. Control of roundheaded apple tree borer. Apple-tree borers. 4 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 40 near Godfrey in 1938 and 1939, starting with strengths thought necessary to kill the larvae and continuing down through lower dilutions as injury to the tree developed. Table 2 summarizes the data obtained. From these tests we concluded that although ethylene dichloride is very effective in killing borers in apple when used at strengths of 10 to 50 per cent, any strength sufficient to give a good kill of borers will injure the apple trees. Later Tests During the years 1939, 1940 and 1941
. Control of roundheaded apple tree borer. Apple-tree borers. 4 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 40 near Godfrey in 1938 and 1939, starting with strengths thought necessary to kill the larvae and continuing down through lower dilutions as injury to the tree developed. Table 2 summarizes the data obtained. From these tests we concluded that although ethylene dichloride is very effective in killing borers in apple when used at strengths of 10 to 50 per cent, any strength sufficient to give a good kill of borers will injure the apple trees. Later Tests During the years 1939, 1940 and 1941, we tested three treat- ments in three orchards, as follows: Treatment 1: 20 per cent strength of carbon bisulfide, in a fish oil soap emulsion, one-half pint applied per tree, tree mounded. Treatment 2: PDB in Dendrol, one-half pint applied, fig. 5, per tree (2 pounds PDB in 1 gallon Dendrol, made up to 2 gallons with water), tree mounded, fig. 6. Treatment 3: Carbon bisulfide (unemulsified), injected into insect burrows from oil can, fig. 3, tree not mounded but trowel full of earth placed over each treated spot. Treatment 4: Check, no Fig. 3.—Oil-can method of injecting carbon bisulfide into burrow of the roundheaded apple tree borer. The location of the burrow near the base of the tree is indicated bv whitish or brown Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Chandler, Stewart Curtis, 1889-; Flint, W. P. (Wesley Pillsbury), 1882-1943. Urbana
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