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Monitoring of bark beetle population

According to the State forest pathology monitoring bark beetle mass outbreak in the Moscow region is over. However bark beetle record in pheromone traps and infested trees in 2016 showed available micro outbreaks of this pest.

Pheromone traps enabled identification this pest evolution phonological stages in 2016 it had a double generation with one sister breed. Bark beetle swarming continued practically constantly. Due to warm weather in August and early September in 2016 2nd generation evolution completed successfully. Wintering started in mid September. Most share of species wintered in under bark galleries in trees in decline edges. Beetles of 1st (main) and sister generations played a key role in spruce infestations.    

Over summer period (from May 3 to September 9) average catch per a trap was 1710 beetles and in May-June around 1160 beetles. Such bark beetle population is close to a threshold and shows available risk of the pest outbreak development. In fact single freshly infested trees and windfall were found in June, 2016 and a micro bark beetle outbreak a cluster of bark beetle attacked trees (12 pcs.). Bark beetle 2nd generation infested more 21 trees and the outbreak doubled. Diagnostics of these trees by external features was extremely difficult since in autumn and early winter they had green needles. Bark beetle attacked trees become evident due to fall of bark and needles only in February this year.   

In 2017 bark beetle population monitoring went on in declining outbreaks in 2 stationary plots in Moscow region spruce woods. In 1st plot in 80-100 year old spruce forest barrier traps were set in late April. In 2nd plot located in territory of “Mosoblles” training experiment forest district 3 traps were set in early May not far from spruce decline outbreak (50-70 м), that died mostly in 2013 and singularly in 2014. .

Beetle swarming started on April 30 and due to warm and dry weather was intensive. Then in contrast to 2016 swarming stopped and during a week May 7-14 there were no beetles in traps. It was due to extreme cold. On May 7 was a soil frost. It snowed on May 9. May 10-11 until May 12 morning it snowed and rained, May 13 a small rise of air temperature to 5-10 degrees.

Unfavourable for insects and optimal for spruce growth weather resulted in bark beetle population reduction. Total catch of beetles over May-June, 2017 was 465-891 species (on average 800 pcs.). In comparison with the previous year a trap catch was 360 beetles less and approximate bark beetle reproduction coefficient assessment  – 0,69.

In 2nd plot over survey period an average trap catch was less than 1500 bark beetles and total catch was 4350 species that proves its low density in this forest.

A detailed visual record of bark beetle infestation of spruce forest was conducted in forest pathology monitoring. Bark beetle evolution record was conducted in control trap trees as well as in bark beetle infested trees. 

In 2017 sister generation beetle emergence started in June. Already emerged young beetles started to join them. Its most massive joint swarming was on July 2 when an average trap catch was 341 pcs.

 

Picture outline. Fresh spruce dry wood attacked by bark beetle 2nd generation partially with green needles and fallen bark (right) in a local outbreak March 18, 2017.