PLANT DISEASES

Evening Post, Volume CXVII, Issue 18, 21 July 1934, Page 5

PLANT DISEASES

RESEARCH IX ENGLAND

RHODODENDRON PEST

(From'"The Post's" Representative.) LONDON, May 31.

At the' Horticultural Society's great spring show at Chelsea one has an opportunity of learning something of what.is being done in botanical research in this country. Institutions which are devoted to plant research are the Horticultural College, Swanlcy, Kent; the Imperial College of Science and Technology, South Kensington; the Potato Virus Eesearch Station, Cambridge; the Kothamsted Experimental Station; the Seale-Hayne Agricultural College, Newton Abbot, Devon; and tlio Boyal Horticultural Society's Garden, Wisley, Surrey. Wisley, situated in the middle of one of the ancient forests of England, was chosen for its unproductive soil, experimental manuring thus being influenced to a minimum extent by the original nature of the soil. The.studies there arc divided into three departments—Physiology,. Entomology, and Mycology. Research work goes on under these three headings, and students receive a two years' intensive course. A NEW WHITE JIOT. A subject that has occupied a good deal of . attention lately is the new minute white fly which has attacked the rhododendrons of this country. It was first noticed in 1928 and appeared to be the fly which attacks the tomato plants. Investigation proved, however, that it was apparently new to this country, and there is no available record in other countries of its existence. It has been given the name of Dialeufodes Chittendeni, after the late director of Wisloy. The eggs are laid on the under side of the rhododendron leaf and in due course the larvae cover the leaf. An oil emulsion with nicotine' rubbed on the leaves destroys the larvae, and this is the treatment that has been suggested and used. . The south-west of England has been seriously affected by the fly, and plants sent from this area to other parts have carried the blight. . Another disease that is being watched is the virus disease of tlie narcissi. This streaks the leaves. The most powerful microscope is not able to make the germ visible. Nevertheless, the germ* can be transferred by contact of two plants or by a needle injection. So far the only remedy suggested is the burning of all affected stock. , .

Other work going on at Wisley includes the classification of bearded iris plants, of which there are now 900 varieties at Wisley; the investigation, of rust •on antirrhinums, a disease which caused a lot of trouble last year; study of iris "scorch" which has not yet been fully investigated; and the influence of soil conditions on certain common garden plants. ' HOT WATER TREATMENT. .The Seale-Hayne AgricultufaL College in Devon is also carrying on work over a wide field; Narcissus flies, stripe disease of narcissus,' and hot water treatment for these occupy their attention. Potato sickness associated with the eel worm is being investigated and experiments with the hot water treatment have • proved very satisfactory. Much trouble has been caused in the south-west of England by the eel worm pest iiv violets. The hot water treatment has. also; been, applied in this case with not altogether satisfactory results. . Tho series of runners treated for thirty minutes at 110 degrees P.- were the ' only plants which remained healthy. Eel worm affected runners stood the' hot water treatment very badly, but healthy runners grew well. In both cases much of the older leaf was destroyed, but young leaves soon grew in their'places. 'Fungal diseases in all types of vegetables are also investigated. . : :

Tho College at Swanley staged an exhibit showing damage done to decorative plants by thrips,. and.the Cambridge Potato Virus Eesearch Station staged a comprehensive exhibit of p'o 7 tato plants affected with virus diseases while tho Rothamsted Station illustrated the methods used. for. estimating insect populations, yand the means of avoiding epidemics of insect pests'. Some apparatus was also shown which is used for" determining the attractiveness of. plants to insects; : ■ ■