Insect communities in barked and unbarked Pine Stumps, with special reference to the large Pine Weevil (Hylobius Abietis L., Col., Curculionidae)

Abstract

Summary About half the number of stumps of recently felled Scots pine (Pinus sylvestris L.), selected so as to be evenly distributed over the plots concerned, were barked. Equal numbers of these and of the unbarked stumps were uprooted later, and the larvae, pupae and adults of Hylobius abietis L. and other insects in the stumps and roots were counted. Other readily obtainable data were also collected. In one experiment, cages were put over the stumps to trap the emerging H. abietis adults. On comparing the Hylobius populations in the two categories of stumps it was seen that barking at the beginning of the oviposition period or about 1, 2 and 6 months before it, did not result in a significant reduction of the numbers developing in and emerging from the stumps and roots. Even clearing the soil round the stumps and main roots, carefully barking the stumps to a greater depth than usual, replacing the soil and treading it down did not produce that effect. Nor was it obtained by barking at a time during the larval stage when the greatest possible number of larvae could be destroyed. The latter experiment was carried out in both thinned and cleared plots, the others in either of the two types of plots. It is concluded from a study of the literature on the subject and from these results that the efficacy of barking as a control measure against H. abietis is unproven and that some of the obvious modifications of the method are definitely ineffective. There was no consistent difference between the numbers of Hylobius developing in stumps in cleared or in thinned plots. The time required for development and emergence from the stumps and roots was 14–18 months, presumably corresponding to a two‐year cycle from one egg stage to another. In some individuals the underground period was either 3–6 or 12 months. Most adults appear above ground in August. Less than 10 % of the eggs reached the adult stage on one cleared plot, the greatest mortality occurring in the early larval stages. Normally no H. abietis will be present in the stumps after the second summer after felling. The latter statement also applies to all Scolytids in clear‐felled plots; in thinned plots small numbers may persist after that. Hylastes ater Payk. was the most numerous of these Scolytids. Where the adults of that species could choose between freshly barked and unbarked stumps greater numbers of them invaded the former, but the difference in numbers was offset later by the greater mortality in the brood in the barked stumps. It is believed, however, that the total mortality in the barked and unbarked stumps together remained the same, and that even the barking of all the stumps in a given area would not have affected the total mortality. Barking prevents pine‐shoot beetles (Myelophilus piniperda L., Scolytidae) from breeding in the stumps, but not many are likely to do so under the conditions prevailing in the Netherlands; so the operation is not considered worth the expense. Other Scolytids regularly found in the stumps were Hylastes opacus Er., H. atten...

Evict or infect? Managing populations of the large pine weevil, Hylobius abietis, using a bottom–up and top–down approach

“…Destruction of breeding sites was practised historically in many countries as the principal method of reducing the number of adult H. abietis emerging onto a site (Elton et al, 1964). Eidmann (1979) reported that where stumps were removed, confining weevil development to torn roots and stumps felled during forest thinning, H. abietis populations could be reduced by up to 50%.…”

Effects of Norway Spruce (Picea abies) Stump Debarking on Insect Colonization in the Polish Sudety Mountains

“…Higher colonization intensity was observed in the bark samples collected from debarked stumps as compared to samples from untreated ones. This was most likely the result of enhanced resin secretion by debarked stumps (Elton et al 1964). To date, information regarding the effects of debarking on the colonization of spruce stumps by insects has not been available, yet those on pine stumps have been investigated and reported in the literature.…”

“…The insects are attracted by volatile emanations from the fresh resin (Nordlander et al 1997;Byers 2004;Schlyter 2004). Debarking of the aboveground basal part of stumps (hereafter referred to as stump debarking) immediately after tree felling was first recommended in Germany at the end of the 19th century (Elton et al 1964) as a method for reducing insect pest populations in Scots pine Pinus silvestris (L.) stumps. It was believed that such a treatment would prevent stump colonization by cambiophage beetles and promote wood drying, making stumps unattractive for insects.…”

“…In the first half of the 20th century, Scots pine stump debarking to reduce large pine weevil colonization was commonly applied in a number of European countries, including the Netherlands, France, Estonia, Russia, and Poland (Brammanis 1930;Butovitsch 1931;Ossowski 1941;Hubault 1945). A milestone in the debate on the appropriateness of debarking treatments was the publication of results obtained by Elton et al in 1964. With regard to the large pine weevil, the authors compared insect assemblages on debarked and untreated Scots pine stumps and found no difference in insect colonization (population numbers and species…”

Effects of location of Norway spruce (Picea abies) stumps on their colonisation by insects in the mountains

“…Scolytinae) in conifer stumps were mainly of the genus Hylobius that is represented by weevils H. abietis and Hylobius pinastri. These species are known to be extremely pervasive pests of reforested areas (Wallace 1953;Więckowski 1957;Elton 1964;Day et al 2004). The results of studies conducted in the Polish mountains confirm that H. abietis belongs to the most abundant cambio-xylophagous species colonising P. abies stumps (Starzyk and Sek 1983).…”