152 EXPERIMENT STATION RECORD. 



Papers on deciduous fruit insects and insecticides. — Spraying experiments 

 against the grape leafhopper in the Lake Erie Valley, F. Johnson ( U. S. 

 Dcpt. Agr., Bur. Ent. Bui. 97, pt. I, pp. 12, pis. 2, figs. 5). — In the A'ineyards of 

 the Lake Erie Valley serious depredations by this pest are i.isnally confined to 

 somewhat limited areas adjacent to rough lands and woodlots. Periodically, 

 however, some as yet unknown conditions seem to favor its multiplication and 

 it spreads over wide areas, causing injury amounting to many tliousands of 

 dollars. During the seasons of 1001 and 1902 many hundreds of acres of vine- 

 yards in the vicinity of Westfield, Cliatanqua County, N. Y., were seriously 

 injured by the pest, but in 190.S it disapi>eared to a considerable extent and 

 serious injury was again confined to limited areas until the season of 1010. 

 The author states that the insect is now on the increase and that during the 

 summer of 1910 it spread through large blocks of vineyard, and toward the 

 latter end of the summer its presence in more or less destructive numbers was 

 evident throughout the entire grape belt. 



" The adults and nymphs of the grape leafhopper feed upon the underside of 

 the grape leaf and by sucking the juices therefrom cause it to take on a yellow- 

 ish, mottled appearance which later turns brown, and where the infestation is 

 heavy the leaves dry out and become functionless before the fruit is mature." 

 The adult, in which stage the winter is passed, leaves its winter protection as 

 the days become warmer in early May and commences to feed upon the new 

 growth of almost any plant with which it comes in contact, showing some pref- 

 erence, however, for the foliage of bush fruits, such as wild blackberries, culti- 

 vated raspberries, and strawberries. With the unfolding of the leaves, there 

 is a general migration back to the foliage of the grapevine, this being the only 

 plant upon which this particular species of leafhopper is known to reproduce. 



In the vineyards of the Lake Erie Valley egg laying by overwintering females 

 does not commence until about June 1, or after the adults have been feeding 

 upon the vines for several weeks. The eggs, which are deposited on the under- 

 side of the leaves, are tucked under the skin indiscriminately as to location. 

 " The egg stage covers a period of about 10 days to 2 weeks. The period of 

 egg deposition is obviously a long one, since newly emerged nymphs are present 

 upon the foliage from the middle of June until late in October. Observations 

 indicate, however, that the maximum deposition must occur during the last 3 

 weeks in June and the first week in July, since the period when there is a 

 maximum number of nymphs upon the leaves is included in a period from the 

 last week in June until about August 1, at which latter date many fully devel- 

 oped nymphs are making their final molt." 



The nymphs commence to appear about the middle of June. Five molts take 

 place, the first 4 requiring a period of 5 days for each, while between the fourth 

 and fifth, there is a period of 12 days ; thus about a month is required in which 

 to complete the nymphal period. The widespread dissemination of this pest 

 is thought to take place largely during the fall migration and again during the 

 spring migration when the adults leave their winter shelter and return to the 

 vines. 



On account of the inability of the nymphs to escape from the underside of 

 the grape leaves, and because of the soft and unprotected condition of their 

 bodies, the nymphal period is the most vulnerable stage of the insect. In ob- 

 servations made during the summer of 1910, the date on which the maximum 

 number of nymphs was found to be present on the foliage before those earliest 

 to hatch had developed their wings and before serious injury had become ap- 

 parent was July 12. At this time a small number of the nymphs earliest to 

 hatch had entered upon their last molt and the number present upon the leaves 

 in earlier stages of development was very large. 



