February, ’24] 
WEBSTER: INSECT CROP DAMAGE 
55 
moisture 12.1%; excessive moisture, 2.4% frost or freeze, 3.8%; hot 
winds, 2.2%; plant disease, 3.2%; insects 2.5%. These figures are 
obtained from estimates made by a large number of volunteer crop 
reporters over the country. 
It is interesting to note that for both plant diseases and insects, the 
losses seem to be increasing in the later years for which estimates are 
given. This is likely to be due to a more adequate recognition of the 
real losses occasioned by these two factors, rather than to an actual 
increase in those losses. 
Estimates of Damage by Insects 
In entomological text books and in other articles regarding insect 
damage to crops, it is common to estimate that not less than 10% of the 
wheat crop is lost because of insect attack. There is a wide gap be¬ 
tween estimates from these two different sources. Some of the reasons 
for this difference are brought out in this paper. 
Much Damage not Easily Recognized 
Damage to crops by large insects, such as grasshoppers, is readily 
observed. But much damage by insects to the small grains is insidious 
in nature. Many of the insects concerned are hidden within the plant 
tissue; some of them in fact spend the greater portion of their life be¬ 
neath the surface of the ground. Often a large share of the crop may be 
infested with the Hessian fly, or by the wheat stem saw fly, with little 
evidence of such infestation that is externally visible. The total amount 
of the damage to crops usually is not appreciated because it is not 
clearly evident. 
Where severe outbreaks of any insect occur, the damage is so con¬ 
spicuous that its economic importance is recognized at once. But there 
is in addition a certain amount of damage by insects every year in any 
locality. As Folsom remarked in his classic study of the insects affecting 
red clover in Illinois, there is a constant drain on the plant thru attack 
by insects, unnoticed because it occurs every year. Losses of this 
nature probably are never taken into account in crop estimates. 
Potential Damage 
Moreover, a portion of the damage by insects is potential. A wheat 
field may be heavily infested with the Hessian fly or the wheat stem 
sawfiy before cutting, yet suffer only a moderate amount of loss on 
account of lodging, if there are favorable weather conditions before 
