree should still be treated with a fungicide and monitored on a regular basis.

The best method of preventing needle cast starts with proper planning, planting and monitoring. Early detection of any kind of disease leads to better results and remedies any further issues down the road. These tips also apply to dwarf forms of Blue Spruce, such as Picea pungens ‘Globosa’ (Globe Blue Spruce). Norway and Serbian Spruce are less likely to be damaged by needle cast and ‘Hoopsii’ and ‘Fat Albert’ cultivars of Colorado Blue Spruce are more resistant to the disease.

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Autumn Browning and Needle Shed on Hinoki Cypress: A Natural Process

If the inner needles on your Hinoki Cypress (Chamaecyparis) are suddenly turning from a healthy looking green to shades of yellow, orange and brownish-red in autumn, there is little need for concern. Needle shed is all part of a natural process. Each year evergreens will produce new foliage in spring and part of the preparation process involves shedding their older foliage in the previous fall. Shedding of needles and foliage is a process that evergreens go through as a way of preparing for new growth once the weather warms. As the days become shorter and temperatures lower, evergreens go through a slight dormant period similar to deciduous trees and shrubs. Many evergreens such as Chamaecyparis (Hinoki Cypress), Thuja (Arborvitae), fir, pine, cedar, hemlock and spruce lose some of their needles every year and may go through a major shedding every three to five years.

Autumn Browning and Needle Shed Hinoki Cypress

To examine, look at your tree carefully. Older foliage is shed first so the losses should generally be from the inside out and not at the tips. Prior to shedding the needles appear from green to yellow, orange and eventually brown, remaining on the tree until the process is complete. Often the change is unnoticeable; however, the drier the season, more drastic the temperature change, or stronger the winds, the more noticeable the needle shed, a natural cleaning process leading to new growth in the spring. If desired, lightly brushing the inner portion of the plant will help to remove the older browned foliage. If concerned about any particular branches on your plant, scrape the bark with your fingernail down to the growing layer. If the branches are brown and brittle the area tested has met its demise. If there is presence of a green growing layer underneath the surface of the bark, the branch is indeed alive.

 Author:  Lee@Landscape Design By Lee, 2019, All Rights Reserved

Browning and Needle Shed on Evergreens in the fall: A Natural Process

If your evergreen’s inner needles are suddenly turning from a healthy looking green to shades of yellow, orange and brownish-red in late summer and fall there is little need for concern…it is all part of a natural process. Each year evergreens will produce new foliage in spring and they prepare by shedding their older foliage in the previous late summer and fall. Shedding of needles and foliage is a natural process that evergreens go through as a way of preparing for new growth once the weather warms.  As the days become shorter and temperatures lower evergreens go through a slight dormant period similar to deciduous trees and shrubs. Many evergreens such as pine, cedar, Chamaecyparis (Hinoki Cypress), Thuja (Arborvitae), fir, hemlock and spruce lose some of their needles every year and may go through a major shedding every three to five years.

Fall Needle Shed on Hinoki Cypress and White Pine in late September-November-Shedding can be light or more pronounced. Lightly shaking the branches can help along the natural cleaning process.

To examine, look at your tree carefully.  Older foliage is shed first so the losses should generally be from the inside out and not at the tips.  Prior to shedding the needles appear from green to yellow, orange and eventually brown, remaining on the tree until the process is complete.  The actual amount of needle shed on the tree or shrub varies depending on the growing season, temperature changes and amount of rainfall, and can sometimes be sudden.  Often the change is unnoticeable but generally the drier the season or more drastic the temperature change the more noticeable the needle shed, a natural cleaning process leading to new growth in the spring.

 Fall Needle Shed on Evergreens Showing Previous Year’s Growth.  Older Growth is closer towards trunk.

Other species of evergreens in the broadleaf category can also shed their leaves.  Evergreens such as holly and laurel retain their leaves for only one year and rhododendron and azalea for one to two years.  Leaves will appear yellow before falling but at some times may go unnoticed if new leaves conceal old foliage.  This process usually occurs in spring when new growth is appearing but can happen at other times of the year as well.  If the whole tree or entire sections of your conifer are turning brown then there is cause for concern and you should have a certified arborist or landscape professional examine it.  Otherwise, fall yellowing or browning at the base or inner branches closer to the trunk seldom indicates a serious problem, but is more often part of the natural life cycle of the tree.

Conifer Annual Needle Shed

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 Author:  Lee@Landscape Design By Lee, 2014, All Rights Reserved