Bollettino dell Istituto di Entomologia (Guido Grandi) (2000) 54, 35-54

Massimo Faccoli (2000)
Bioecologia di Coleotteri Scolitidi - Ips typographus (Linnaeus) e specie di recente interesse per la selvicoltura italiana - II Contributo - Fattori naturali di contenimento di Ips typographus con particolare riferimento ai parassitoidi
[Bio-ecology of bark beetles - Ips typographus (L.) and species recently affecting the Italian forests - Part II Natural factors limiting the spruce bark beetle Ips typographus with special attention to its parasitoids]
Bollettino dell Istituto di Entomologia (Guido Grandi) 54, 35-54
Abstract: Notes about three parasitoids of Ips typographus (L.) new to Italy.
Tomicobia seitneri (Ruschka) (Hymenoptera Pteromalidae), Ropalophorus clavicornis (Wesmael) and Coeloides bostrychorum Giraud (Hymenoptera Braconidae), three parasitoids of Ips typographus, are recorded for the first time in Italy. Several specimens were trapped in Spring and Summer of 1998 in North-Eastern Italy (Friuli-Venezia Giulia) using spruce trap-trees baited for Ips typographus. Tomicobia seitneri (Ruschka) and Ropalophorus clavicornis are endo-parasites of Ips typographus adults. Eggs are laid in the pronotum of the host. At conclusion of the larval development, wasps emerge from the empty body of the host through a circular hole excavated in the middle of the host elytral declivity. Timing of generations as well as developmental time coincide with those of Ips typographus. The beetles are not paralysed by the attack but the female fecundity decreases. Conversely, Coeloides bostrychorum is an ecto-parasitoid laying eggs on Ips typographus larvae living under spruce barks. After five larval instar, larvae spin white cocoons in the host pupal chambers. Then, newly formed adults emergence chewing through the cocoons and bark. Coeloides bostrychorum, as well as T. seitneri and R. clavicornis, does not assure the natural control of the I. typographus outbreaks below economically acceptable threshold.
Breeding tests of Coeloides bostrychorum Giraud (Hym., Braconidae) spruce logs infested by Ips typographus (L.).
The possibility for a C. bostrychorum breeding was tested in laboratory using spruce logs artificially infested by Ips typographus. Two rearing experiments were performed at two different temperatures, 20°C and 25°C, and at two host densities (low and high). The rate of parasitism obtained in the first test at 25°C (11.4%) is lower than that observed in the field, and not adequate for supporting a mass-rearing of C. bostrychorum, while the average parasitism rate reached in the second test at 20°C (67.3%) encourage other experiments in this direction. The efficacy of C. bostrychorum does not appear affected by the density of host's breeding systems.
Winter mortality in Ips typographus (L.) and its natural enemies.
A study concerning on the winter mortality of Ips typographus and its natural enemies has been carried out on south-eastern Alps (Italy). Three attacked spruce trees were sampled three times (November, February and April) during the winter 1997/98 collecting infested bark disks (1 dm² each). All insects emerged from the samples were counted. Fungus species occurring under the bark were also checked. The mean number of Ips typographus occurring under the bark decreases of 49% passing from November to April. Winter mortality mainly affects larval stages and young adults. The same tendency was observed for the parasitoids Coeloides bostrychorum (48.5%) and Roptrocerus xilophagorum (47.5%). Contrary, Diptera Sciaridae populations decreased of about 65.5%. The low occurrence of entomophagous fungi (Bauveria bassiana 10.5% and Verticillium lecanii 4.7 % of the samples) do not explain the high mortality of the insects.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: Italian)
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Database assignments for author(s): Massimo Faccoli

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
population dynamics/ epidemiology
Research topic(s) for beneficials or antagonists:
surveys/distribution/isolation
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ips typographus	Spruce (Picea)	Italy
Tomicobia seitneri (parasitoid)	Ips typographus		Italy
Coeloides bostrychorum (parasitoid)	Ips typographus	Spruce (Picea)	Italy
Ropalophorus clavicornis (parasitoid)	Ips typographus		Italy