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recently rotenone has become the favored material. 
Pot ato aphid s . — There are only two aphids -that seriously attack 
potato plants. One of these, the green peach aphid, has been discussed. 
The other is the potato aphid ( Macrosiphum sol anif ol ii (Ashm. )), which, 
however, infests plants other than the potato. This species has been 
controlled \/ith nicotine since 1915, having been mentioned as so treated 
only in the United States and Canada, The best remedies up to 1934 were 
a spray consisting of nicotine sulfate and soap, 2- and 3-percent nicotine 
dusts, and a dust composed of tobacco powder and hydrated lime. 
Two other aphids infest potatoes, but they are unimportant, for 
each was mentioned only three times. The remedy for them was the same as 
given above. 
Pea aphid . —The pea aphid (Macrosiphum pisi (Kalt,)) has been treated 
in Canada and the United States with tobacco preparations since 1909, but 
not always successfully. Nicotine sulfate sprays and dusts were often 
recommended, and the most economical remedy seemed to "be a 3-percent nicotine 
dust applied to rows of peas with a tractor duster having a canvas trailer. 
Aph ids on oth er vegetables, — Ten other aphids on vegetables have 
been briefly discussed in the literature. Tobacco extracts controlled all 
of them — 3 species on sugar beet and lettuce in Europe, 2 each on tomatoes 
and celery in the United States, 1 each on beans and artichokes in the 
United States, and 1 on parsnips in Canada, 
Hop aphid , — This species, Phorodon humuli (Schr,), had been easily 
controlled since 1904 with nicotine because it is perhaps the most easily 
killed of all aphids. It was treated in the United States, Bohemia, 
Germany, Canada, and England, Against it were used tobacco decoctions, 
Black Leaf,' Black Leaf Dip, nicotine sulfate plus soap or flour paste, 5- 
percent Ivicodust, and 1-percent nicotine dust. The last seems to be the 
most frequently used in hop yards. 
A p ple grain aph id. — This insect, Rh opalosiphun prun ifo liae (Fitch), 
has been treated with nicotine in Canada and the United States since 1914, 
The best remedy was nicotine sulfate plus lime sulfur. 
Melon or cotton aphid,— This species, A phis gossypii Glov., attacks 
a wide variety of plants, but the abstracts mention only cotton, melons, 
cucumbers, gourds, and hibiscus, the first two being attacked the most 
seriously. It is widely distributed, and has been treated with nicotine, 
first in the United States, then later in Belgium, Nyasaland, Mexico, 
Chile, Canada, French West Africa, Bermuda, Peru, Russia, and Brazil. In 
1901 tobacco decoction, Rose Leaf, Skabcure Dip, and Nikoteen Punk v/ere 
used against .it, but since then Block Leaf, nicotine sulfate solution, free 
nicotines, and various tobacco-fumigating preparations have been used. 
Nicotine dusts were first tried against it in 1921 and since then they have 
gradually becomo more popular. In 1926 a 2-percent dust, applied at the 
rate of 35 to 40 pounds per acre on melons, was recommended, A dust com- 
posed of 94 parts of calcium arsenate and 6 parts of nicotine sulfate solu- 
tion (40-percent nicotine), applied at the rate of 3 or 9 pounds per acre of 
cotton, was recommended against the boll weevil (Anthonomus grandis Boh.) 
and this aphid. 
