The Wood-Borer Pest

Sun (Auckland), Volume II, Issue 517, 21 November 1928, Page 7

The Wood-Borer Pest

AFFECTED BY KILN DRYING Opinions of Scientists DAMAGE to the extent of thousands of pounds annually is done by the wood borer in New Zealand, and much thought has been given by builders and others to methods of treating timber in order to keep it free from the ravages of this pest. The following data on the subject will therefore be of interest to those who wish to deal effectively with the pest. *

There Is no method known for keep-, ing these insects under observation in the larval (grub) stages, as during this time they are inside the wood making the well-known “galleries.” Even cutting open a section of timber and placing a transparent medium over a larva in a gallery is ineffective, as the insect either perishes or immediately tunnels out of sight. The food is the particles of wood which are rasped off, in forming galleries, which are swallowed. Nutriment is extracted and the great bulk which is useless to the larva is passed thi-ough the body. This does not mean that all the wood rasped away is eaten, as it is really only a percentage which is consumed. Adults (beetles) appear in Novem-ber-January. They may be collected and confined with wood, when egg-lay-ing will follow. The wood must be examined at least once a week for eggs, and to induce egg-laying only undressed timber must be used. Pieces 6ft x lin x Sin are about the best size, and these may be placed side by side in any suitable container with a detachable lid. The adult beetles, I believe, do not require food. The eggs are laid in the cracks and under uneven parts of the timber and may readily be seen with the assistance of a strong hand lens or a microscope. The young larvae hatch from the eggs and bore straight into the timber, so if one wishes to get successive stages in the life history it will be necessary to have a large number of pieefes of wood, all infested with eggs at the same time. By splitting open thoroughly one piece a fortnight it is possible to obtain a complete life history. The various stages may be preserved in alcohol or methylated alcohol. T. E. Snyder, entomologist, Bureau of Entomology, United States Department of Agriculture, writes as follows: The heartwood is immune to attack by Lyctus powder-post beetles and should be used wherever possible. SIMPLE REMEDIES Simple remedies to use in case of small quantities of stock are trimming off and burning infested sapwood edges. Dipping in or spraying infested stock •with orthodichlorobenzene will kill the larvae in the wood. The heat generated during the ordinary dry kiln operation is sufficient to kill certain borers infesting wood. Experiments by Dr. F. C. Craighead have shown that the larvae of the redheaded ash borer (Neoclytus erythrocephalus Fab.) can be killed in any kiln process which can be considered practical for the seasoning of ash, regardless of the thickness. Such treatment will also prevent further attack by the red-headed ash borer. In the case of Lyctus powder-post beetles, however, the temperatures of the ordinary kiln process are not fatal to the larvae. Recent preliminary experiments conducted with the U.S. Navy Department have shown that higher temperatures are necessary I and that subjecting seasoned wood to

i temperatures of ISO degrees F. in dry kilns is an effective remedy. In order to kill the larvae in infested wood, it is necessary to run the infested material through the ordinary process and at the end of this operation have the temperature raised to 180 degrees F. or over for a short period—one halfhour or longer, depending on the dimensions of the material, or rather of the sapwood. In the “Journal of Forestry,” F. C. Craighead, of the Bureau of Entomology, and W. K. Loughborough, Forests Products Laboratory, deal with the temperatures fatal to larvae of the red-headed ash borer, as applicable to commercial kiln drying. The outstanding deductions from this study were that the larvae of the red-headed ash borer are killed in any kiln process which can be considered practical for the seasoning of ash, regardless of the thickness. Even temperatures as mild as those used in Schedule 2, Specification 20,500 A, Bureau of Aircraft Production, which range from 105 deg. to 135 deg. F., are fatal to them. Subjecting infested material to a temperature of 116 deg. F. for 45 hours resulted in 100 per cent, death of the larvae. Temperatures of about 125 deg. to 130 deg. F. will kill the larvae within an hour after the wood becomes heated through. Dry heat is fatal to the larvae at a lower temperature than hot water for the same period. Water at 125 deg. F. for an hour was fatal to only 75 per cent, of the larvae treated, while dry air at 125 deg. F. resulted in 100 per cent, death in two minutes. The time required to produce 100 per cent, death in dry air at 120 deg. F. was 10J minutes, while the same effect was produced in water only after 2J, hours.