1058 DISEASES AND INSECTS 



DISEASES AND INSECTS 



1326. Apple cluster ready for the spray. 

 The blossoms have not yet opened. 



substances that had an injurious effect on the body 

 of the insect. These were of two kinds, mainly: in- 

 fusions which were astringent, and caustic substances 

 which burned the tissues. Tobacco water and alkaline 

 washes have been used for many years. One of the 



first poisons to 

 be used was 

 white helle- 

 bore. The em- 

 ployment of 

 arsenical poi- 

 sons may be 

 said to belong 

 to America, 

 and even at the 

 present time 

 has small place 

 in the economy 

 of fruit-grow- 

 ing in Europe. 

 The wide- 

 spread use of 

 arsenical poi- 

 sons is largely 



due to the influence of the incursion of the potato-bug. 

 There are no reliable records which give us the exact 

 date of the first use of paris green. It probably 

 occurred about 1865 or 1866. However, towards 1870 

 paris green was used very generally throughout the 

 western region in which the potato-bug first appeared. 

 At this time it was applied almost exclusively in the 

 dry form diluted with gypsum or flour. From potato 

 to cotton, tobacco and finally to fruit trees, is the de- 

 velopment of this poison for destroying leaf-eating 

 insects. So far as records are available, it appears that 

 fruit trees were first sprayed with paris green between 

 1873 and 1875. Among pioneer sprayers, should be 

 mentioned the names of C. V. Riley, United States 

 Entomologist; LeBarron, State Entomologist of Illi- 

 nois; William Saunders, London, Ontario, Can.; J. S. 

 Woodward, Lockport, N. Y.; T. G. Yeomans & Sons, 

 Walworth, N. Y.; A. J. Cook, Agricultural College, 

 Mich. 



Following paris green came london purple, then 

 white arsenic, and later arsenate of lead. Since that 

 time many different forms of arsenical poisons have 

 been compounded, offered to the public and frequently 

 used. A few years ago paris green was used extensively, 

 but its popularity now is decreasing, prob- 

 ably because it contains a large percentage 

 of soluble arsenic, which increases the 

 danger of foliage injury. London purple 

 has been largely dropped by fruit-growers, 

 owing to its variable quality. White 

 arsenic, in combination with soda and 

 with lime, forms a reliable insecticide and 

 is used by some growers, especially those 

 who make a practice of preparing the 

 home-made solutions. Arsenate of lead is 

 the insecticide used most widely by the 

 growers at the present time. It possesses 

 several advantages, the more important 

 of which are a small percentage of soluble 

 arsenic and better sticking qualities. 



The sucking insects presented a more 

 difficult problem of control than the biting 

 insects, and a longer time elapsed before 

 effective methods had been devised for 

 treatment. One of the first efficient sprays 

 for these insects was kerosene in the 

 form of a soap-and-water emulsion, which 

 .. 7 ,, was recommended by Riley and Hub- 



bard. Among the earlier sprays for these 



miscible oils were introduced. These proved to be very 

 effective and are still used. The most important step 

 in the control of the sucking insects is marked by the 

 introduction of the lime-sulfur wash. This mixture, 

 which was originally developed as a dip for the control 

 of scab on sheep, was 

 first used as an insecti- 

 cide on fruit trees in 

 1886 by F. Dusey, of 

 Fresno, California. The 

 wash proved very effi- 

 cient and with modifica- 

 tions came quickly into 

 favor. Now lime-sulfur 

 is the leading insecticide 

 for the control of certain 

 scale insects and also, in 

 a more dilute form, the 

 leading fungicide for 

 the more troublesome 

 diseases of the apple. 



The treatment of fun- 

 gous diseases of plants 

 by liquid applications 

 began with the dis- 

 covery of bordeaux 

 mixture. Early in the 1880's, diseases of grape-vines 

 threatened the extinction of French vineyards. The 

 situation engaged the attention of French investiga- 

 tors. Notable among them were A. Millardet and his 

 co-workers of the Academy of Science, Bordeaux, 

 France. He, with others, discovered partly by accident 

 and partly by experiment that solutions of copper 

 prevented the development of downy mildew. After 

 much experimentation, "bouillie Bordellaise" was 

 found to be effective in preventing the growth of 

 downy mildew and other plant parasites infesting the 

 grape in that region. The announcement was definitely 

 made in 1885. The following year the European 

 formula for bordeaux mixture was published in several 



E laces in the United States, and immediately there 

 egan an unparalleled period of activity in economic 

 vegetable pathology. This mixture, though somewhat 

 modified and developed, continues to be a leading 

 fungicide. The value of lime-sulfur as a fungicide 

 applied to the peach during the dormant season to 

 control the leaf-curl has been recognized. About 1907, 



1328. A bucket pump. 



broom for ap- 

 plying spray. 

 An early de- 

 vice. 



insects was also tobacco 

 soaps, both of which 



and whale-oil 



. , are used rather 



widely at the present time. Later the 



1329. Knapsack pump. 



Cordley discovered that lime-sulfur in more dilute 

 form may be applied to the apple and some other 

 tree fruits in foliage without danger of foliage injury, 

 and that in addition to being as effective as bordeaux 

 it produces no spray injury on the fruit. Since then 

 lime-sulfur as a fungicide has practically replaced 

 bordeaux in the case of those fruits for which it can 

 be used on the foliage with safety. The self -boiled 

 lime-sulfur was developed about 1907 as a fungicide 

 for the control of the brown rot of the peach. 



