Sometimes conifer trees will be looking green and healthy and then the next thing you know the needles are changing color. The previously healthy tree is now draped in discolored, brown conifer needles. Why are the needles turning color? Can anything be done to treat browning conifer needles?
There are numerous reasons for discolored needles. Needles turning color may be the result of environmental conditions, disease or insects.
A common culprit is winter drying. Conifers transpire through their needles during the winter, which results in water loss. Usually, it’s nothing the tree can’t handle, but sometimes during the late winter to early spring when the root system is still frozen, warm, dry winds exacerbate water loss. This results in needles that are changing color.
Normally, when winter damage is to blame for discolored needles, the base of the needles and some other needles will remain green. In this case, the damage is generally minor and the tree will recover and push out new growth. Less often, the damage is severe and branch tips or entire branches may be lost.
In the future, to prevent browning conifer needles due to winter drying, choose trees that are hardy to your area, plant in well-draining soil and in an area protected from winds. Be sure to water young trees regularly in the fall and winter when the soil is not frozen. Also, mulch around the conifers to prevent deep freezing, making sure to keep the mulch about 6 inches (15 cm.) away from the trunk of the tree.
In some cases, conifers changing color in autumn is normal as they shed older needles in place of new.
Another reason for brown conifer needles may be the fungal disease Rhizosphaera kalkhoffii, also called Rhizosphaera needlecast. It affects spruce trees growing outside their native region and starts on the inner and lower growth. Needlecast is most common on Colorado blue spruce, but it does infect all spruces.
Needles at the tips of the tree remain green while older needles near the trunk become discolored. As the disease progresses, the infected needles turn brown to purple and progress up through the tree. The discolored needles fall of in the middle of summer, leaving the tree looking barren and thin.
As with other fungal diseases, cultural practices can prevent the disease. Water only at the base of the tree and avoid getting the needles wet. Apply a 3-inch (7.5 cm.) layer of mulch around the base of the tree. Severe infections can be treated with a fungicide. Spray the tree in the spring and then repeat 14-21 days later. A third treatment may be necessary if the infection is severe.
Another fungal disease, Lirula needle blight, is most prevalent in white spruce. There are no effective fungicide controls for this disease. To manage it, remove infected trees, sanitize tools, control weeds and plant trees with adequate spacing to allow for good air circulation.
Spruce needle rust is another fungal disease which, as its name suggests, afflicts only spruce trees. The tips of the branches turn yellow and, in late summer, light orange to white projections appear on infected needles that release powdery orange spores. Infected needles drop in early fall. Prune diseased shoots in late spring, remove severely infected trees and treat with a fungicide according to the manufacturer’s instructions.
Insects may also be causing needles to turn colors. Pine needle scale (Chionaspis pinifoliae) feeding causes needles to yellow and then brown. Severely infested trees have few needles and branch dieback, and may eventually die entirely.
Biological control of scale involves the use of the twice-stabbed lady beetle or parasitic wasps. While these can control the scale infestation, these beneficial predators are often killed off by other pesticides. The use of horticultural oil sprays in conjunction with insecticidal soap or insecticides is an effective control.
The best method to eradicate the scale is the use of crawler sprays that need to be sprayed two to three times at 7-day intervals beginning in mid-spring and mid-summer. Systemic insecticides are also effective and should be sprayed in June and again in August.
The spruce spider mite is detrimental to the health of conifers. Infestations of spider mites result in yellow to reddish-brown needles, accompanied by silk found between the needles. These pests are cool weather pests and are most common in the spring and fall. A miticide is recommended to treat the infestation. Spray in the early to mid-May and again in early September according to the manufacturer’s instructions.
Lastly, mountain pine beetles may be the cause of discolored needles. These beetles lay their eggs under the bark layer and in doing so leave behind a fungus that affects the tree’s ability to uptake water and nutrients. At first, the tree remains green but within a few weeks, the tree is dying and in a year all the needles will be red.
This insect has decimated great stands of pine trees and is a serious threat to forests. In forest management, both spraying of pesticides and cutting and burning of trees have been used to try and control the spread of the pine beetle.
Emerald green needles with a hint of lime or leafy green needles coated in icy blue— cedar trees show off their evergreen glow in such beautifully distinct ways.
But one thing’s for sure: brown, yellow or orange cedar tree needles aren’t so pretty, and they bring up a whole lot of questions about the health of your tree.
If your cedar tree’s not living up to its “evergreen” name, keep reading to find out why.
To pinpoint how to fix your evergreen trees’ brown needles, let’s look at a few reasons why it shifted color.
Problem: Winter elements are notoriously tough on trees, but evergreens are especially vulnerable. Roots rely on water stored in tree needles once the ground freezes. This can drain the tree’s water stash quickly, causing the needles to turn brown from dryness.
Solution: If the tree is just suffering from dehydration, a protective spray for evergreens is a quick and effective fix. More info on this below.
Problem: Take the already dry winter and add in the beating sun—now your tree has even thirstier needles. Known as sunscald, needles in the direct sunlight turn uniformly brown because of the extra water loss. You may also see dead or dried areas of bark.
Solution: You can try an anti-desiccant spray to help with the dryness. We’ve got all the details below. As for the sunscald, wrap your trees’ bark in burlap to keep them warm and protect them from the winter elements.
Problem: Evergreens attract a few common pests and diseases, like the pine beetle or cytospora canker disease. Browning needles can be a symptom of infection, along with small holes, sawdust or large cankers leaking white sap on branches.
An anti-desiccant is a waxy coating sprayed on plants to shield them from moisture loss. Applying the film in winter is said to safeguard trees until spring.
For best results, we like to wait until the temperature drops to 40-50 degrees F. It's important to check that there’s no rain in the forecast for at least 24 hours. Using the anti-desiccant in the right elements at the right time is essential to avoiding tree damage.
Our technicians do one or two rounds of spraying the formula on dry needles in winter to help plants reduce moisture lose. Usually, these happen anytime between November and February, but your arborist will talk to you about what's right for your tree. Then, your tree will be good to go for the season!
Coniferous trees such as pines, spruces, firs, and cedars normally shed needles in the fall. The older, inner needles turn yellow then straw-colored to brown and drop from the tree. Depending on the tree species, the foliage on a given branch may thin progressively over one to three years. For example, spruce and fir needles also turn yellow and drop with age, but retain their needles for several years.
On white pines, a more dramatic yellowing of older needles is observed. By next month, only one year's needles may remain attached to the tree. Austrian and scots pines usually retain their needles for three years. Some needles turn brown rather than yellow as they age such as those of arborvitae and cedars. Adverse conditions in the preceding summer or winter may lead to an earlier or more pronounced needle drop in the fall.
In conifers, nutrient deficiencies can also lead to general yellowing and premature senescence of needles. Analysis of plant tissues is often needed to obtain an accurate diagnosis of the problem.
This article originally appeared in the October 8, 1999 issue, p. 125.
Arborvitaes turn brown for a handful of reasons, both natural and induced by disease, winter burn, and pests. It is essential to determine if the browning is natural or a symptom of a larger problem to prevent reoccurrence.
A natural cause of browning is seasonal needle drop.
Thuja trees are conifers, meaning they don’t drop their foliage every year like deciduous trees, and they don’t lose needles every year like evergreens. Instead, they shed their “leaves” every few years as a natural part of their life cycle. An entire branchlet on the tree turns brown as it ages and may remain on the tree for some time before dropping.
How can seasonal needle drop be prevented?
Seasonal needle drop from a tree cannot be prevented since it is a normal and natural process. Follow the best cultural practices to keep your arborvitae trees healthy, and the needle drop will be reasonable and restricted to old-growth instead of new growth.
While arborvitaes are known and revered for being easy-to-care-for trees, they are susceptible to several fungal problems that can result in your arborvitae turning brown.
How can diseases be prevented?
The best way to prevent fungal diseases is by keeping your thuja tree in good health through proper care. Unhealthy, stressed trees are more susceptible to disease problems.
If you observe your arborvitae turning brown during the winter or early spring, the cause is likely winter burn. A combination of freezing temperature, dry winter winds, sun, and a lack of water in the soil causes arborvitae foliage to turn brown because it is drying out. Symptoms typically appear at the tips of the branches and progress inward towards the center trunk.
How can winter burn be prevented?
Winter burn is preventable by protecting trees from the wind, minimizing water loss, improving the root system, and fertilizing appropriately.
The last cause of browning is problematic pests. Although thuja trees have fewer pest problems than other landscape trees and garden plants, a couple may cause damage.
How can pest damage be prevented?
Regularly inspect your plants and garden for pests, treating the insect problems quickly. You can also incorporate the following tips to help prevent pest damage.