FAQ: Environmental and Insect Damage

FAQ: Environmental and Insect Damage

  • By mid summer you should see a brown to greyish discoloration towards the inside of the tree. Fine webbing should be noticeable around the twig and half way up the needles.
  • If webbing is seen on the outside portion of the needles it is ordinary spiders, which are beneficial.
  • Registered products include malathion, Kanemite and Basudin (rates on label). Spraying with a strong blast of water several times during the growing season will reduce spruce spider mite populations.
  • The ash plant bug causes a stippling effect on the leaves of green ash.
  • This pest is more of a problem on ash trees under 15 years of age. Damage can result in severe defoliation and possibly death of young trees.
  • Registered products include: carbaryl (rates on label).
  • Yellow-headed spruce sawfly can cause severe defoliation of spruce in late June to early July.
  • ​The damage is most noticeable on new growth near the top of the tree. Larvae are green in color with a yellow to tan color head and are 25 mm in length.
  • Registered products include: acephate, carbaryl, malathion and permethrin (rates on label).
  • There are three tent-forming caterpillars: Prairie tent caterpillar, ugly nest caterpillar and fall webworm.
  • ​On young trees, these insects may cause severe defoliation and reduced growth, whereas on older established trees the damage mainly affects the appearance rather than its health.
  • Numerous products are available for control of these pests: carbaryl, malathion, diazinon and Bacillus thuringiensis (rates on label).
  • Damage from these tent-forming caterpillars can be reduced by removing and destroying tents.
  • There are many species of aphids attacking nearly all species of plants.
  • Aphids may be found on the leaves, stem, twigs or roots of plants. They are small, soft bodied, pear shaped insects that vary in color.
  • Aphids cause damage by sucking the sap from the plant with their piercing mouth parts. The feeding action of aphids will weaken the host but will not cause permanent damage.
  • There are numerous products available for control of aphids.
  • First, it is necessary to try and get a good general assessment of the situation. Some things to look for are soil type and moisture ranking in the soil profile.
  • ​Also consider the location of the tree planting. Some possible causes include:
  1. winter browning caused by needle desiccation during warm winter days,
  2. lack of moisture at rooting depth for safe over wintering,
  3. spring/summer drought impacts, and
  4. insect and disease pests.
  • Exposure of conifers to flooding, spray drift or soil contaminants may cause problems.

Browning of older spruce is generally a combination of several factors including:

  • Age – Colorado spruce have a life span of 65 to 75 years, whereas white spruce have a life span of 50 to 60 years.
  • Weed competition – grassy weeds present the greatest competition to established spruce, taking both nutrients and water. Use a glyphosate product to spray out grassy weeds around the tree, in an area extending several feet beyond the drip line.
  • Spacing competition – many old conifer shelterbelts were planted too close together – present recommendations are to plant them 12 feet between trees and 16 feet between rows. Try to thin out established spruce shelterbelts by removing dead, dying or weak trees.
  • Drought – Colorado spruce is much more drought hardy compared to white spruce. Any amount of water applied during drought years will be of an asset.
  • Shading – needles on lower branches will brown and drop off if shaded by overcrowded spruce or other trees.
  • Natural needle drop – Yellowing and browning of needles in the fall is a normal occurrence on spruce. Only the oldest needles, located closest to the trunk are affected.
  • Competition from other trees – Siberian elm and poplars are very competitive trees and should not be planted adjacent to spruce. A person could try root pruning between rows, don’t root prune too close to spruce. Only root prune one side per year.
  • Disease – cytospora canker is a common disease on older spruce. The disease results in sporadic branch die-back. Prune out infected branches, no fungicides registered for control of this disease.

It could be a variety of reasons such as:

  • Herbicide damage – Several herbicides can cause browning of spruce; one of the most damaging herbicides is dicamba.
  • Salinity – spruce has poor tolerance to saline soils, do not plant spruce in an area where salinity may be a problem.
  • High nitrogen – spruce will brown from high nitrogen levels. Do not plant on old barn sites or near livestock shelterbelts and do not apply high rates of nitrogen fertilizer to spruce. If you want to fertilize your spruce, use a fertilizer that is recommended for conifers.
  • Insects – the most common insects on young spruce are: Spruce Spider Mite, Yellow-headed Spruce Sawfly and Spruce Budworm.
  • Disease – the most common disease on young spruce is needle cast. This disease is common during years of high precipitation, high humidity and low temperature. Fungicides such as Bravo or sulphur can be used to prevent this disease.
  • Septic pump-out – do not plant spruce too close to a septic pump-out. Salts or other contaminates from the pump-out may kill the trees.
  • Moving – roots may be damaged during moving. Move trees when they are small and dormant, and use as large a tree spade as possible.
  • Natural needle drop – Yellowing and browning of needles in the fall is a normal occurrence on spruce. Only the oldest needles, located closest to the trunk are affected.
  • Trenching – roots may be damaged by trenching being conducted too close to the base of the tree. The roots of spruce will extend approximately 2/3 the height of the tree, try not to dig within that area.
  • Winter browning – is more common in younger vs. older spruce
  • Needles may appear slightly or distinctly yellow, brown or red-brown, depending on the severity of the damage.
  • This type of damage is most likely due to evaporation of moisture from the needles during warm or windy periods in the winter or early spring. The moisture loss (desiccation) cannot be replaced since the soil is still frozen and the roots are inactive.
  • Winter browning is generally more of a problem on younger pine and spruce.
  • Evergreens on exposed sites are at a higher risk of being effected. Pine tends to be more susceptible compared to spruce.
  • The brownish discoloration of the needles often occurs on the west and south sides, (south side due to sun reflection from snow, west side from prevailing winds).
  • Most winter browning damage occurs in early spring when the ground is still frozen and the temperature is above 0°C causing moisture loss of the needles. Damage from winter browning varies from year to year.
  • Reducing moisture stress during the growing season will reduce the likelihood of winter injury. To help lessen the damage, taper off and discontinue watering during the fall to allow for hardening off. Then water evergreens well just before freeze up and apply an anti-desiccant (available at garden centers) in late fall.
  • In some cases, severe needle loss may occur, but as long as the buds are not damaged, new needle growth may take place in the spring.
  • Watering and applying a light application of fertilizer, as soon as the ground thaws in the spring, will help the trees recover quicker. The homeowner should not be hasty in removing the affected trees until the full extent of the damage can be determined – winter browning, while unsightly, is not always fatal.
  • During the summer, following a period of hot, dry windy weather, evergreens (conifers) can exhibit browning, needle loss and/or dieback due to desiccation.
  • ​Winter browning or summer drought damage of conifers should not be confused with the normal shedding of needles in the fall which is called natural needle loss.
  • After conifer needles are two or three years old (depending on the species), they will turn brown and fall off. Natural needle loss will occur toward the center of the tree, while the new growth and previous year’s growth remains normal. Only the oldest needles, located closest to the trunk are affected.

This could be attributed to several causes:

  • Drought – poplars are water loving trees with a shallow, lateral spreading root system. During severe drought years, top die-back could occur.
  • Disease – there are several canker diseases that will kill the tops of poplar. There is no control for canker diseases other than removing and burning infected branches. The poplars that were distributed in the past from the Agroforestry Development Centre were resistant to most canker diseases.
  • Not hardy to the area – poplars are fast growing trees and some may be damaged by low temperature injury in early fall or late spring. This type of damage generally occurs on younger poplars (3-6 years of age). Poplars that were distributed from the Agroforestry Development Centre were proven to be cold hardy for most of the Prairies.
  • Age – poplars are fast growing, short lived trees. You will generally see top die-back after 20 to 25 years of age.
  • Borers – carpenterworm and poplar borer generally infest poplars that are weak and stressed. There is no registered pesticide for control of borers. Poplars that were distributed from the Agroforestry Development Centre were resistant to most borers.
  • If the temperature drops below freezing during the active growing season then trees may experience frost damage.
  • Some signs of frost damage are leaves that have turned black and fallen off.
  • Depending on the stage of growth the tree when temperatures dropped will determine the extent of the damage.
  • The most succulent growth will be the most negatively affected. This will be apparent on such species as green ash. Expect to see black tips and frozen leaves that will drop off.
  • Also, you may notice small spruce buds which have frozen and turned a pinkish/brown color. They may drop off as well but the overall health of the tree will not be affected.
  • The trees will likely recover whether they are mature or just newly planted. They may be slow in leafing out or in the case of newly planted trees they may not leaf out at all this year.
  • Therefore, keep this in mind when considering replacements for next year. It would be advisable not to remove the effected trees and wait until next spring to determine the extent of the damage.
  • Very few trees will perish. Frost should not cause any long term negative impacts and, therefore, there is no cause for alarm. To ensure the best survival after frost, keep affected trees as healthy and free of stress (weed competition) as possible.
  • Some wildlife grazing and damage can be expected in a wildlife planting. All species are potential food for some wildlife at some time of year.
  • Species such as dogwood, willow, and spreading shrubs will tolerate browsing.
  • There are products on the market which will help alleviate wildlife damage:
  1. Plastic wraps and tree guards will protect the stem and bark from rabbits, deer and mice.
  2. Topically applied commercial sprays can be used to deter wildlife browsing by making the tree ‘unpalatable’ for a brief duration.