26 THE REPORT OF THE No. 33 



1-1,200 in combination with lime will destroy the eggs in all stages of develop- 

 ment, and that this strength of nicotine is 100 per cent, effective. 



Having satisfactory evidence that the eggs are as readily destroyed as the 

 nymphs, our next step was to ascertain when the leaf hopper spray may be 

 applied to best advantage. With this object in view, three infested blocks 

 of grape vines at Barnesdale, St. Catharines, were sprayed at different times 

 with nicotine sulphate i}/i pint — 100 gals.) and Bordeaux mixture. The first 

 block was sprayed on July 6th, about eight days after Concord blossoms fell, 

 and the other two blocks were treated on the 13th and 20th respectively. The 

 spray mixture was applied by means of a triplex Bean outfit, with two short 

 rods and angle nozzles, and pains were taken to thoroughly wet the undersides 

 of the leaves. The results* secured from this experiment were very gratifying 

 — in the three blocks the leaf hopper was reduced to negligible proportions. 

 Even in late summer only odd leaf hoppers could be found on the vines, and 

 the foliage remained green all season, whereas, in the "check" grapery, the 

 foliage showed severe leaf hopper injury from early August to the end of the 

 season. 



The majority of Niagara grape growers with infested vineyards sprayed 

 their vines as recommended by us during the period July 11th to the 21st, and 

 in all cases where the work was done properly the hopper was reduced to insig- 

 nificant numbers. At Barnesdale, for example, where there are some seventy 

 acres in grapes, and where conditions, in the form of bush-land adjoining the 

 vineyards, are particularly favourable for leaf hopper, early and thorough 

 spraying almost completely eradicated the insect. 



From our experience in combating this insect during the past two years 

 we have learned several things of importance, viz. : 



(1) That it is inadvisable to postpone spraying until the majority of the 

 eggs have hatched, because this permits too many of the nymphs to transform 

 to the adult stage. 



(2) That as hopper eggs are susceptible to nicotine, the spray may be applied 

 shortly after the overwintering adults cease egg-laying. Our observations indicate 

 that egg-laying ceases about the time Concord grape blossoms drop, so that, 

 allowing a safety margin of several days, spraying operations may be commenced 

 about one week after the fruit sets. 



(3) That there is a period of at least two weeks when very effective work 

 can be done (1923 — July 6th to 21st). The fact that there is a considerable 

 amount of latitude as to when the application may be put on, makes it possible, 

 in sections where the root worm is a serious pest, to kill two birds with the one 

 stone by combining the nicotine with one of the root worm sprays, thus saving 

 the time and labour of a special application. Likewise, in vineyards infested 

 with the grape berry moth, the leaf hopper spray can be made to coincide with 

 the second application for the moth. 



(4) That, in addition to those mentioned above, the "egg-spray" (applied 

 after cessation of egg-laying) has the following advantages over the "nymph 

 spray" (applied when the vast majority of the eggs have hatched) : it practically 

 eliminates the second brood ; it lessens the danger of staining the fruit with 

 Bordeaux mixture; it is usually of more value in checking plant diseases; it 

 simplifies spraying operations, and saves material, because it is put on before 

 the heavy new growth is made. 



* We had planned, as suggested by Mr. Van Dine, Pennsylvania State College, to present 

 the results in the form of brix readings of grape juice, but we were unable to do this because 

 a severe hail storm on August 24th seriously injured the crop in our experimental plots. 



