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Table III will show that only one of the affected clusters retained fruits throughout the season. This cluster was infested late in the season, and did not suffer such severe injury as would have been caused by an earlier infestation.
TEST WITH LIME-SULPHUR AND NICOTINE SOLUTION.
This test was conducted in an orchard of mixed varieties of apples, containing about one hundred and seventy-six trees, of which one-third or more were of the variety Rome. The latter are twentyone years old and, because of their size, as well as susceptibility to the rosy aphis, lend themselves well to the proposed experiment.
PLAN OF EXPERIMENT.
In planning the test the chief object was to determine the effects of lime-sulphur and nicotine solution against the newly-hatched nymphs of the rosy aphis.. Plats were provided as follows: Plat I. Nicotine solution (40 per ct.) three-fourths of a pint to one hundred gallons
of lime-sulphur solution, 1 to 8, applied as a delayed dormant treatment. Plat II. Check.
The trees in Plat I, rows 1 to 5 inclusive, Fig. 10, were treated with nicotine solution combined with lime-sulphur on May 1, when leaves of the most advanced buds were projecting as much as one-fourth to half an inch. The spraying was purposely delayed until the eggs had begun to hatch and it was reasonably certain that most of the nymphs had emerged. As in all of our experiments against this pest the mixture was applied in liberal quantities and no tree was considered properly sprayed until every bud was wetted with the liquid. In this operation an average of eleven gallons of material was applied to each tree.
RESULTS OF SPRAYING ON APHIDES AND TREES.
Unlike last season's experience, avence was very scarce in the experimental plats and the occasional specimens that were observed were discovered only by careful searching. During the earlier part of the season sorbi was the dominant species, and it was not especially difficult to find at least one, and occasionally three or more of the nymphs on some of the buds. The injury to the crop was largely if not entirely the result of attacks by this species. The associated form, pomi, became abundant during June and many of the tips of the new growth were abundantly infested with the species, while fruit clusters were exempt from injury. On June 30, when sorbi
11 10 9 9 8 7 6 5 4 3
* Check, Plat 2. Sprayed, Plat 1, rows 1 to 5.
Fig. 10.- DIAGRAM OF ORCHARD SHOWING SPRAYED AND CHECK TREES.
had ceased breeding on the apples and the migrants had largely left the orchard, each plat was carefully examined to note the number of affected fruits. The data are tabulated in Table IX.
TABLE IX.- RESULTS OF SPRAYING AGAINST Rosy APHIS.
NUMBER OF DIFFERENT SECTIONS AFFECTED.
Centers Fruits of in
Leaves infesta- | jured. curled.
Rome. Husband. Rome. Axident. Rome. Hanlon. Rome.
0 0 0 0
X.. Rome.. Rome.
0 0 0
0 0 0 0 0 0
X... Rome.. Florence Rome. X.... Rome, Wagener Rome. Kinnaird. Rome, Rome. Kinnaird.. Rome. Hubbardston. Rome.. Hubbardston. Rome. Wagener Rome,
Lime-sulphur and nicotine.
0 0 0 0 0
1 - 1 1- 2 1-3
1 6 1- 7 1- 8 1-9 1-10 1-11 2- 1 2- 2 2-3 2 4. 2 5 2- 6 22 8 2- 9 2—10 2-11 3— 1 3-2 3— 3 3 4 3— 5 3- 6 3 7 3-8 39 3-10 3-11 4 1 4- 2 4 3 4 4
o Dead tree.
TABLE IX.- RESULTS OF SPRAYING AGAINST Rosy APHIS (concluded).
* Purposely left unsprayed for comparison with Tree 6, row 5. x Small tree.
DISCUSSION OF RESULTS.
Previous to the initiation of our studies knowledge on the early activities of the rosy aphis was very meagre. Particularly was this true regarding the period when the species hatches and seeks the opening buds. This lack of information was largely due to the fact that the newly-hatched nymph was not known and was therefore unrecognizable from those of the associated species of aphides. Since the nymph of the first instar of sorbi has been discovered and is now distinctly differentiated from other forms, it has been possible to follow its activities quite closely; and both observations and experimental tests showed that as far as this orchard is concerned hatching was concluded on or a little before April 30. At this time the leaves of the most advanced blossom buds were projecting as much as half an inch.
The susceptibility of the rosy aphis to the delayed dormant application of lime-sulphur and nicotine solution is plainly indicated. Rarely in experiments with common orchard insects do sharper contrasts appear than existed between Plats I and II, with respect to this species. Altho the infestation was not large, the trees in Plat I were practically exempt from injuries either to the fruit or foliage, a condition quite different from that which existed in Plat II. While it is desirable to repeat these tests over a period of several years before drawing final conclusions, these results certainly border on the line of conclusive demonstration and are very convincing, especially when considered in the light of the data obtained in similar experiments during the preceding year.
AUXILIARY EXPERIMENTS DURING 1916.
Thru the courtesy of Commissioner Charles S. Wilson the auxiliary experiments were conducted with the assistance of Mr. L. F. Strickland, Inspector of the State Bureau of Horticulture for Niagara County, and Mr. A. B. Buchholz, Horticultural Inspector for Orleans County.
EXPERIMENTS IN NIAGARA COUNTY.
Test 1. Orchard of E. S. Gifford, Gasport.- In this planting thirty trees of the variety Greening, about sixty-one years old, were reserved for the test. On April 26, as the buds were green at the tips and occasional young leaves were expanded, the trees were sprayed with lime-sulphur in combination with nicotine sulphate (Black Leaf 40) in the usual proportions. In order to insure thoro treatment the trees were drenched with the spraying mixture, using on an average twenty-five gallons of the liquid to the tree.
Rosy and oat aphides were the more abundant species on the trees, the infestation of which was variable, averaging from one to seventeen of the insects to each bud. On May 12 and 13 the aphides were decidedly more abundant on the unsprayed Greenings. An examination of the unsprayed trees on June 21 showed that a considerable number of the fruit and leaf clusters had been injured