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THE ROSE LEAF-HOPPER.*
(Typhlocyba rosa L.)
F. H. LATHROP.
The ornamental value of rose plantings is frequently distinctly curtailed if not actually destroyed through the activities of the rose leaf-hopper. This has long been known as an important rose pest, and occurs almost wherever roses are grown in Europe as well as in America. The presence of the insect to an injurious extent is plainly indicated by the whitening of the foliage, and easily confirmed by finding the nymphs and their cast skins on the underside of the leaves.
In the late fall the eggs (Fig. 21) are deposited just beneath the bark of the mature stems, and it is in this stage that the insect passes the winter. About the middle of May, after the leaves have Fig. 21. - EGG OF ROSE LEAF become well developed, the eggs hatch and the tiny, white or pale yellowish nymphs emerge (Fig. 22). These lively little creatures at once migrate to the underside of the leaves where they may be found feeding, but where they are not likely to be observed unless special search is made for them. The nymphs continue to grow until the latter part of May when the skin is shed for the fifth and last time, and the adult insects appear (Fig. 23).
The adult is a rather slender, winged insect about three-sixteenths of an inch in length, and, like the nymph, is white or of a pale yellow color. The insect now becomes exceedingly active, dodging around the stems as one approaches, and flying swiftly away when the plants are disturbed.
There are at least two, and possibly three, broods produced during the course of the summer. The adults of the first brood, leaving the rose to a large extent, migrate to numerous other food plants where most of the nymphs of the later broods are produced.
NATURE OF INJURY.
By far the most serious injury to the rose is due to the disfiguring of the foliage as a result of feeding. The insects in both the adult and the immature stages feed by puncturing the tissues and sucking
Reprint of Circular No. 55, Vay 10, 1917
away the juices from the leaves (Plate XLVII). Each feeding puncture produces a minute white spot which is especially apparent on the upper surface of the leaf. The affected leaves soon become thickly stippled with these white spots, and when the infestation is
Fig. 22.-- NYMPHS OF FIRST, SECOND AND THIRD INSTARS.
heavy, the spots run together so that the entire surface of the leaf becomes pale (Plate XLVIII), and the plant as a whole presents a displeasing, sickly appearance. Plants which have the leaves severely injured in this way are unable to make normal growth.
While the crimson rambler seems to be especially susceptible to attack, many varieties of roses have been found to sustain severe injury, and no variety appears to be immune. Besides the rose, many other plants, including apple, cherry, and many small fruits are subject to injury from this pest.
The rose leaf-hopper, as is fortunately the case with most of our insect pests, is attacked by predaceous and parasitic enemies which under normal conditions greatly reduce its numbers. The adults may frequently be seen entangled in spider webs, while the nymphs as well as the adults fall prey to the small jumping spiders which inhabit the plants upon which the hoppers feed. Birds must also be a factor in this connection, in spite of the fact that these tiny, active insects do not seem to be very attractive food to many birds. Without doubt the most efficient of these destroyers to be observed in this locality is a minute parasitic insect that matures within the leaf-hopper egg, which consequently fails to develop.
Although parasites render valuable service in the control of this pest, it frequently becomes necessary to supplement their work with artificial control measures. If treated at the proper time, this leaf-hopper is not difficult to hold in check. Affected roses should be thoroly sprayed while the insects are in the nymphal stages, using a solution of nicotine and soap in the proportions of threefourths pint of nicotine sulphate and five pounds of soap to one hundred gallons of water. Where only a few plants are to be treated, the mixture may be prepared at the rate of one teaspoon level full (four cubic centimeters) of nicotine sulphate, 40 per ct., and two ounces of soap to one gallon of water. The spray is effective only while the insect is in the immature stages, for the adults fly so quickly that they cannot be reached with the spray. It will be seen from the life history that the treatment may be effectively made from the time of hatching until the last of May in this locality. It is advisable, however, to make the application as soon after hatching as possible, for at this time the nymphs are more easily killed, and they will be destroyed before the foliage has been damaged. As has already been stated, the later broods are not as a rule so
If they should become destructive, however, the nymphs may be destroyed by repeating the treatment just described.
numerous on roses.
Department of Horticulture.
U. P. HEDRICK, Horticulturist.
Roy D. ANTHONY, Associate Horticulturist.
GEO. H. HOWE, Assistant Horticulturist.
J. W. WELLINGTON, Assistant Horticulturist.
O. M. TAYLOR, Foreman.
FRED E. GLADWIN, Associate Horticulturist.
(Connected with Grape Culture Investigations.)
TABLE OF CONTENTS.
I. Vinifera grapes in New York.
V. Orchards: Location and care.
VI. Culture of field beans.