February, ’20] 
FELT: EUROPEAN CORN BORER 
63 
cornstalks. The state of Florida has laid a most sweeping embargo 
upon the shipment of plants or parts of plants from the infested area, 
while the Canadian government, by order of council, has prohibited 
the shipment into the Dominion of corn fodder or cornstalks from the 
infested area. 
The extension of Quarantine 36 to include the entire infested area 
has been seriously considered by the Federal Horticultural Board and 
owing to the uncertainties of the situation it has not, due in part at 
least to the difficulties in ascertaining the limits of the infested areas, 
been put in force. 
Economic Status 
There have been, during the last few months some statements 
voiced (9, 10) tending to indicate that the European corn borer may 
not prove to be an insect of much economic importance. These 
opinions appear to be based upon the fact that there was considerably 
less injury in the infested area in Massachusetts in 1919 than was true 
of some of the badly infested fields in 1918. Apparently little allow¬ 
ance has been made for the possible beneficial results following a 
general, though perhaps not entirely effective clean-up, for the activity 
of ephemeral and unreliable parasites, for the fact that seasonal dif¬ 
ferences may have been very unfavorable to the borer, and the obvious 
variations in the infested area. 
A general clean-up, even if a somewhat indifferent one, would result 
in the destruction of millions of borers and of itself should considerably 
lessen injury from the second brood. A well known, minute egg para¬ 
site, notably extremely variable in abundance from season to season, 
severely checked the borer. The development of the second brood 
injury in eastern Massachusetts was nearly a month later 1 in 1919. 
_ ~ • 
1 It may be significant that both the Blue Hill (mean 68.4°, departure from normal 
+ 1°) and the Concord (mean 68.3°, departure from normal 0°) Massachusetts records 
show a normal or a little higher than normal monthly mean temperatures for these 
stations in August, 1918, and decidedly subnormal records (mean 64.5°, departure 
from normal —2.9° and mean 65°, departure from normal —3.3° respectively) for 
the same month in 1919, a period of practically continuous development and growth 
for the second brood. Taking 43° F. as the critical temperature (it is probably 
higher for this season of the year) Blue Hills would have effective temperatures for 
August, 1918, amounting to 787.4, an increase of approximately 4 per cent above the 
normal and for August, 1919, effective temperatures of 666.5, a decrease below the 
normal of nearly 12 per cent, the total range between the two seasons for that month 
amounting to nearly 16 per cent of the normal effective temperatures. The Concord 
records show a normal (mean 68.3°, effective temperatures 784.3) for August, 1918, 
and a marked decrease (mean 65°, departure from normal —3.3°, effective tempera¬ 
tures 682) in 1919, amounting to more than 13 per cent of the effective temperatures. 
These figures justify expecting a retarded development, which latter was substan¬ 
tiated by field observations. 
