UNIVERSITY OF CALIFORNIA. AORICULTURAL EXPERIMENT STATIOK. BUIiliETIN No. 73. The Use of Hydrocyanic Acid Against Scale Insects. The generator, in general terms, contiata of a «heet-iroQ cylinder, or tank, held between two pieces of plank, one of which forms the cover, and the other a movable base which is carried up and down by an eccentric placed be neath. The cover holds two receivers (one for the acid and one for the cyanide and soda) and two tubes opening into the exit pipe which passes over the generator from the blower. A Note.— As staled in a previous University Bulle- tin (No, 71, June 12, 1887), a special investigation was undertaken by this station at the request of or- anf^e-growers of San Gabriel, Los Angeles county, ^ to determine the practicability and efficiency of ' gaseous insecticides. The results obtained were so j- . __ satisfactory that' the orange-growers who bore the n^avy volume of air, carrying with it the gas, is extra expenses of the first experiments urged the forced by the blower into the tent through a advantages of continuing the work, and the Board Si-inch pipe, and after diffusing is again carried of Supervisors made an appropriation to cover ex- back by a similar pipe to the blower, thus es penses. the work to be done under the auspices of tablishing a continuous circulation and stirring the County Horticultural Commissioners. For this ap of the gas during the treatment, reason I he following description of later experiments - ... ;ind their results takes the form of a report to the local authorities of Los Angcl-is county. To the Board of IJorilcultnral Commission ers of Los Angeles County — Gentlemen; I herewith transmit a preliminary report of in vestigations, carried on at your request, relat In the pipes leading to and from the tent are two joints — one at the elbow close to the gen- erator, used as a disconuecbing joint when the apparatus is movei; the other, about three feet from this point, is used as the disconnecting joint when two tents are worked with the same generator, and becomes only a flexible^ the tree is made of heavy bed-ticking, thoroughly oiled with lin- seed oil. This cloth serves the purpose best, as it is very closely woven, is pliable and easily folded. Practice has shown that much labor ing to the uae of gas as an insecticide against | joint when one tent is used; the former in this' the cottony cushion scale insect ( /ceryct />Mr Ljase becomes the disconnecting j^int. The iihasi). Tne work was a continuation of that I opening of the injecting pipe is covered with a carried on some time ago, and consists mainly | perforated cap which distributes the gas when in devising means for the easier application of , pumped into the tent, the Ra-j which was found by the earlier experi- ! fhe lent for covering ments to be the most efficient. Iq resuming the work, to carry out the gen- eral principles of application as set forth in the last report, it was found necessary to vary con- sideriiVily the form of apparatus and prelim- time can be saved, and less injury done to inary preparation of materials, for the purpose the tree, by having a tent which passes easily of increasing the rapidity and certainty of over the tree, with cloth enough to make a application. A fan-blower capable of carrying olose connection at the bottom with the earth, a heavy volume of wind replaced the pump pre- The cloth is folded out at the bottom rather viou=»ly used, and this ntceesitated a change in than folded in, as in the older treatments, and the foim of the generator. ^ its margin covered with d rt, thus increasing M iny experiments were made to determine the area of soil treated without materially in- the most convenient methods for using the creasing the volume within which is to be filled chemicals. The old way of mixing the soda ^ith gas. and Cj anide in the generator was found to The tent should be made somewhat bell- be too slow and uncertain to be practicable, shaped, having a "flange" at the bottom of Often a heavy crystalline coating formed around sufficient size to move outside of the main tent the mixture and prevented complete action at all times, and should fold over like a glove when the acid was added; again, when the two when the tent is remoyed. It should also be salts were not m'xed, tne usefulness of the car- large, so that the points of attachment of the bonate as a protection to tho foliage was often guy ropes may be drawn close to the pul- les^ened. In order to avoid this difficulty, it leys in the corners of the framt ; thus, when j became necessary to reverse the order of appli- wide spreading trees are to be treated, the tent cation and inject slowly the salt mixture upon ^an easily be drawn over any branches included the acid as given in the directions below. ^ within the frame. \ri attempt was made to use each ingredient The support of the tent, devised by Mr. separately the soda being in a solid form, but Titus, i^ a very ingeniously contrived fcaffold- the same difficulties of uncertainty and slow- jng mounted on wheelf, which terve to move it ne88 Mere experienced. Ifrom one tree to another. Its dimensions are 26 feet lugh, with a base 2Gx20 feet. Its upper part is 20x12, and carries upoa the top a roller made of galvan'zsd iron (6 inches in diameter and 12 fc^et long), upon which the tent is rolled when taken from the tr