Infestation of pine trees in Javea and surroundingsBack
The pines in the Costa Blanca have had a lot to endure in the last year. In addition to the drought and pine processionary caterpillar, they are also affected by beetles such as Tomicus destruens that have caused many trees to be lost.
Now we also see that the pine trees in Javea and the surrounding area look brown and dehydrated at the top (photo 1),it is mainly the young needles that dry out as we can see in the picture below.
Commissioned by BIO JARDINSOSTENIBLE S.L.U. the entomologist Silvia Hellingman has examined over 50 samples from different locations to investigate what is happening with the coniferous trees.
In all samples and on the spot observations we have found several aphids and scale lice (Diaspididae) (Photo 2,3).
The insects feed on the juices of the needles. By sucking the juices the needles dry out, which gives a sad appearance to the trees.
The cause of the many and different pests is due to the climatic conditions. We are dealing with an exceptionally warm winter, as a result of which insects that usually overwinter as an egg become more active with all its consequences.
In addition to lice, also many egg packages from the pine processionary caterpillar were found, as well as the nests left by the young caterpillars to settle elsewhere in the trees (Photo 4). These spots are also brown coloured, this phenomenon in combination with the needles affected by the leaf and scales ensure that the pine trees look bad.
Fungi due to stress
Mildew spores were also found in some samples. If the trees are in poor condition due to, for example, periods of long drought, they become susceptible to fungi.
Fungi can be transmitted to the pine trees by numerous insects.
Bacteria Candidatus Phytoplasma pini
Recently there was an article in the local media about the damage to the coniferous trees in Javea in which the bacterium Candidatus Phytoplasma pini was named as causative.
It could be possible; bacteria on plants are often transmitted by insects by, for example, aphids, leaf fleas or cicadas.
The impairment as we saw, however, does not match the symptoms of the infection by the Candidatus bacterium.
In Spain, this phenomenon is called Escoba de brujas. (Picture 5).
It will have to be further investigated, but it is very unlikely that there is a bacterial infestation here, although due to the climate change, more and more plagues are manifesting which may or may not be transmitted by insects.
Nature reacts quickly
In all locations there are many larvae of various species Ichneumonidae (Syrphidae) present. These are natural enemies of the aphids and there are also species that focus on young pine processionary caterpillars.
The first larvae of ladybirds have been observed in various affected trees, these larvae feed on different types of leaf and fungus lice.
In addition, we found many parasitized leaf and scale lice. This is the work of the zealous parasitic wasps.
The parasitic wasps deposited their eggs in the aphids. The larvae eats the aphid from the inside out. On the attached photo we can see the exit holes of the parasitic wasps (Photo 6). The parasitic wasps have flown out of the dead louse. They mate and search for new aphids to parasitize them.
In addition to the beneficial insects, the insects that suppose a thread to the pine trees are eaten by many birds.
The dry and warm autumn and winter have ensured that the insects that would normally be in winter rest have affected the pine trees.
Fortunately, there are many natural enemies present that provide a significant reduction of the pests. Because of the current cold period, the pest pressure will naturally decrease.
We will continue to monitor the development of the damage in the pines and we will of course report new developments.
Research and photos: Silvia Hellingman
Text: BIO JARDINSOSTENIBLE S.L.U. / Silvia Hellingman