Pine caterpillar - Pytiokambi (Thaumetopoea pityocampa)
Pine caterpillar treatment
The pine caterpillar is one of the most important enemies of the pine tree. It is a nocturnal lepidopteran of the Thaumetopoeidae family. The larval stage of the insect consumes a large part of the leaf surface, with the result that it significantly limits the growth of young trees, while high infestations for consecutive years can lead to the drying out of young as well as old pines. The presence of the insect is noticeable in 1/3 of the pine forests, but the damage is mainly in areas where the trees are malnourished, the pine forest does not ‘regenerate’ (usually technical pine forests or urban groves) while the caterpillar’s natural enemies are also absent.
A characteristic of the larva is the allergic reactions it causes to anyone who approaches them, as as soon as they are threatened, they scatter hairs with toxins in the air that irritate the skin, eyes and respiratory system.
The adults appear from the end of July until October with a maximum flight in August, they live only a few days and in this short time they mate and lay eggs in the pine needles. Each female lays more than 300 eggs, usually in clusters of more than 70 eggs inside silk sheaths. Young larvae emerge 30-45 days later and feed at night on pine needles while hiding in their nest during the day. They consume a large amount of pine needles and this can be particularly stressful for young pines. As soon as they grow in size they begin to weave a cocoon and protect themselves inside it from weather conditions and natural enemies.
Larvae complete five larval stages by early spring and then rush to find a suitable pupation site in the ground. The formation of a line (litany) is characteristic with the bodies of the larvae following each other trying to maintain contact. The group is always led by a female person.
They pupate within the soil, usually in light, sunny and loose soil, at a depth of 5-20 cm within silkworms. Pupation can last 4-5 months, while an extension of this is also observed for some part of the population for more than 2 years. July and August the first adults appear again.
Chemical methods of controlling the insect are now outdated and dangerous for the environment and humans in general, but also for the rich fauna of the pine forests in particular.
Biological control no longer lacks the effectiveness of chemical control, on the contrary there are several publications that support the opposite, even taking into account the neutral effect of the method on the ecosystem. It is worth emphasizing that biological control methods are perfectly compatible with all natural enemies such as predatory insects and parasitoids, birds, rodents, etc.
Bacillus thuringiensis (to combat newly hatched larvae)
Thuringia bacillus is the most widely used biological method of pine caterpillar control. It can also be used for aerial spraying by aircraft, while the other biological means present difficulties for this type of application. The entire crown of the pine tree is sprayed late at dusk so that when the young larvae come out at night to feed, they will ingest the bacillus toxin and eventually die.
Advantages: ease of application, high efficiency that can exceed 90% in newly hatched larvae.
Disadvantages: requires precise timing so applications are made when more than 90% of eggs have hatched. Earlier or later applications have low effectiveness. The developed larvae escape its action.
Steinernema feltiae (to combat all mobile stages)
Entopathogenic nematodes enter the motile stages as well as the pupa, release symbiotic bacteria and kill the target insects. Especially effective method if combined with the moisturizer.
There are the following application methods which can also be combined:
a) application throughout the county against all larval stages (requires a sufficient dose of formulation but has reduced labor for application).
b) targeted application inside the nest with a special telescopic rod (high efficiency, economy of formulation, increased application labor). Large larvae that have escaped the action of the bacillus may be killed.
c) application to the soil or directly to the larvae when they migrate to the pupation sites (economy of formulation, moderate application labor, great ease and high efficiency). The results of the application to the ground will be seen the following year as they do reduce the population, but after damage has been caused to the foliage.
Advantages: entomopathogenic nematodes can be turned against motile stages that, due to their size, have escaped the action of the bacillus. The method can be applied in combination with bacillus and give excellent results against all sizes of the insect, while on its own in combination with a moisturizing agent it can be a reliable solution when other methods have not been effective.
Disadvantages: cost of application, thoroughness and increased labor, inability to cover large areas (forests).
Bat nests (to contain adults)
They are wooden structures that are suspended from the pines and are colonized by the bats that already exist in the area. Due to their specialized configuration, the bats locate them very easily with the ultrasound system, while they are properly designed to protect them and the young individuals from natural enemies.
Bats are excellent predators of nocturnal insects and, of course, caterpillars. They consume huge amounts of food and are particularly effective against other enemies such as Lymantria. By colonizing the area (in the nest) the bats provide important protection over a large area as the moths that will attempt flight to lay eggs in the pine forest often fall prey to the bats. Efficacy is high and has a recognized research base that has been published in peer-reviewed journals.
Advantages: the method can be directed against adults so it can significantly reduce the problem before the adults can mate and spawn causing damage. Bats, unlike pheromone traps, can also limit the number of females that will basically create the problem.
Disadvantages: the method cannot deal with an overt larval infestation, so the effect is only seen in the future.
Pheromone traps (to mark and contain adults)
They are placed to mark the period of the first flights and the maximum flights and therefore the laying of eggs. This marking helps so that by counting the days we can predict when the majority of the eggs will hatch in order to apply one of the control methods described above. The method is worth it for the tagging rather than the mass trapping it promises.
Pros: Moderate reliability but sufficient for marking
Disadvantages: not enough for fighting, only males are caught
Light traps (to combat adults)
According to publications about 15 times more adults are caught than with pheromone traps. Also, people of both sexes are arrested.
Pros: Highly effective at killing adults of both sexes.
Disadvantages: cannot be applied where there is no electric supply. There is no selectivity and beneficial nocturnal predators may also be trapped.
The combination of the above methods in the light of an integrated plan to control pitioca can give excellent results.
Pine caterpillar treatment
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