ECONEX TOMICUS DESTRUENS (60 days)

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ECONEX CATALOGUE OF PRODUCTS AND SERVICES FOR FOREST PESTS

Kairomone diffusers for the attraction of both sexes of the species Tomicus destruens, with a duration of 60 days in normal field conditions.

The diffusers are blister-pack shaped, with a polyolefin layer permeable to the active ingredients, and they are packaged in an aluminium sachet with labelled specifications. Once taken out of the sachet, the diffusers do not need any activation operation. Simply place them directly in the trap. DO NOT OPEN, CUT OR PERFORATE THE BLISTERS. The appropriate emission rate is achieved by diffusion through the polyolefin layer.

The Tomicus genus is composed of seven species of Coleoptera from the subfamily Scolytinae (Curculionidae) that cause damage in species of the Pinus, Abies, Larix and Picea genus. They are mainly distributed in the Palearctic region, having been introduced into North America in the 1990s.

The T. destruens species are widely distributed in pine forests. It attacks P. halepensis, P. pinaster, P. pinea and exceptionally P. nigra.

MORPHOLOGY AND BIOLOGY

T. destruens can measure between 3,5 and 4,5 mm long, they have a black head and thorax, the elytrons are chestnut brown, the same as the legs.  Oviposition takes place in the maternal galleries, in some incisions made by the female on both sides of the gallery.  The eggs are white and approximately 0,5 mm in diameter.

The number of eggs that the females lay can vary between 60 and more than 200.  The larvae are apodal, curved, and white in colour with a brown head.  When they are born they barely surpass 1 mm in length, reaching in the 4th and final larval stage the same length or slightly more than the imagoes.

The pupae live at the end of the larval galleries, inside the pupa chamber, situated in the bark or between the bark and the wood.  These pupae are whitish and you can see the appendages of the imagoes.

T. destruens has two clearly different stages in its life: one below the bark in debilitated trees, where copulation takes place, then egg laying and the complete development of a new generation.  The other stage develops in the branches on the tops of healthy pine trees, where the imagoes feed.

T. destruens starts to fly in the middle of September until the maximum temperature is less than 20⁰C, something that can also happen in short periods of time from December to February in which they can fly. Between October and December the first generation eggs are laid and hatch during March.

When the maximum temperatures in February and March begin to exceed 20⁰C again, reproduction starts a reproductive flight once more, laying the second generation eggs that will emerge in May or at most the beginning of June. Both generations are sisters, as they come from the same parental generation.

Reproduction starts after finding through the sense of smell (at long distance) and sight (at short distance) the host tree. Once located, the females begin to bore a hole in the bark of tree trunks and thick branches. The male enters in after her and after copulation, it stays behind the female clearing away the sawdust, while the female excavates the vertical and uniramous gallery.  The female places each egg individually, in small incisions on either side of the gallery, cementing the cavity afterwards to stop the egg predators from gaining access.

Shortly after, the larvae are born and begin perforating the galleries perpendicular to the maternal galleries. They fill them with sawdust and excrement behind them to stop predators from entering.  The larva goes through four stages, later transforming into a pupa inside a small chamber in the interior of the bark of the tree, which can mark the wood.  The pre-imago, without pigment, remains some time in this chamber to later come outside through one of the holes bored in the bark.

After this, they fly to the tree tops and insert themselves into the xylem of dying branches, to feed themselves and mature sexually. The imagoes remain in the tops of the trees throughout the summer, moving from one branch to another.  The ends of the branches are very often broken, falling to the floor. The parental generation also needs to spend time feeding itself on the branches between the egg laying in autumn and again in spring.

DETECTION AND MONITORING

In forests 1 CROSSTRAP^® MINI trap per 20 ha should be installed, the traps should be separated at least 1000 m from each other.  In surfaces less than 20 ha at least 1 trap should be installed per forest stand. The traps should be installed in areas with good visibility, such as edges of the forest, forest paths or fire-breaks.  Especially windy areas should be avoided, as it makes it difficult for the insects to fly and could damage the traps. Detection sampling should cover the environmental variability of the forest, the object of monitoring.

In general, traps should be installed and working between the middle of September and the middle of April. These cycles could be much shorter in years where the beginning of autumn and spring are very warm.

For monitoring it is recommended to choose wet captures, given that it will allow the precise identification of the captures. For this purpose, the collection cups can be filled with 10 ml of diluted propilenglicol at 10% or 20%, or anti-freeze for the car could be used.  This liquid is used for killing the captured insects as well as preserving them, as long as it does not get too diluted by the rain, in which case it should be replaced. As a minimum, it is recommended that captured insects be collected fortnightly.

EXHAUSTIVE MONITORING

In forests

To intensify monitoring, the traps should be placed at a distance of 100 and 500 metres apart, following forest trails, fire-breaks or the edges of the forest.

The amount of traps can rotate between 0,3 and 3 CROSSTRAP^® MINI traps per ha. They can also be installed inside the forest, provided that the forest is not too dense. For exhaustive monitoring dry (live) captures are recommended, using the collection cup with a stainless steel mesh and a slippery film.

This collection cup prevents the beetles from escaping, as they cannot climb up due to the slippery film. But, it allows the entrance and exit of the predator Thanasimus formicarius, which eats the captured insects. In this way, it minimizes the impact of trapping non-target species.

In parks, gardens and residential areas

The management of Tomicus destruens in parks and gardens presents some peculiarities that differentiate it from management in forests.  The biggest risk of attack on ornamental trees is the one induced by mechanical damages.

Work involving excavation around the trees destroy the roots, often causing a weakening that facilitates the attack by T. destruens. In general, the ornamental trees are not very susceptible to attacks by T. destruens, provided that they maintain the conditions in which they grew up in.  Sometimes putting or taking away irrigation in garden areas can provoke attacks by these insects.

Controlling T. destruens in these circumstances should be very effective, given that it is about reducing the mortality rate of trees to zero.  Therefore, efforts should be made to intensify trapping to the maximum, so that a density of 3 CROSSTRAP^® MINI traps per hectare can be used.  They should be controlled weekly.

NECESSARY MATERIAL

CROSSTRAP^® MINI traps and ECONEX TOMICUS DESTRUENS kairomone diffusers which will be hung on the trap using the holes made for this purpose in one of the PVC sheets.

SYMPTOMS AND DAMAGES

The Tomicus genus produces two types of damage: subcortical galleries in trunks and thick branches and galleries in the small branches on the crowns of the trees.  The attack on the crowns of the trees is irrelevant given that the trees that they attack have enough strength to regenerate the losses.  However, attacks on the tree trunk are always mortal, given that through the maternal galleries and especially the larval chambers the fungi gets in and produces the degradation of the phloem around the gallery.  Also, during larvae feeding, a mechanical destruction of the phloematic canals is produced.

They select trees or sections of tree trunk with bark that is not too thin nor too thick.  They do not tend to attack the reforestated trees.  The attacked trees are easy to identify because of the volcanoes of yellow resin that surround the entrance holes.  Sometimes, trees with rejected attacks can be found alive, but with volcanoes of resin.

They prefer to reproduce in trees with initial stages of deterioration, mainly due to lack of water, competition with other trees, damage by fire or mechanically damaged.  They behave like a primary species, capable of killing very weakened trees and they do not tend to damage previously attacked trees by other bark beetles (except in very rare cases in Pinus pinaster is attacked by Ips sexdentatus).

In the absence of episodic damages, such as fires or droughts, the trees at most risk of attack are the ones situated in poor, not very deep soil, little rain and too many trees per hectare.  Also, frequent attacks on very old trees have been detected (>; 80 years), which is possibly linked to ageing.  Another risk factor is forest work, such as thinning out the forest and extraction, given that in certain conditions, attacks have been registered in healthy trees.

Special attention must be paid to the periods of intense and prolonged drought, given that they are predisposed to attacks by Tomicus not only to individual trees, but also to large masses of forest.  Between 1994 and 1996 almost 40,000 ha of pine forest in the Region of Murcia (Spain) were affected, after a prolonged drought.

Wood abandoned in the forests from forestry work is the perfect material for reproduction and once its populations reach the highest levels, they can become a real threat for other trees and forests. 

When infested, at the beginning the dead trees appear isolated or in small stands.  The insect population increases rapidly and the focus changes into continuous stains, becoming more extensive every time.

The visual diagnosis is based on the presence of volcanoes of yellow resin on the trunks and thick branches.  Normally this symptom is detected after the crowns of the trees suddenly turn yellow.  After debarking the tree the presence of the specie is confirmed.  This discolouration is produced in the advanced stages of infestation, when the parents and part of the offspring generation have already abandoned the host.

This contributes to making it more difficult to control, given that treatments such as tree felling and debarking the tree are only partly effective, by acting solely on part of the offspring population and practically nothing on the parent generation.  In very weak or felled trees the volcanoes of resin are not formed, so diagnosis will only be carried out by debarking and gallery identification.

STORAGE OF THE DIFFUSERS

The diffusers must be kept in their original container and in a refrigerator at 4^oC, or in the freezer at -18^oC, in which case they will remain valid for 90 and 150 days respectively.