June, '23 
haseman: arsenic, calyx cups and codling moth 
271 
which the worms consumed. These experiments show that for third instar apple 
worms and older ones, the lethal dosage is approximately five ten thousandths 
(.0005) of a gram of powdered arsenate of lead. This is practically the same as the 
average calyx cup content (.000521 grams) as shown from numerous orchard spray 
tests. It seems certain therefore that in good orchard spraying the lower calyx cup 
of each blossom hit squarely with the “Calyx Spray” will receive sufficient arsenic 
to poison the small apple worms which may attempt to enter the fruit at that point. 
The writer began this study in 1909 under the direction of the late 
Professor Slingerland and continued it in 1910 under Professor Herrick. 
The original purpose was to determine what pressure and what type of 
nozzle placed the greatest amount of arsenical down in the calyx cups 
as protection against the later entrance of calyx worms. The first 
spray tests were made in the Farm Engineering Laboratory, Cornell 
University, where Professor Riley prepared special equipment to main¬ 
tain absolutely constant pressures with each nozzle. The chemical 
analyses were made by Professor Cavenaugh of the Agricultural Chemis¬ 
try Department. 
On returning to the University of Missouri, the writer went into the 
orchard with the experiment in actual spray tests. As new or improved 
nozzles were brought out they were included in the tests. Except for a 
few years when frosts or funds prevented, the experiments have been 
repeated in the experiment station orchard at Columbia, Missouri each 
year since 1910. As the work progressed the original purpose of the 
study was expanded to include an accurate determination of the actual 
quantity of arsenic placed in each cup by each nozzle, and pressure used. 
Then the question arose, is this quantity sufficient to actually kill the 
codling moth larvae of different ages or sizes. This called for a labora¬ 
tory test to determine the lethal dosage for apple worms. All chemical 
analyses have been made by members of the Agricultural Chemistry 
Department. 
Plan of Procedure 
Each year a block of apple trees including one or some seasons two 
standard Missouri varieties, Jonathan, Ben Davis and Missouri Pippin, 
has been set aside for these tests. These trees receive the first spring or 
clusterbud spray just the same as the rest of the orchard. When 
conditions are right for the calyx spray the experimental trees are 
sprayed by an experienced orchard man, being given a thorough treat¬ 
ment with the standard spray solution including one pound dry arsenate 
of lead and one and one-half gallons liquid lime sulfur in fifty gallons 
of water. A power sprayer maintaining reasonably constant pressures 
