Transactions of RHASS Volume 1940 - Page 055
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| Year | 1940 |
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98 INSECT AND OTHER PESTS OF 1939. Despite the fact that potatoes are susceptible to wireworm attack the seed is rarely so damaged as to affect the luxuriant growth of the tops. Damage occurs when the \Vireworms migrate to the tubers in late summer and autumn and riddle them with holes. Although potatoes do well as a second crop on old ploughed grass land, where they are favoured by the decaying mat of old turf, they are thereby liable to heavy attack by Wireworms to which the turf is no longer so attractive as it was the ,first year. Thus in order to reduce the risk of heavy damage to the crop in infested land it might be well to take potatoes as a first crop. This procedure is particularly advisable when the land is broken too late in the year for sowing to winter wheat or other winter crops. Potatoes, again, are also a suitable crop on land ploughed in late winter or early spring and may be considered as an alternative to oats, barley, or sugar-beet. Remedial M comma—At the present time there is a pressing need for a quick-acting and cheap soil insecticide'for use against Wireworms and other destructive soil-inhabiting insect and allied pests. Dressings of crude naphthalene at the rate of 3 to 5 cwts. per acre are frequently recommended, but the results attending its application are very variable, depend- ing on the texture of the soil and weather conditions. The vapour of naphthalene, too, has primarily a repellent effect on insects, which causes them to withdraw out of range before it has reached a toxic concentration. From recent experi- ments Miles and Cohen 1 have concluded that dressings of 3 cwt. per acre do not destroy Wireworms, but merely afford some relief by repelling the insects from the crop for a short period. Better results have attended the use of calcium cyanide as a soil fumigant. Horsfall2 in America was the first to test its lethal effects upon Wireworms, and he claimed that it destroyed 81 per cent of the wireworm population of an infested field in five days. By combining baits to. induce localisation of \Vireworms, along with later dressings of calcium cyanide applied to the areas where the insects had gathered, Campbell 3 introduced a method whereby the cost of treatment could be materially reduced. A further important contribution to the subject of wire- worm control was that of Spuler,4 another American worker, who showed that germinating seeds of peas, beans, and corn 1 Miles, H. V“, and Cohen, M., 1939. “ Investigations on \Vireworms and their Control.” Jour. Roy. Lanes. Agrie. $00., repr., p. 13. 2 Horsfall, J. L., 1924. “ Possibilities of Granular Calcium Cyanide as a Control Measure for W'irewornis.” Jour. Econ. Exit, Vol. XVII., p. 160. 3 Campbell, R. E., 1924. “ Preliminary Report on the Use of Calcium Cyanide as u, Soil Fuinigant for \Vii'eworms.” Jour. Econ. Exit, Vol. XV11., p. 562. “ Spuler, A., 1925. “Baiting \Virewornis.” Jour. Econ. Enh, Vol. X\'III., pp. 703-707. INSECT AND OTHER PESTS OF 1939. 99 are more. attractive than other baits such as bran, .flour, sliced tubers. Seed is easily sown in rows, and when it has sprouted the seedlings serve to denote the places of assembly of the Wireworms. Two weeks after the seed has been sown the rows are fumigated with calcium cyanide. VVh11st the measure of control achieved by fumigation was as high as _75 to 80 per cent, the cost of £6 to £9 per acre was likew1se high where the cyanide was applied at the rate of 200 to 400 lb. per acre. In Britain Miles and Pctherbridge,1 following the lead of previous American investigators, were able to confirm the fact that germinating seeds were more attractive to Wireworms than dead baits. Both wheat and oats proved suitable. Wheat was drilled in rows three feet apart. Calcium cyanide was applied to the bait-rows after two weeks at the rate of 90 lb. per acre, and the cost, with cyanide at 1s. 2d..per 1b., was £4, 10s. per acre. In 1938 Petherbridge2 eprOIted the differential attraction of wheat and sugar-beet for the protec- tion of the latter against wireworm attack. The sugar-beet was inter-sown with wheat to which the VVireworms gathered in preference to the beet seedlings. The whole question of soil fumigants and wireworm control has been recently studied by Miles and Cohen.3 Various fumigants have been tested both in laboratory and field experiments. Applications of mixtures of (I) mustard dress and naphthalene, (2) fuller’s earth, naphthalene, and carbon bisulphide, and (3) fuller’s earth, naphthalene, and cyanide were said to reduce the amount of serious wireworm damage to tubers. The results obtained by the authors are suggestive, but further experimentation will be required before these mixtures could be recommended for adoption in wireworm control. The question of cost, too, would require to be closely considered. Experiments With a variety of fumigants have also been carried out by Ladell 4 at Rothamsted, who found that mixtures of orthodichloro- benzene and paradichlorobenzene reduced the Wireworm population of selected plots by 69 and 62 per cent, and crude naphthalene by 60 per cent. There was no means of deter- mining how much the reduction of the WH'CWOI'ln- population by any particular treatment was due to repellent action and how much to lethal effects. It was, however, realised by Ladell that the reductions of the wireworm population which he obtained were too low to be of significant economic value. 1 Miles, H. \V., and Potlierbridge, F. It, 1927. “ Investigations on the Control of \Vireworms.” Ami. App. Biol., Vol. XIV, pp. 359-386. ” . 2 l’etherbridge, l". R., 1938. “ VVireworrns and Sugar-Beet. Jour. Min. Agric., Vol. XLV., No. 1, pp. 23-27. _ _ H 3 Miles, H. \V., and Cohen, M., 1939. “Investigations on \Vireworins and their Control.” Jour. Roy. Lanes. Agric. Soc., repr., pp. 1-35. I n ‘ Ladcll, \V. K. 8., 1938. “ Field Experiments on the Control of VVireworms. Ann. App. Biol., Vol. XXV., No. 2, pp. 341-389. |
| Title | Transactions of RHASS Volume 1940 - Page 055 |
