Pissodes castaneus (small banded pine weevil)

Feeding damage to young Pinus by adult beetles is usually insignificant. They make small holes in the young bark of fine branches and stems and, by reaching the inner bark, cut the resiniferous canals. From these holes resin exudes, so that adult feeding is revealed by the presence on the bark of small droplets of resin. Upon evaporation these droplets solidify and become white. These symptoms are sometimes accompanied by yellowing and death of the shoot extremities. Perfectly circular exit holes made by emerging adults are also visible on the lower parts of the trunk.The larvae of P. castaneus tunnel between the bark and the wood of young Pinus producing slightly tortuous galleries which proceed downwards in the inner bark and terminate at the root collar. A radiating gallery system is produced in stems of sufficient diameter, from eggs deposited in a mass. In stems of small diameter, the galleries are entirely longitudinal and descend as far as the root collar, where the bark is thickest. They may reach the phloem region of the roots when egg laying has taken place at the base of the trunk, as usually occurs in young Pinus. The galleries become wider with the development of the larvae and are obstructed by compacted sawdust and excrement. Their large dimensions, irregularity and lack of maternal galleries readily distinguish them from those of scolytids.The larval galleries prevent the circulation of sap, causing a slow desiccation which is manifested by wilting and general yellowing and browning of the needles, and then by death of the tree. Partial browning of needles is also caused by gall midges (Cecidomyiidae), but their small reddish larvae are visible in the sheaths around the needles. If the larval galleries of the weevil do not encircle the stem, some green shoots remain on the otherwise wilting plant. At the base of the trunk, sawdust and a sap exudate are sometimes visible. The detachment of bark, although less frequent in young plants, is a serious symptom of Pissodes attack. This bark loss allows the easy detection of the larval galleries and cushion-like pupal chambers in the lower stem. In trees with larvae and pupae situated in the root neck, the stem is swollen at this point and the trees easily lose their hold in the soil. Figures showing characteristic damage are given by Zarco (1949) (colour plate), Anon. (1970) and Kudela (1974).

Preventive control can be achieved by ensuring vigorous growth of quality planting material on the best soil. Good husbandry involves removing dead wood, which could act as oviposition sites, or any infected trees or parts. Infected trees should be uprooted and burnt, rather than felled, since pupation occurs close to the ground on young stems. Artificially weakened 'trap' trees can be established in a stand to attract oviposition; these are subsequently carefully removed and burnt. Similarly, piles of bark fragments and twigs can act as hibernation traps.Chemical control is rarely necessary, and is difficult, as the adult flight period extends from May until September. Satisfactory, though incomplete, control was achieved in Yugoslavia by spraying the trees with an insecticide treatment including malathion (Grujic and Milanovic, 1963). Cobos and Robredo (1982) recommended the use of 5% fenitrothion dust, applied from aircraft, when the intensity of attack is high and the area requiring treatment is very large. The high rates of parasitism observed in P. castaneus suggest that parasitoids could be manipulated to improve natural control. No biological control project has been carried out against P. castaneus, but parasitoids of P. castaneus have been considered for introduction against the congeneric species Pissodes strobi in Canada (Kenis and Mills, 1994, 1998). Phytosanitary measures must be carried out to prevent the introduction and establishment of P. castaneus in uninfested regions. Plants for planting of Pinus spp. should be visually inspected for P. castaneus, paying particular attention to the possibility of the weevils boring into young shoots. Wood should be debarked before shipment.

P. castaneus is an important pest of Pinus spp. in France, UK, Russia, Finland and Spain where large numbers of young trees in new plantations may be killed. In addition, attacks by this weevil cause serious losses of young Pinus in both natural stands and plantations in southeastern Europe and the eastern Mediterranean (Kailidis, 1964). In Portugal, P. castaneus shows a preference for grafted P. pinaster, tunnelling in small branches and endangering the success of the graft. In plantations grown for seed, infestation resulted in severe reductions in yield (Silva and Nogueira, 1967). It almost exclusively attacks 2- to 15-year-old trees, but even 100- to 120-year-old trees are not immune. Development may also occur in felled pine logs and split firewood. The most serious damage is caused by the larvae, whereas the adults cause little damage.Usually this weevil is a secondary pest of conifers which have been weakened in some way. Often it may be associated with or succeed another pest, for example Pityogenes bidentatus. In the south of France, P. castaneus is a principal pest of Pinus attacked previously by the coccid Matsucoccus feytaudi (Carle, 1974; Arzone and Vidano, 1981); however, Alauzet (1969) showed that from 1962 to 1963, 58% of trees were destroyed by P. castaneus alone and it may, therefore, also be a primary pest of P. pinaster in France.