179670a0Nature1794561195703306706700028-0836195710.1038/179670a0ukNatureNatureNATUREnatureNature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public./nature/journal/v179/n4561issueJournal homeArchiveCurrent issueAdvance online publicationPrivacy policySubscribeNature Publishing GroupCurrent issue179670a0Use of Gamma Radiation for the Destruction of Wood-boring Insects
AU  - BLETCHLY, J. D.
AU  - FISHER, RONALD C.Entomology Section, Forest Products Research Laboratory, Princes Risborough, Aylesbury, Bucks. Jan. 18.COMPLETE eradication of wood-boring insects in timber in buildings is difficult to achieve, particularly in structural members of large dimensions, often inaccessible for thorough surface treatment. Moreover, the value of insecticidal fluids and of fumigants is restricted by the impenetrability of many timbers and varies according to the species of insect and extent of attack. Radiation treatments may offer a means of reducing this problem of penetration, especially in large built-in timbers, such as oak infested by the death-watch beetle, but before their possible application in practice can usefully be considered, accurate data are required upon the effect of different dosages on the various stages of development of the insects.With the object of obtaining this information, a series of experiments on a laboratory scale has been undertaken, and is still in progress, at the Forest Products Research Laboratory in co-operation with the Atomic Energy Research Establishment, Harwell, where the radiation treatments of experimental material are carried out. The investigations have so far been confined to insects free from wood or within samples approximately half an inch in thickness. The powder-post beetle, Lyctus brunneus Steph., which will complete its life-cycle in three to four months in oak sapwood at 25 C. and 75 per cent relative humidity, was used in the initial work ; but this has now been extended to include the common furniture beetle, Anobium punctatum Deg., and the death-watch beetle, Xestobium rufovillosum Deg., both of which are more difficult to handle in the laboratory.
The following brief summary of the results to date indicates the possibilities and limitations of this type of treatment for the destruction of wood-boring insects : a progress report giving fuller details is being published elsewhere1.
Using cobalt-60 as a source of gamma rays and measuring dosages in rontgens, it has been found that the eggs of Anobium and Xestobium can be killed by exposure to 4,000 r., if irradiated within one to four days of laying, but that their resistance increases rapidly as they develop. For example, dosages between 48,000 and 68,000 r. are necessary to kill mature eggs of Anobium, and in excess of 32,000 r. for Xestobium ; but there are indications that eggs irradiated at much lower dosages give rise to larvae which do not survive. High dosages are needed to kill larvae of Lyctus quickly, but their development is arrested by treatment at 8,000 r. Incomplete results are available for Anobium larvae, but it appears likely that their reaction is similar : the larvae of Xestobium have not yet been studied.
Irradiation of Lyctus adults at dosages up to 48,000 r. did not inhibit egg-laying ; but after treatment of both sexes of Anobium, Lyctus and Xestobium at 8,000 r. no fertile eggs were laid. Of the insects studied, only in Xestobium do the adults remain for several months within the timber before emerging, and this may be an important practical consideration in relation to the period during which infested timber containing adults as well as larvae could most effectively be irradiated. Further work, with particular reference to this insect, is justified by the results so far obtained and is now in progress.
The investigation forms part of the programme of the Forest Products Research Board and is published by permission of the Department of Scientific and Industrial Research. We thank Dr. W. Wild, officer -in-charge of the Radiation Chemistry Group, Atomic Energy Research Establishment, Harwell, for the facilities provided by his Department and for his co-operation.Bletchly, , J. D., Xth Int. Congr. Ent., Canada, 1956 (in the press).