Dear Andras-

Some wood boring beetles can be successfully mass-trapped using pheromone or kairomone lures. The following website has a commercially available lure for X. dispar:

https://www.contech-inc.com/products/industrial-products/agriculture/item/orchard-insect-management-3

Generally these lures are placed on Lindgren-type funnel traps. Be sure to remove the infested materials and place the traps rather far away from your trees, as 'spillover' (unintended infestation) can occur if traps are too close to healthy trees. The lures would best be deployed during the phenological timing of the beetle that matches the spring flight (March through April or May), so as to capture all newly emerging adults and break the infestation cycle. The beetle has only one generation per year but is capable of re-infesting the same trees for several years and building up large populations.

Another option would be to apply a solution of entomopathogenic fungal spores to the surface of your healthy trees, such as Beuvaria bassiana, which can also be commercially obtained.

Are you certain the beetle you have is not Ips typographus? The two species are similar in appearance. Xyleborus dispar generally colonizes Angiosperms, with infestation looking like 'shot holes'. Ips typgraphus attacks the bole and will leave 'pitch tubes'.

Dear Thomas,

Thanks for your comment and help. I examined the insects and they are – as you wrote – Ips typographus. The situation is much worse than I have thought earlier because I. typographus may have 2-3 generations and they are baited by pheromones and the odour of the spruce holes. Bauveria bassiana may help but the time of its action matters. I will try it!

Baited traps may help too, but I am not sure whether they are available here?

Thanks again for your help.

Dear András,

once infested by the European spruce bark beetle, a Norway spruce normally dies. However, you might have a chance to save the six remaining trees by immediately felling and debarking the infested trees. I must agree that this measure does not guarantee the survival of the six remaining trees but the contrary (no measure) strongly enhances the infestation risk on the remaining trees.

Lures for Ips typographus can be commercially purchased in Europe, though the lures and traps are not cheap. A web search should turn up the products.

Insecticides are used as drenching preventive sprays on the trunks and larger branches. These insecticides need to be applied prior to adult beetle infestation. (Remember that overwintering beetles begin emerging in spring as soon as daytime temperatures consistently reach 50 F to 60 F.) However, timing can be difficult to determine since ips beetles can have multiple, overlapping generations and life cycles. Adults have been observed entering trees during warm days as early as late-February on through November. Because of this extended activity, two treatments (early spring and summer) may be needed to protect trees during high-risk conditions.

Insecticides used to prevent ips include either permethrin, bifenthrin, or carbaryl (Sevin) as the active ingredient. There are many products currently on the market containing these active ingredients. Follow the manufacturer’s recommendation for the proper rate for bark beetle treatment. Bark beetle applications at the labeled rate should provide at least three months control of ips beetles.

When a preventively-sprayed tree later dies of beetle attack, it is usually for one of the following reasons: 1) the tree was sprayed after it was attacked; 2) the spray was applied at too dilute a rate; 3) the entire bark surface of the susceptible part of the tree was not sprayed; or 4) the material wore off and was no longer effective.

This is a case in Colorado US but in Europe tehe measures are and must be the same. Maybe this will help you. 

http://www.ext.colostate.edu/pubs/insect/05558.html

I think that the best results in your case scenario is a chemical treatment. Traps are slow and necesit aloat of time to be effective. In the case of a "wild rage" of IPS and when you have only a few trees to protect the best will be a chemical intervention folowed by 1-2 traps for the remaining insects.

Best to you.

Dear Golo and Negrea,

Thanks for your comments. I think in case of 100 years old spruces preventive spraying cannot be an option. Now, I have used three times acetamiprid (a systemic insecticide which was available) for the trunk till about 5-6 m height. Unfortunately, I have no helicopter. I will try OPI (organophosphate insecticides) and the Bauveria bassiana preparation which worked well in Slovakia. Certainly, the moribundus trees should be removed as quickly as possible by alpinist woodmen.

Hi András,

Below you will see the references to some other alternatives tested on Ips typographus that might be more easy to apply, and certainly cleaner than pesticides.

Repellents/response inhibitors such as non-host volatiles (NHV) or verbenone have shown to reduce the density of attacking beetles. Verbenone has been succesfully used to protect single trees like the ones you are mentioning, and is available from previously mentioned Contech. NHVs are not that easy to find, but the same company might help. We have purchased trans-conophthorin (a well known NHV) from them in the past.

Good luck!

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Zhang QH 2003. Interruption of aggregation pheromone in ips typographus (l.) (col. Scolytidae) by non-host bark volatiles. Agr. Forest. Entomol. 5, 145-153.

Zhang QH, Schlyter F, Anderson P 1999. Green leaf volatiles interrupt pheromone response of spruce bark beetle, ips typographus. J. Chem. Ecol. 25, 2847-2861.

Schlyter F, Löfquist J, Jakus R, 1995. Green leaf volatiles and verbenone modify attraction of european, tomicus, hylurgops, and ips bark beetles. In: Behavior, population dynamics, and control of forest insects. Proceedings IUFRO Working Party Conference. Ed. by F P Hain, S M Salom, F W Ravlin, T L Payne, K F Raffa, Ohio State University, 29-44.

Jakus R, Schlyter F, Zhang QH, Blazenec M, Vavercak R, Grodzki W, Brutovsky D, Lajzova E, Turcani M, Bengtsson M, Blum Z, Gregoire JC 2003. Overview of development of an anti-attractant based technology for spruce protection against ips typographus: From past failures to future success. Anz. Schadl.-J. Pest. Sc. 76, 89-99.