134 



Annals of Horticulture. 



insect enemy of the peach now found in the Burmuda islands, and thought 

 to have been brought there from the Mediterranean, where it has long been 

 known as an enemy of the orange and some other fruits. As it is figured 

 and described in the department report for 1890, it can hardly reach the 

 coast of Florida before being recognized and reported. To provide for bet- 

 ter facilities for this study of life histories, a building has just been erected 

 where temperature and other conditions can be controlled and the work 

 done more accurately. Experimental work with insecticides and apparatus 

 for applying them is carried on by special agents of the division in different 

 parts of the country, and the search for parasitic foes of injurious insects is 

 kept up both at home and abroad. The successful combating of the cot- 

 tony cushion-scale, in the orange-groves of California, by means of Vedalia 

 cardinalis introduced from Australia, has stimulated effort in this direction, 

 and several importations of parasitic insects have been made. One of 

 special interest to horticulturists is a reimportation of a European parasite 

 of the cabbage-worm, which has been successfully placed at Ames, Iowa, 

 and is reported to have become very abundant and to have greatly reduced 

 the number of cabbage-worms. An agent has also been sent to Australia to 

 investigate, and, if thought advisable, to import certain beneficial insects 

 likely to be valuable in California. 



' ' As is indicated by its name, the division of vegetable pathology devotes 

 its attention to diseases affecting plants. This is comparatively a new line 

 Depart- G f scientific work, and in consequence much attention is necessarily paid 

 Agricul^ to wor k of description and classification of fungi and bacteria affecting 

 ture. plants. When reports of new plant-diseases are received, specimens are se- 

 cured and a microscopic study is made to determine the cause of the disease 

 if possible. Usually this is done by growing the suspected germs in artifi- 

 cial culture media, such as sterilized gelatine or solutions selected for the 

 purpose. Inoculations are made on healthy plants with germs thus grown, 

 and if the diseased condition results, it is regarded as satisfactory proof that 

 the germ sought has been isolated. The life-history of the germ is then 

 studied to detect the period in its existence when it is most susceptible to at- 

 tack, and various remedies are tested in a small way until some are found 

 that are thought to be at the same time safe and efficient. These are then 

 tested on a larger scale under similar conditions, in regions where the dis- 

 ease is most disastrous, with a view to determining the most efficient of the 

 remedies tested, their comparative cost, and the best and most economical 

 means of applying. Results obtained are published from time to time, with 

 directions as to methods and means of application of the remedies. 

 These published results are sent to all persons who apply for them, or who 

 are known to be interested in the matter. The methods of preventing and 

 controlling black-rot and mildew in the grape are now so well-known that 

 they need not be mentioned here. Experiments on that subject have been 

 continued, however, during the present season, and it has been found that 

 much less copperas is required than was formerly used in Bordeaux mixture, 

 thereby reducing the cost of application from $14 per acre to $2 per acre. 

 The experiments on control of twig-blight in nursery stock, conducted at 

 Geneva, New York, during the season just passed, under the direction of one 

 of the assistants in this division, have been made on some three million 

 trees of cherry, apple, quince, pear, and other fruits in the nursery, and are 

 regarded as very satisfactory. Work on pear-blight, California vine disease, 



