Pine Tree Dying From Bottom Up

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Needle yellowing caused by aphid infestation Every year, we see ailing and dying conifers in our gardens and parks. This phenomenon can have various causes, one of which is animal pests, mainly needle lice. There are several types of aphids that threaten our conifers to a greater or lesser extent.

Spruce tubular aphid (Sitka spruce aphid)

Due to the mild and dry winters of the last years, especially the spruce tube aphid or Sitka spruce aphid (Elatobium abietinum) has proliferated and caused considerable damage. The spruce aphid lives exclusively on spruces (main host), a change to other coniferous or deciduous species does not take place.

Host plants

Blue spruce (Picea pungens), Sitka spruce (Picea sitchensis, hence the name Sitka spruce aphid) and Omorica spruce (Picea omorika) are preferentially infested. Less susceptible is the native red spruce (Picea abies).

Damage pattern

The aphids colonize the trees from the inside to the outside and from the bottom to the top. The intensity of infestation depends on the climatic conditions of the location, i.e. they occur more frequently especially in warm, sheltered urban areas. Due to its sucking activity, the spruce tube aphid causes yellow spots and edges on the old needles. Later, the needles turn brown and fall off. The needles are damaged not so much by sap extraction as by the saliva that the aphids release when they prick them. Just a few punctures are enough to cause the needles to die. As a result, entire branches become stunted, and only the new shoots remain healthy. Other much larger aphids on conifers, e.g. the pine aphid, do not cause such damage.

Biology

The spruce tube aphid is the only green conifer aphid found on spruce and is not to be confused with other aphids living on conifers. It is 1.0 to 1.8 mm in size and can be identified with a magnifying glass by two red button eyes and two “stalks” on the abdomen called siphons. Depending on climatic conditions, the animals overwinter mostly as old lice, only in harsh locations also in the egg stage. At low temperatures below -15 °C the aphids freeze, so that no mass reproduction is to be expected in the following spring. Live larvae are released from the old lice. Reproduction may continue even at temperatures around 0 °C. Especially after mild winter weather, therefore, there is usually above-average mass reproduction in spring, but this largely collapses in June/July. This decline in infestation is due to seasonal chemical changes in the plant sap. Similarly, it is a matter of the composition of the plant sap that the May shoots cannot be colonized until late summer. From May, winged aphids also appear, which then fly to their summer hosts (various grass species).

Timely detection of damage

The cause of damage is usually detected too late. When the needles change color and fall off, the aphids are no longer present and the trees have lost their ornamental value, because fallen needles no longer grow back. The lack of assimilation area can result in growth inhibition and, in the worst case, tree death. For these reasons, it is advisable to carefully inspect endangered trees in early spring until the beginning of June, so that targeted measures can then be taken in good time. To detect an infestation, tap a branch inside the crown in March/April on a white DIN A4 sheet and catch the falling material. If there are more than 6 aphids per leaf, control is recommended. Juvenile aphids (spring) remain relatively firmly attached to the needle tissue with their sucking mouthparts, so that they are not always adequately captured by the tapping test.

Natural enemies

The spruce tube aphid also has some enemies, such as ladybugs, lacewing larvae, hoverflies, and spiders, which eagerly prey on them. However, they are often unable to stop a mass reproduction. Ladybug laying eggs Lacewing fly Lacewing larva sucking out aphid

Spruce gall aphids

Other pin aphids whose infestations are very conspicuous are spruce gall aphids; they cause considerable damage to spruce trees by twig deformation and shoot browning.

Host plants

Red spruce (Picea abies) is particularly frequently colonized, but also blue spruce (P. pungens ‘Glauca’), Sitka spruce (P. sitchensis) and, less frequently, Engelmann spruce (P. engelmannii).

Damage pattern

Zoom image available So-called pineapple gall formed by the green spruce gall aphid at the shoot base The sucking activity of spruce gall aphids disturbs the growth of conifers. This results in yellowing, curling or dropping of the needles. Strikingly large-scaled, pineapple-shaped growths form at the base of the shoots. The hazelnut- to walnut-sized galls are initially dark green and later turn brown and lignify. Shoots often kink above the infested areas and die.

Biology

There are two groups of spruce gall aphids with regard to their reproduction:

One is the group that forms winged migratory generations and requires a change of host to reproduce. These include the red and green spruce gall aphids, which colonize spruce as their main host and European larch (Laris decidua) as a secondary host.
The second group includes the yellow spruce gall aphid, which produces unwinged generations and also colonizes the above-mentioned plants.

The anthracite- to black-colored larvae of the spruce gall aphid overwinter at the base of a terminal bud. In early spring, the growing mother louse secretes white wax wool, under the protection of which a large number (100 to 150 eggs per animal) of eggs are laid around the end of April to mid-May. The infestation is clearly visible to the naked eye due to the white, cotton-wool-like wax piles on the terminal shoots. The strong sucking activity of the adult aphids and their offspring stimulates the young tissue of the spruce buds to form growths. The above-mentioned chambered galls are formed, in which numerous young aphids develop. May shoots continue to grow more or less, depending on the type of gall aphids, on the tip. Pineapple galls at the shoot base Pineapple galls with the brood chambers Woody pineapple gall after the aphids leave In July/August, the chambers open and release the aphids. With the exception of the non-host-changing species (= yellow spruce gall aphid), they fly to the European larch (Larix decidua), which is therefore also referred to as the “secondary host”, and continue their further development here. The Japanese larch (Larix japonica) is not infested. The needles of infested larches curl and discolor, usually leading to premature needle drop. In early summer of the following year, the aphids return to the spruce and the cycle begins again. Unlike the green spruce gall aphid, the red spruce gall aphid has much smaller (cherry pit to hazelnut-sized) greenish-yellow, terminal strawberry-shaped galls. No galling, but budding of buds for the next year. No galls, but budding of a new cone

Countermeasures

An environmentally friendly method of control would be regular collection of the still closed green galls, which largely reduces progression of the infestation. However, this control method is very costly and can only be carried out in gardens and parks on individual trees that are not too tall. If chemical control is indeed necessary, the right time must be chosen. In this case, treatment must be carried out before egg-laying begins and before increased wax shedding by the mother aphids. Due to the wax wool, the animals are well protected from the spraying agent. Also, too low and too high temperatures impair the effectiveness of the agents.

Other aphids on conifers

Needle lice occur not only on spruce, but also on fir, pine, Douglas fir and, as already mentioned, larch. The needle lice colonize young shoots, twigs and needles. The needles turn yellow and curl. The young shoots tend, cripple and die. Depending on the species, the aphids excrete white, woolly wax filaments or are dark, variously sized viviparous animals with honeydew formation. Black sooty fungi settle on the sticky excretions of the aphids, which are not harmful to the plant itself, but which significantly reduce the ornamental value of the trees.

Arguments against capping:

1. the tree becomes hollow

The tree rots from the interfaces into the trunk. This causes the trunk to become hollow. The outer annual rings of the trees usually cope with such injuries. First of all, the older annual rings die at the cut. These are not quite so important for the vitality of many tree species. The tree slowly hollows out starting from this point. Gradually, as the load-bearing residual wall thickness (outer growth rings) becomes thinner, the tree’s stability and the breaking strength of the branches suffer. Then a hollow tree becomes a static problem (traffic safety). The life span is shortened. However, we humans often find it difficult to register this. How can we, if the consequences will only be felt in 10, 20 or 50 years and the tree will only live for 50 years instead of 100.

2. branch connection of new shoots is poor

Newly sprouting branches have a poor connection. They do not grow starting from the center, the trunk center, and are not interlocked with the growth rings, but grow from the outer trunk layers. The new shoots become thicker, longer and heavier from year to year and successively become acutely prone to breakage due to the poor connection. Only original primary branches that have grown from buds of one-year-old branches (the trunk was also once a one-year-old branch) over the years are well “interlocked” and usually very stable (there are exceptions). This is no longer the case for all new shoots from the time of capping. Therefore, primary branches should not be cut off without good reason. Therefore, it is best to avoid capping if at all possible.

Consequences of crosscutting

Capping also has consequences in terms of future maintenance requirements. Due to the poor branch attachment to the trunk head described above, it is necessary to maintain and prune the crown every two to five years. For safety reasons (danger of breakout), increased tree inspections are necessary, from which the necessary pruning measures are derived. This higher control and care expenditure arising in the future is therefore connected in most cases with higher follow-up costs. However, costs can only be seriously assessed if they are calculated on the basis of a specific case. Even trees that have been optimally pruned cannot do without inspection and maintenance.

Considerations

Are we allowed to cut trees?

In the end, it is up to us how we evaluate what the picture shows. Does every tree that we plant artificially somewhere have the right to grow old as unmolested as possible? Or do we, as the “creators” of the tree, have the right to deface or shape it – even at the expense of the tree’s lifetime? At this point, the discussion already becomes philosophical and difficult.

Are trees disfigured by pollarding?

I maintain that learned arborists would answer “yes” to this in the majority – me too. Some allotment gardeners, laymen or property owners have been shown to disagree. Perhaps they are not enlightened and are starting from misconceptions. But there are also enlightened laymen and even some experts who see a design value, perhaps even an art form, in capping. It may be that there is no value placed on the trees growing old. Practice shows that many people do not mind the appearance of these artificial tree forms at all, that they even find them beautiful. Where money is not an issue, higher follow-up costs due to increased control and maintenance efforts should not bother either.

Are topped trees safer?

If topped trees are not regularly maintained, they will quite quickly become problem trees with reduced traffic safety. At least with regular maintenance and trimming of branches, you don’t have the problem of heavy branches breaking off and falling onto the playground, possibly injuring or even killing people. However, from a professional point of view, it can be said that this can be ensured without such mutilations with proper maintenance.

For your green future!

Are you interested in a career change, are you an arborist or are you on your way to becoming one? Or do you have a company and are looking for new people to strengthen your team? We have something for you: the arboriculture portal job exchange. This is where people meet to redesign their professional future. Still questions? Then contact us directly. We would be happy to help shape your future!

Clear view through tree topping?

A clear view is certainly a value. But who evaluates the value of a free view and the value of a tree with a natural crown?

Is it possible to reduce leaf mass or fallen leaves by capping?

Often tree owners are bothered by the mess and work that falling leaves cause. However, capping does not solve the problem. That’s because trees sprout vigorously again in the spring after capping measures have been taken after leaves have fallen – they literally explode. New shoots stand close together and form a dense mass of leaves. And even in the first year after capping, large masses of foliage are therefore produced again, which continue to increase over the years.

Preventing tree felling with capping?

It is also possible that the client and the contractor have consciously accepted the disadvantages and done the best possible from their point of view. For perhaps the debate was to cut down the trees. Reasons for this could be that one does not want to have “dangerous”, large trees on playgrounds. Therefore, it could be that the capping of the trees was the compromise to leave the trees standing for a few more years, maybe decades, and for this reason they are deliberately maintained as a “hedge”.

Was the capping done professionally?

As questionable as capping is, and as easy as it is supposed to be to do, there is a “right” and “wrong” to capping. The pyramidal shape of the crown in the picture indicates that “professionals” did the cutting. The lower, older branches were left longer. This is good at first, because it encourages sprouting at the bottom. In fact, the lower branches need to be longer and stronger if they are to have the same vigor as the upper ones. But maybe it was just the intuition of a layman. Whether or not the shoot vigor in the present case is evenly distributed throughout the crown by the selection of the branches, will be shown by the budding. If the shoot length and quantity is the same at the bottom as at the top, you have struck the balance. In your case, however, I would guess that the top is sprouting more than the bottom.

Is capping tree destruction?

Beyond the sense and nonsense of this pruning, the trees definitely have potential to become a court case. But that would require a plaintiff, preferably a tree appraiser. If you are the owner of these trees, have not been informed about the problems of this type of pruning and do not agree with the “emergency measure”, you have a good chance to be successful with a claim for damages against the executing company. However, you will need to discuss this with an attorney and tree appraiser.

Contact tree appraiser if you have legal questions

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Anna Hein

Pine Tree Dying From Bottom Up