Green Clinic field note
Why do the needles fall off, wither, and why do resinous secretions appear on the bark of pine trees?
Pine is an evergreen tree, which is a real decoration of forests, parks, gardens, homestead areas. This plant has natural healing properties and is often used in landscaping and landscape design, however, in the process of caring for pine trees, various unpredictable situations can occur, when the needles fall off, and you can also see cracks, wounds or resin leaks on the surface of the trunk.
One of the most dangerous diseases that can affect pine trees is the pine trunk nematode. What it is, what insects carry the disease, how to notice the first signs of the disease on the surface of the tree – about all this let us tell you in our article.
What is a pine trunk nematode?
The pine trunk nematode is a round worm that parasitises the wood of the pine tree, causing it to dry out. If preventive measures are not taken in time, the plant will subsequently lose its beauty or die. Nematodes live in the pine wood, feeding on its cells and also carrying fungi that contribute to the decay of the wood. Bark beetles that gnaw on the bark or trunk of pine trees carry the nematodes in their bodies or intestines. It is possible to transmit the nematode without even knowing it, because timber, sawn wood, sawdust, wood chips, and seedlings of various coniferous tree species can be infected with the nematode.
Next, we will consider which insects most often carry nematodes.
Which insects most often carry nematodes?
The main carriers of nematodes are bark beetles belonging to the family Curculionidae. These beetles have a long proboscis with which they pierce the bark of pine trees and lay their eggs in the wood. The beetle larvae eat away at the passages in the wood through which the nematodes move.The adult beetles fly out of the tree and fly to pine trees or other conifers growing in your park, garden or backyard, carrying nematodes on their proboscis, legs or in their gut. Bark beetles are most active in warm and humid weather, when the pine tree releases more sap. Among the most common species of bark beetles that can transmit nematodes are the following: pine bark beetle (Pissodes pini), pine longhorn beetle (Hylobius abietis), pine shorthorn beetle (Pachylobius picivorus), pine roundworm (Orchestes fagi).
It is worth noting that the needles shed and wither especially intensively if the pine tree has a moisture deficit, under such conditions the branches affected by the nematode dry out, and fallen needles can be seen on the ground near the trunk.
How can I spot the first signs of pine needle beetle on the surface of a tree?
Signs of pine stem nematode damage can vary depending on the tree species, degree of infestation, climatic conditions and time of year.
The first signs of the disease on the tree surface may not be very noticeable, but will become more pronounced over time. They include:
– Discoloration of the needles from green to yellow, brown or red. This indicates a violation of photosynthesis and interruption of the flow of water and nutrients from the roots to the crown.
– Falling needles from the tree. Needles can fall off both in single needles and in whole bunches. The needle drop starts from the lower branches and gradually rises upwards.
– Cracks, wounds or resinous discharge on the bark or trunk of the pine tree. This indicates damage to the wood by nematodes, fungi or beetles. Resin flows from cracks on the surface of the trunk as a defence reaction of the tree, but this reaction is not always effective. The resinous discharge can be clear, yellow, brown or black. Resin usually flows from cracks and wounds.
– Bending, twisting or distortion of pine shoots or branches. This indicates a violation of the growth and development of the tree under the influence of nematodes.
– The appearance of bubbles, blisters or growths on the needles, shoots or trunk of the pine tree.
– Wilting, yellowing, falling and loss of needles, starting from the top of the tree and gradually spreading down the trunk and branches. The needles can change colour from light green to yellow, red, brown or black. The needles can fall off in whole or in parts, leaving bare shoots.
If you notice at least one of the signs mentioned above, such as resin flowing down the tree trunk, needles falling off, or fallen needles on the ground near the tree, you should take preventive measures to help the plant fight the disease more effectively.
The specialists of the Green Clinic Ecosystem Phytopathology Centre apply the most modern, innovative approaches to conservation and longevity in their practice, because our mission is sustainable environmental development, plant and human health, their life, success, and well-being in harmony with nature.
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