Monochamus galloprovincialis (pine sawyer)

Infested timber will have ovipositional scars on the bark. Bark removal around such scars will show the feeding galleries and tunnels made by the larvae. Larger round exit holes may be seen where adults have emerged. Needles and shoots, up to 3 years old, will show marks from adult grazing and may appear dry. Needles may also fall early as a result of such feeding activity (Prozorov, 1929). Branches may be ring-barked. If inspected carefully, one may notice grazing marks visible on the surface of green pine cones where the thin epidermis has been removed during adult feeding.

Recommended control measures against bark beetles in general are the debarking of all felled wood exceeding 30 cm in girth immediately after felling, and the debarking of all stumps, together with a prohibition of thinning young, unbarked pine during the growing season. All weakened and dying trees should be removed. If it is not practical to remove infested trees, it is better to fell them and remove bark without delay, so as to prevent oviposition and to destroy the eggs already laid underneath the bark and any of the emerged larvae (Rodd, 1914).

The use of trap logs was advocated by Schnaider (1954). The logs should be raised from the ground so as to expose the entire surface to attack and to prevent rotting. The logs should be debarked when the larvae in them are near pupation, and the removed bark can be left lying about, as the larvae soon die owing to exposure or attack by ants or other predators. Trap logs should subsequently be burned. Trap logs can be a key method of control and should be set in three phases, the first in early May, which are then debarked in late June, the second in mid-June (debarked in late July) and the third in mid-July (debarked in late August or early September). Trap logs should be set in clearings or under canopies with no understorey. When debarking is too late and damage has started, chemical control is recommended (Dominik, 1981).

Any standing trees that are attacked can be promptly felled in the spring or summer and debarked. As a result of these measures, infestation levels can be considerably reduced (Megalov and Bazhenov, 1927). Debarked logs can be protected with an aqueous emulsion of permethrin or fenitrothion (Dominik, 1981). As a substitute for debarking, trials in Poland used chemical spraying of the bark of Pinus sylvestris trap trees. Dimethoate was also effective (Szmidt and Wachowiak, 1973).

Laboratory trials showed that all isolates of a conidial suspension of Beauveria bassiana tested by spraying onto apical shoots of Pinus nigra and kept at 23-27°C and 90-100% RH in plastic boxes with adult M. galloprovincialis were pathogenic, with mortality levels near 100% (Francardi et al., 2003). Further development work would be required to develop a field control programme.

All the European Monochamus species live in association with dead and declining conifers and are usually considered secondary forest pests. The direct economic importance of M. galloprovincialis larvae results from the economic losses they can cause to felled trees by forming boreholes and pupal chambers in the wood (Tragardh, 1929), causing timber to be downgraded in quality and hence value. For example, badly-infested felled trees can be sold as firewood and not as timber, which greatly decreases their value. However, larval tunneling damage is normally only significant if logs are left in forests for a long time after they have been felled (Smith et al., 1997). In badly infested areas, 73.5% of dead trees can be infested with M. galloprovincialis (Rodd, 1914).

In well-managed forest conditions, where felled logs are not left for long periods, Monochamus spp. are not generally considered to be a serious pest in their own right. In Europe they are considered a secondary pest (Richter, 1962; Sierpinski, 1971), for example following outbreaks of Lymantria monacha (Richter, 1962). Nevertheless, in the past M. galloprovincialis larvae have caused considerable injury to felled pine timber with or without bark (Dominik, 1960), and have attacked healthy standing trees and standing trees weakened by fires or storms (Sokanovskii, 1929; Hellrigl, 1971a).

Economic damage is not restricted to that caused by larvae, since adults feed on live host trees. Newly-emerged adults feed on the needles and on the tender epidermis of shoots up to 3 years old. More mature older adults feed on the bark of the trunk and larger branches, but still consume needles. Adults can cause indirect damage to pine cones by maturation feeding on the shoot-bearing cones. Adult M. galloprovincialis occasionally cause direct damage to cones by feeding on the epidermis of green cones (Berezina and Kurentzov, 1935). Adults can also ring bark branches in the crown of trees that are then damaged or blown down by wind (Polozhentzev, 1926). Adults that attack the upper parts of trees will render them susceptible to attack by secondary pests, but the greatest damage to live hosts results from the adults stripping off the epidermis from the growing shoots and from needles (Polozhentzev, 1926). The oviposition holes created by females also damage hosts by allowing secondary pests and pathogens access into the bark.

The economic importance of Monochamus species increased dramatically when it was recognised that they were the primary vectors of the north American phytoparasitic nematode Bursaphelenchus xylophilus, a species of quarantine concern. Monochamus adults carry the nematode and transmit it through the feeding wounds they cause on healthy pines or through oviposition scars made by females (Evans et al., 1996) (see also Phytosanitary Risk).

As well as damaging felled timber left in forests, M. galloprovincialis can also attack timber in warehouses, where chemical control may be necessary to protect the timber (Tsankov, 1975).