Transactions of RHASS Volume 1940 - Page 059
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| Year | 1940 |
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106 INSECT AND OTHER PESTS OF 1939. (3) M crcuric Chloride—Johnson 1 is our authority for the introduction of mercuric chloride as a control agent for eel- worm. In 1932 he carried out a series of experiments to test the efficacy of weak solutions of mercuric chloride in reducing Tomato Sickness in soils heavily infested with eelworm cysts. The chloride was applied at the rate of 1 gallon per square yard in strengths varying from 1 in 500 to 1 in 150. The treated plots produced plants which were markedly more vigorous than those on untreated plots and yielded a larger crop of fruit. The roots of treated plants remained healthy and showed only a few cysts, whereas the roots of untreated plants were rotten, and cysts were readily detected on them. CHRYSANTHEMUM MIDGE (Diarthronomyia chrysanthemi)? The Chrysanthemum Midge was first recorded as a destruc- tive pest of Chrysanthemums in North America in 1915, in which year, too, it was first found in Canada at Victoria in Vancouver Island. It was at Victoria some years later that I was able to see for myself the damage of which it was capable on glass-house Chrysanthemums as well as in those grown out-of-doors. To-day it is fairly well distributed throughout the United States from coast to coast, and it has now established itself in Eastern as well as in Western Canada. In America the Chrysanthemum Midge is considered to be of European origin, but so far as Britain is concerned it was not until 1927 that its presence on Chrysanthemums was discovered in England in Hertfordshire and Essex. A year later it appeared in a single district of Lancashire, and it was not again until 1936 that a further outbreak of the pest occurred in England. This and the infestation of 1927 were both traced to varieties imported from the United States. In 1937 the midge was discovered in a nursery in Northern Ireland, near Belfast, and here it was found to have been introduced in cuttings which came from an infested nursery in Sussex. The latest addition to the British record comes from Scotland, where the midge was identified in a Lanark- shire nursery in December 1939 and also in adjoining green- houses and gardens. Damage—The cone-shaped galls (Fig. 7) which are dis- tributed over the leaves, stems, and buds of affected plants are diagnostic of an infestation. In severe attacks the plants be- come distorted, growth is retarded, and flowering is inhibited. 1 Johnson, L. R., 1936. “ Trials of Mercuric Chloride for the Prevention of Potato Sickness.” Ann. App. Biol., Vol. XXIII., No. 1, pp. 153-164. 2 Barnes, H. F., 1940. “ The Biology of the Chrysanthemum Midge in England." Ann. App. Biol., Vol. XXVII., No. l, p. 91. INSECT AND OTHER PEsrs OF 1939. 107 Young leaves, instead of expanding with growth, often remain folded and assume a rosette-like appearance. Fig. 7.——-Chrysanthemum shoot showing galls of the Chrysanthemum Midge on the leaves and stem. From nature. About natural size. Life-history.—The adult midge is a minute orange-coloured fly about 7'3 inch long and with long yellowish legs. The files |
| Title | Transactions of RHASS Volume 1940 - Page 059 |
