Tomicus destruens

The Tomicus genus is composed of seven species of Coleoptera from the subfamily Scolytinae (Curculionidae).  They cause damage to species of the Pinus, Abies, Larix and Picea genus.  They are distributed throughout most of the Palearctic region since their first appearance in North America in the 1990s.

Tomicus destruens is considered an aggressive species that is widely distributed in masses of pine forest.  T. destruens attacks P. halepensis, P. pinaster, P. pinea and especially P. nigra.


MORPHOLOGY AND BIOLOGY

T. destruens can measure between 3.5 and 4.5 mm long.  It has a black head and thorax.  The elytrons and legs are brown.  Oviposition takes place in the maternal galleries, specifically in some incisions that the female makes on both sides of the gallery.  The eggs are white and about 0.5 mm diameter.

The number of eggs that the females lay can vary between 60 and more than 200.  The larva is apodous and curved.  It is white, but its head is brown.  When they are born they barely reach 1 mm in length, but in the 4th and final larval stage their length is equal to or slightly greater than that of the imagoes.

The pupa grows at the end of the larval galleries, inside the pupal chamber.  They are found on the bark or between the bark and the wood.  These pupae are whitish and already show the visible appendages of the imago.

T. destruens has two clearly different stages in its life: one under the bark of weak trees, where copulation, egg laying and complete growth of the new generation take place; and another in the branches of the crowns of healthy pine trees, where the imagoes feed on.

T. destruens starts flying from mid-September until the maximum temperature is below 20 OC.  This can also happen in short periods of time from December to February.  Between October and December, they lay the eggs of the first generation which emerge in March.

When the maximum temperatures in February or March rise above 20 OC, reproductive flight begins again, as well as, the egg laying of the second generation which emerges in May or at the beginning of June.  Both generations are siblings because they come from the same parental generation.

Reproduction begins after finding a host tree through the sense of smell (at long distance) and sight (at short distance).  Once located, the females begin to bore a hole in the tree trunks and thick branches.  The male enters after her and following copulation, stays behind the female removing the sawdust, whilst she excavates the vertical and uniramous gallery.  The female lays each egg individually, in small incisions on either side of the gallery.  She later blocks the holes to stop predators from getting to the eggs.

After a few days the larvae are born and begin to perforate galleries perpendicular to the maternal galleries, filling them with sawdust and excrement to stop predators from entering.  The larva goes through four stages of change, later becoming a pupa inside a small chamber under the bark of the tree, which can mark the wood.  The preimago, with no pigmentation, remains for some time in this chamber, to later leave by boring a hole in the bark.

Afterwards, it flies to the crowns of the trees and inserts itself into the pith of the dying branches, to feed and mature sexually. The imagoes remain in the crowns throughout the summer, moving from one branch to another.  The ends of the branches are often broken and fall to the ground.  The parental generation also needs to spend some time feeding on the branches, between egg laying in autumn and again in spring.


SYMPTOMS AND DAMAGES

The Tomicus genus produces two types of damage: subcortical galleries in the trunk and thick branches; and galleries in the small branches of the crowns.  The attack in the crowns is irrelevant, given that the trees they attack have enough strength to regenerate their losses.  Nonetheless, the attacks in the trunk are always deadly.  Through the maternal galleries and most of the larval galleries fungus is introduced, which deteriorates the phloem of the gallery perimeter.  Furthermore, whilst the larvae are feeding, a mechanical destruction is produced in the phloematic channels.

They go for trees or sections of trunk, with bark that is neither too thin nor too thick.  They do not tend to attack reforested trees. The trees that have been attacked are easily identified 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 that are in the initial stages of decline, mainly because of lack of water, competition with other trees and mechanical or fire damage.  Their behaviour is that of an aggressive species, capable of killing quite strong trees, but they do not tend to attack previously attacked trees by other bark beetles (except for very rare cases, such as P. pinaster that are attacked by Ips sexdentatus).

In the absence of occasional damages, such as fires or drought, the trees that are at most risk of attack are found in thin, poor soil with scarcely any rain and too many trees per ha.  Frequent attacks on very old trees (more than 80 years old) have also been detected, this is possibly linked to the trees aging.  Another risk factor is the forest work involved in clearing and extracting trees.  In some cases, attacks have been registered in healthy trees.

Special attention must be paid to the periods of intense and prolonged drought, as they influence Tomicus destruens attacking not only single trees, but also forests.  Between 1994 and 1996 around 40,000 ha of pine forest were affected after a prolonged drought in the Region of Murcia.

Abandoned wood from forest work is the perfect material for Tomicus destruens to reproduce and once the population density has reached high levels, it could become a real threat for other trees and forests. Regarding the pest situation, at first the dead trees appear to be alone or in small circular areas.  The pest populations grow rapidly and the outbreaks change into continuous stains, more spread out every time.

Visual diagnosis is based on the presence of volcanoes of yellow resin in the tree trunks and thick branches.  Normally this symptom is detected after the crown suddenly turns yellow.  By removing the bark, the presence of the species is confirmed.  This discolouration is produced in advanced stages of infestation, when the parent and part of the offspring generation have abandoned the host.

This makes controlling it more difficult, as the treatments for cutting down and debarking a tree are only partly effective, by working solely on the part of the offspring population and practically nothing on the parental generation.  In very weak or cut down trees no volcanoes of resin form, so diagnosis can only be carried out by debarking the trees and identifying the galleries.


SCALE OF DAMAGE

There are two types of damage, with different management methods.

EXTENSIVE DAMAGE in forests. The following levels of damage have been suggested:

Grade 0: Stand with some dead trees. It is possible to find rejected attacks.
Grade 1: Stand with dispersed dead trees.
Grade 2: Stand with dead trees and small dispersed circular areas.
Grade 3: Stand with clear evidence of large or many small circular areas tending to mass mortality.
Grade 4: Mass mortality.

LOCALISED DAMAGE in public areas, such as parks and gardens.

Grade 0: Some dead trees and possible rejected attacks in other trees.
Grade 1: Death of less than half of the trees.


DETECTION AND MONITORING

In forests 1 CROSSTRAP® MINI should be placed every 20 ha, separated at least 1000 m from each other. In surfaces less than 20 ha, at least one trap should be placed per stand or forest. The traps should be placed in areas with good visibility, such as forest borders, forest trails or fire-breaks. Windy areas should be avoided, as the wind complicates the insects’ flight and could damage the traps. A detection trap system should cover the environmental variability of the monitored forest.

As a rule, traps should be placed and active between mid-September and mid-April. These periods of time could be shorter in years with the beginning of autumn and spring being very warm.

For monitoring, wet captures are recommended as they allow for the precise identification of the captures.  For this purpose, fill the collection cups with 10 ml of diluted propylene glycol (10 to 20%), or with antifreeze for the car. This liquid is used for killing the captures as well as preserving them, as long as it does not dissolve too much with the rainwater, in which case it should be replaced. It is recommended to collect the captures at least every 15 days.


EXHAUSTIVE MONITORING

In forests

For exhaustive monitoring, the traps should be placed between 100 and 500 meters apart from each other in forest trails, fire-breaks or forest borders.

This means a density of 0.3 to 3 CROSSTRAP® MINI per ha. They can also be placed inside the forest, as long as it is not too dense. Dry captures are recommended for exhaustive monitoring using the slippery collection cup with a stainless-steel mesh on the base. The collection cup stops the bark beetles from escaping because they cannot climb out due to the slippery product, although it allows the entrance and exit of the predator Thanasimus formicarius, which devours the captured insects. In this way, the impact of the trap system is minimized on useful fauna.


In parks, gardens and residential areas

The management of Tomicus in parks and gardens presents some peculiarities that differentiate it from management in forest environments. The biggest risk of attack in ornamental trees is caused by mechanical damage. Work involving excavation around the trees more or less severe, destroys the roots and often causes a weakening that facilitates the attacks by Tomicus. In general, ornamental trees are not very vulnerable to attacks by Tomicus, provided that they maintain the same conditions that they grew in. Sometimes, placing or removing irrigation systems in garden areas can provoke attacks from these insects.

The control of Tomicus in these situations must be very effective, as it is about reducing the mortality rate of the trees to zero. Therefore, efforts should be made to intensify trapping to the maximum. This means a density of 3 CROSSTRAP®MINI per ha, should be controlled each week.


NECESSARY MATERIAL

CROSSTRAP® MINI traps and diffusers of kairomones ECONEX TOMICUS DESTRUENS 60 DAYS (Code: VA250) that will be hung on the trap using the holes made for this purpose in one of the PVC sheets.

ECONEX TOMICUS DESTRUENS 60 DAYS contains two diffusers of kairomonal attractant for males and females of Tomicus destruens + 2 hangers in the form of a clip to hang the diffusers on the trap.

Diffuser A contains 25 ml of a-Pinene with 98% purity. The release rate is 0.3 gr. per day at 20 OC.

Diffuser B contains 100 ml of ethanol with 96% purity. The release rate is 2 gr. per day at 20 OC.

The diffusers are in a blister pack and individually packaged in an aluminum sachet with label specifications. They last for 60 days in field conditions. Once removed from the packaging, the diffusers need no activation or opening, just placed correctly in the trap.

17,82 € (excl. VAT)

The CROSSTRAP® MINI is a state-of-the-art forest trap. This trap has been created through an R + D project (University of Murcia – ECONEX) aimed at developing traps and attractants for forest insects.

The trap consists of a 33 cm diameter polypropylene lid with a central carabiner attached to a steel spring. Two reinforced PVC vanes are held in place by four steel springs in the lid’s upper section. They are used as elements of dynamic suspension, serving as shock-absorbers against the force of the wind exerted on the trap, avoiding its breakage in the forest. They are also fixed in the lower part of a 30 cm diameter polypropylene funnel. The collection cup is fixed to the lower part of the funnel by screws.

The vanes, funnel and collection cup are treated with a slippery product that increases the amount of captures considerably, also preventing the insects from escaping.

The CROSSTRAP® MINI trap can last up to 7 years due to its structure and highly resistant components. The unfolded trap measures 33 cm diameter x 100 cm high. Once folded, it is 33 cm diameter x 40 cm high, making its transport easier.

48,27 € (excl. VAT) 48,27 € (excl. VAT)

The trap can be used with two types of collection cup: CROSSTRAP® WET COLLECTION CUP for wet captures (with liquid), and CROSSTRAP® DRY COLLECTION CUP for live captures (without liquid).

CROSSTRAP® WET COLLECTION CUP (Code: TA156) has an approximate capacity of 2 litres and a drain in the upper section to prevent it from filling with rainwater.  It measures 12.5 cm diameter x 19 cm high and contains a slippery product to prevent the captured insects from escaping.

CROSSTRAP® DRY COLLECTION CUP (Code: TA157) has the same capacity and measurements as the CROSSTRAP® WET COLLECTION CUP but it has a base made of stainless steel mesh that drains away the rainwater 100% and eases air circulation.

5,61 € (excl. VAT) 7,11 € (excl. VAT)

FACTORS THAT INFLUENCE THE NUMBER OF TRAPS NEEDED

In forest environments, the number of traps are determined by the area that needs to be covered, forest trails, fire-breaks and accessible borders. For exhaustive monitoring, a density of between 0.1 and 0.3 CROSSTRAP® MINI per ha is recommended, separated between 100 and 500 lineal metres. Therefore, it is recommended to use a GPS system during installation.

 

In parks, private gardens, play areas, public gardens or small forest areas (<5 ha), the density of traps increases greatly, even using up to 3 CROSSTRAP® MINI per ha.

In these areas, the death of just one tree is shocking enough to intensify trapping and to capture the greatest number of insects possible.


STORING THE DIFFUSERS

The product should not be stored for a long time. It must be stored in its original packaging and in the refrigerator at 4 OC; or in the freezer at -18 OC, in which case it will last between 90 and 150 days respectively.


PACKAGING

Corrugated cardboard box of 100 units (20 packs of 5 units).
Box size: 0.60×0.40×0.35 m (length x width x height).
Box weight: 23.5 kg.
No. of boxes per pallet: 20.
Pallet size: 1.20×0.80×1.90 m (length x width x height).
Pallet weight: 477 kg.

Tomicus repellent diffuser with 120 days duration.

Benzyl alcohol diffuser containing 100 ml of product. This product acts as a repellent for T. destruens, having shown a reduction in captures between 70 and 80 % in traps with T. destruens attractants and these diffusers, compared to the same traps without this repellent.

Its use is recommended for the protection of individual trees in situations of risk in parks, private gardens or public gardens, as well as singular and monumental trees.

6,24 € (excl. VAT)

To optimize its effectiveness, it is recommended to install a CROSSTRAP® MINI trap with the kairomonal attractants ECONEX TOMICUS DESTRUENS 60 DAYS near the trees that need to be protected.  A minimum distance of 20 m between the trees and the trap has to be maintained, in order to ensure the insects go to the trap and not to the protected trees.

A diffuser should be placed every 4 lineal meters of the trunk, until the bark becomes thinner. The diffusers will be placed by nailing them to knots or other areas of dead wood in the tree.


STORING THE DIFFUSERS

The diffusers must be stored in their original packaging and in the refrigerator at 4 OC; or in the freezer at -18 OC, in which case they will last for 2 and 4 years respectively.


PACKAGING

Corrugated cardboard box of 200 units (20 packs of 10 units).
Box size: 0.60×0.40×0.35 m (length x width x height).
Box weight: 17.5 kg.
No. of boxes per pallet: 20.
Pallet size: 1.20×0.80×1.90 m (length x width x height).
Pallet weight: 357 kg.


Recommended information:

ECONEX CATALOGUE OF PRODUCTS AND SERVICES FOR FOREST PESTS

Catalogue in PDF format with 94 pages. It is an essential reference book about the biological behaviors of the main forest insect populations. It also includes ECONEX solutions to satisfy the problems caused by these insects through the use of traps and specific attractants.

You can download the catalogue by clicking on the image.

ECONEX TOMICUS DESTRUENS 60 DAYS LEAFLET

Leaflet in PDF format that can be downloaded by clicking on the image

ECONEX WEB RESOURCES

Section of the ECONEX corporate website that allows you access to online information about ECONEX solutions for the biocontrol of other relevant agricultural and forest pests.

To access ECONEX WEB RESOURCES click on the image.