UTAH ACADEMY OF SCIENCES 41 
SOME UNCOMMON PLANT PESTS. 
BY A. L. MATTHEWS. 
The work in the Salt Lake City War Gardens for the 
year of 1917 brought to light two pests, uncommon 
to the state of Utah, namely the Blackleg, (Bacillus 
phytophthorus) and the corn-root web worm, (Genus 
Crambus), A new pest which as far as can be deter- 
mined was discovered—the Tomato Aphis, possibly 
belonging to the Macrosiphum solanifolii. The dis- 
cussion of these pests will be treated in the order of 
importance relative to their destructive characteristics. 
BLACKLEG. (Bacillus phytophthorus). 
As nearly as can be determined Blackleg made its 
first appearance in America in an Idaho potato field, in 
1915. The cisease has spread rapidly since that date 
and was discovered for the first time in Utah in 1917, in 
connection with the Salt Lake City war gardens. 
Blackleg originated in Europe, reached its greatest 
development in Germany, and later it found its way into 
England. (Carruthers, W., Journ. Roy. Agr. Soc. Eng., 
68, p. 226-1907). The development of the disease in 
Germany was in connection with potato and the beet sugar 
farms. As far as is known at the present time, the Ger- 
mans have not found a remedy for the disease. The 
practice in England, where the disease is known, is to 
hold it in check by crop rotation. How the disease got 
into America is very much a matter of conjecture. 
Blackleg is a disease due to a bacterium called 
Bacillus phytophthorus. The disease affects differ- 
ent plants differently but all plants attacked show similar 
characteristics. A description of the disease on the 
potato will suffice to explain how the disease can be 
detected. When the potato is attacked with Blackleg 
the lower leaves wilt, turn slightly yellow, then brown 
and finally dry up and drop off the plant. The last leaves 
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