JOINTWORM FLIES. 25 
cates that there is small hope of destroying the joint worm by passing 
infested straw through the manure pile. 
The writer has been experimenting for the past three years in 
plowing under wheat stubble for the purpose of observing the 
effect on infestation the following year in wheat planted on the same 
ground. This work was done in the vicinity of Charlottesville, 
Va., where no infestation occurred nearer than 5 or 6 miles. There- 
fore the data secured should be reliable, as there was no opportunity 
for the jointworm to come in from neighboring fields. Small plats 
were used and the infestation was accomplished by bringing in a 
very large amount of infested stubble from a distance, placing it in 
the growing wheat, and allowing the adults to emerge and infest 
the plat. In order to insure heavy infestation, large amounts of 
badly infested stubble were brought in again from a distance after 
the wheat was cut, making accurate counts of the number thus 
brought in, and then carefully estimating the infestation that already 
existed on the plat. The total number of wheat stems or stubbles 
was then counted on several representative square yards of the plat. 
In this way the percentage of artifical infestation could be deter- 
mined accurately. The infested stubbles which had been introduced, 
together with the stubbles already standing on the plat, were then 
turned under. The ground was plowed as soon after harvest as 
possible, disked, and some crop like peas or soy beans sown. The 
plat was disked again in the fall at the proper time and reseeded to 
wheat. In this way an 8 per cent infestation was reduced to 1 per 
cent the following year. A second trial reduced the infestation from 
. 32 per cent to 3 per cent. A third trial in 1918 reduced a 19 per 
cent infestation to 2 per cent. 
These experiments indicate that plowing under stubble is a very 
effective remedy. It doubtless would destroy all of the insects if 
all of the infested stubbles could be completely buried, but it is im- 
possible to do this. Nevertheless it is practicable to control the 
ravages of the species in this manner. While this method of con- 
trol would necessitate a change in the existing rotation of crops 
where wheat is used as a nurse crop for clover, it would seem that it 
should be adopted if millions of dollars could be saved every year 
in this manner. Some agronomists admit that it would be prac- 
ticable to change the existing system of rotation so as to permit 
plowing down stubble to suppress important insect pests. If this 
were done not only the jointworm but also the Hessian fly would 
be controlled, and thus two of the major insect pests of wheat would 
be largely shorn of their power for harm to our most valuable bread 
grain. 
