October, ’18] 
BURRILL: NEW CLOVER PESTS 
421 
NEW ECONOMIC PESTS OF RED CLOVER 1 
By A. C. Burrill, Entomologist , Moscow, Idaho 
The third successive epidemic of the clover aphis (Aphis bakeri 
Cowen) 2 in Idaho in 1916 reduced considerably the seed yield in red 
clover, and also in white and alsike clovers. In one 40-acre irrigated 
field, which should have gone 10 bushels (some go 15 bushels) to the 
acre, the yield was 5 bushels to the acre, a loss of over $1,600. The 
average condition on some 60,000 acres throughout the State is esti¬ 
mated thus: 
Yield in Bushels per Acre 
Variety of Clover 3 1914 1915 1916 1917 
Red. 8 6 2-4 4-5 
Alsike. 7 7 6 ? 
White. 6 6 6 6 
In 1917, a January zero spell following after excessive numbers of 
aphis enemies, seems to have released the 1917 crop from excessive 
damage. 
Where the clover heads are very sticky from aphis, preliminary 
thorough drying is necessary before the seed will thresh. Usually 
the heat of the threshing melts the crystallized honeydew so that whole 
sacks may cake nearly solid. This phenomenon is also seen in the 
heap of weed seed sifted from the thresher separator. On first test, 
this sticky seed germinates better than well-dried unaffected seed. 
Idaho produces the best colored seed in the world and the best in price 
and yield per acre. Clover is no doubt the key crop in rotation with 
war wheat, and its enemies are thus of present importance. 
The enemies of this aphis are very numerous but their ability to 
check the epidemic seems to be nil until the third or fourth week in 
August, when the crop damage is almost complete. By that time the 
chaff and stems gather on the cutter blade of the mower, making de¬ 
lays for frequent cleaning advisable. The larval Coccinellids in the 
fields in August have bred out mostly Hippodamia 5-signata Kirby, 
H. convergens Guerin, H. lecontei Muls., and Coccinella trifasciata L., 
but they and their adults appear to be unable to penetrate all parts of 
the clover head to destroy every last aphis. And thus, a head may 
come to have as high as 300 aphids before enemies gain the upper hand, 
1 Published with the permission of the Director (J. S. Jones) Idaho Agr. Expt. Sta¬ 
tion. First presented as a paper at the Dec., 1916, meeting of the Am. Assn, of Econ. 
Entom., New York, N. Y., under the title “Insects of the Year in Idaho”; publication 
delayed for specific determinations. 
2 J. J. Davis, det. 
3 Id. A. E. S. Bui. No. 100. Clover Seed Production. L. C. Aicher. June, 1917. 
