PUBLIC RECORD OFFICE
Reference :-
TLC.O. 885
π l l l l l l l l l l
20 PUBLIC RECORD OFFICE, LONDON
126
Drugs, &c. :-
Tobacco.
Hops.
Opium.
Indigo.
Ginseng.
Capsicum.
Pepper and betel vine. Cardamoms.
Vegetable crops :-
Cucurbitaceæ.
Onion.
Carrot, &c.
Tomato. Asparagus. Egg-plant.
Permanent tree crops :-
Olive.
Mulberry. Coffee.
Tea.
Cacao.
Rubber, Castilloa.
Heoea.
Cinchona.
Kola.
Palms.
Fruit trees :-
Apple.
Pear.
Peach.
Kicksia.
Plum, &c.
Orange (including all citrus)
Mango.
Fig.
Guava.
127
(2) Pests which are liable to become epidemic or are not well established,
such as American gooseberry mildew, Hessian fly, &c. and
(3) Pests which are rare or recently discovered, such as pear thrips, tomato
canker, and crown gall, in England.
The division is, of course, artificial, and pests may pass from one category to the other in course of time.
In order to decide in which category the pests should be placed and to estimate their real economic importance, workers in each country should be invited, when making investigation for their own or for general information, to adopt a uniform plan, and the method suggested is as follows:
Not only should the life history be studied, as is, of course, done by all entomo- logists and mycologists, but the course of the disease be recorded as it affects the plant. Both the extent of the disease in each country and its intensity in each locality should be recorded on a scale (it is suggested) of five degrees. This system is in use by the Board of Agriculture for certain pests, and is based on the method adopted by the Meteorological Office for recording the prevalence or deficiency of rain, sunlight, and warmth in various districts of the United Kingdom, as com-- pared with the average in previous years. The method for plant diseases is, of course, slightly different. Theoretically, disease begins when the first insect or fungus spore attacks the host and ends with the death of the host; but in practice we may say it begins when the first sign of ill-health is noticed by a moderately expert investigator without the aid of a microscope and ends when the plant is economically of no value. At a stage half-way between these two points disease is general," above this point it is bad and very bad, below it is "slight" and "very slight." The very least degree is " a trace.". "By studying the course of an epidemic or serious disease, certain stages can be discovered which may be described as " very bad," "bad," general," "slight," very slight," respectively. Under this system, which is of course artificial, the Board has been able to say, not only in what districts of Great Britain American gooseberry mildew exists, but also in which places it is "bad," " general," or "slight." On a similar scale, reports are made as to the extent of disease on a given area, stating whether diseased plants are mány," many," common, few," or
very few." Somewhat similar results are being worked out as regards wart disease or black scab of potato. The Board is, therefore, able to say what parts of the country are affected and which parts are seriously attacked, and thus provide a correction of the alarmist reports which have appeared from time to time in the press. Most investigations into plant diseases show the area affected, but it is believed very few show the intensity of the attack. It is suggested that scientific workers throughout the Empire should be invited to work out a similar scale of the pests of their country and publish the results in the periodicals devoted to economic biology. [R.]
3) (6
13 4
27 64
very
Paragraph 13.-It is not suggested that special reports should be prepared for the survey in every case. In most cases the reports would be published in the Journal of Agriculture of the country in question; but these need tabulating after the manner of the Experiment Station Record. [R.]
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TO
Litchi.
Avocado pear. Hazelnut. Grape vine.
Banana.
Small fruits:-
Pineapple.
Cranberry.
Strawberry.
Raspberry.
Currant, &c.
Paragraph 11.-The survey which it is suggested should be made is a simple one and involves no additional labour. Probably every Government Entomologist and Mycologist is engaged in collecting information about the economic pests of the country in which he is working, giving special attention to those which are specially important. In England this work has largely been done by private persons or institutions and the information published in text-books such as those of Miss Ormerod, Mr. Theobald, Mr. Massee, and Mr. Cooke. Similar books have been published in other countries. It is suggested that these should be taken as a basis. The pests should then be divided into three classes :-
(1) Pests which are widely distributed and well established, taking as examples for England, woolly aphis, black currant mite, apple canker, apple scab;
Annexure 2 to No. 80.
REPORT ON THE FOREGOING MEMORANDUM BY THE SCIENTIFIC SECRETARY. The initiation of an adequate survey of the more important pests which attack cultivated crops throughout the British Empire, as suggested in the accompanying memorandum, would unquestionably be a work of great practical utility, and the task is one which might well be brought within the scope of this Committee's organisation.
Should such a course be adopted it would obviously involve the following altera- tions in our general procedure:—
(1) The extension of our organisation to all British Colonies and Possessions;
and
(2) The inclusion of fungi among the pests which we undertake to have deter-
mined and recorded.