PROGRESS REPORT OX THE EUROPEAN CORX BORER 51 
EFFECT OF INJURY TO CORN INTENDED FOR SEED 
It has been shown by Brown (9) that the mutilation of corn ker- 
nels does not necessarily prevent the production of normal plants by 
these mutilated kernels when used for seed, although the growth and 
yield of plants produced by such kernels may be less than from unin- 
jured seed. The proportion of " injured " kernels shown in Tables 
5 to 10 which could be used as seed, or as food, was very small, how- 
ever, and was more than counterbalanced by the rotting of adjacent 
uninjured kernels on the cob. caused by infection from the injured 
kernels (not shown on the records of grain injury). Moreover, the 
mutilation of the kernels by P. nubilolis, when such kernels were not 
completely destroyed, was usually confined to the seed coats and 
endosperms. According to Brown (.9) the injury to these portions 
of the kernels has a greater effect on the reduction of yield than injury 
to the germ. 
EFFECT OF STALK INJURY 
With respect to the stalk infestation and the consequent indirect 
injury and loss which such infestation causes to the ears and grain, 
it is difficult to assign any definite and uniform degree of economic 
importance to the figures pertaining to this factor as shown in the 
preceding tables, since the percentage of stalks infested, or broken 
over, does not in every instance have a distinct bearing upon the 
reduction in yield of grain or fodder. A high percentage of infested 
or broken-over stalks does not always mean severe damage to the ears 
and grain, because the principal injury and breaking over may occur 
late in the development of the plant, so that the grain may reach 
practically normal maturity in the case of field corn, or the ears 
of sweet corn may reach the roasting-ear stage before being seriously 
injured by the larvae. 
Definite relation between the percentage of infested stalks and the 
percentage of broken-over stalks seldom was found because the 
amount of breaking over, except in instances of very severe infesta- 
tion, depends to a considerable extent upon the size of the stalks of 
the variety attacked, and upon the occurrence of heavy wind or 
rainstorms after the injury takes place. Large heavy-stalked va- 
rieties will sometimes withstand considerable infestation without 
breaking over or showing an appreciable effect upon the ears or 
grain, whereas small-stalked varieties are much more susceptible 
to such injury as a result of the tunneling of the borers, and if 
severely attacked early in their development, extensive curtailment 
of grain production may result. 
EFFECT OF INJURY TO STALKS UPON THE NUMBER AND WEIGHT OF EARS 
In attempting to obtain information regarding the effect of stalk 
injury upon the number and weight of ears produced by such stalks, 
an important handicap has been encountered because of the fact 
that in fields where stalk infestation was severe enough to exert an 
appreciable effect upon ear production, noninfested stalks which 
could be used as a means of comparison were wanting. It is obvious 
that for satisfactory information on this point the infested and non- 
infested plants should be of the same variety and type, planted at 
the same time, and grown under identical soil and other cultural 
conditions. Therefore, it became necessary to make a comparative 
