1923 ENTOMOLOGICAL SOCIETY. 59 



CONTROL 

 Spraying 



Spray Material. The grape leaf-hopper nymph is very susceptible to 

 nicotine sprays, and is easily destroyed with as weak a dilution of nicotine 

 sulphate as 1-1600. Spraying experiments conducted during the past two years 

 with nicotine sulphate 1-1600 in combination with different materials, indicate 

 that the addition of lime, soap, kayso or bordeaux does not increase the efficiency 

 of the spray to any marked degree, at least it does not when the spraying is 

 done very thoroughly. However, in spite of this, we would not advise growers 

 to use nicotine sulphate alone. This year we urged them to combine the nicotine 

 with bordeaux mixture, and most of them did so. We believe that the bordeaux 

 more than paid for itself by checking to a greater or lesser extent fungus diseases, 

 and by stimulating the vines. 



Time of Application. With reference to the time when the hopper spray 

 should be applied, the usual recommendation in the past has been to spray 

 when the maximum number of nymphs are present and before many have trans- 

 formed to adults; or in other words, when the vast majority of the eggs have 

 hatched. It is not a particularly simple matter (as we found out from experience) 

 to ascertain when the majority of the eggs have hatched, in view of the fact 

 that the eggs are hidden within the leaf tissues. This year we decided that the 

 maximum number of nymphs were present by the end of the first week of July, at 

 which time a few first brood adults had commenced to appear in early graperies, 

 and we advised the growers to spray their vineyards the following week, July 

 10th to 15th. In all cases where the spraying was thoroughly done during the 

 second week of July, excellent commercial control was secured, but our exper- 

 ience indicates that spraying a week earlier, especially in the early sections, 

 would have been still more effective. Two badly infested graperies at Vineland 

 were thoroughly sprayed on July 3rd and 4th. At this time the most advanced 

 nymphs were on the point of changing from the 4th to the 5th instar. The 

 majority, however, were first and second instar nymphs. This spray destroyed 

 practically all the hoppers, and much to our surprise it also apparently destroyed 

 most of the eggs, because, although the eggs were hatching in large numbers 

 on adjoining vines, only an insignificant number hatched in the two early sprayed 

 graperies. In order to secure confirmatory data regarding the ovicidal value 

 of nicotine sulphate, we sprayed leaves on July 8th with nicotine sulphate, 

 (1) 1-1600, (2) 1-1200, (3) 1-800 and marked some other leaves as "checks." 

 In each experiment lime was added to the nicotine sulphate. On the leaves 

 sprayed with 1-1600 no eggs hatched for 11 days, and after that only 4.4 eggs 

 per leaf hatched. On the leaves sprayed with 1-200 and 1-800, 3.2 and 1.8 eggs 

 per leaf hatched respectively, but no nymphs appeared until 12 days after the 

 application. On the "check" leaves 88.2 eggs per leaf hatched. The evidence 

 secured from these tests and from the two early sprayed graperies that nicotine 

 sulphate destroys the eggs and that eggs on the point of hatching are most 

 susceptible, appears to us to be pretty conclusive, however, in order to secure 

 more positive information regarding this matter, we have planned to conduct 

 a series of experiments in the laboratory with definite numbers of eggs and with 

 eggs of known age. 



And now to come back to the question of when the leaf-hopper application 

 should be made, we are of the opinion that it should be put on when the most 

 advanced nymphs are in the fifth instar. In cases where it takes a week or longer 

 to spray the vines, spraying operations might well be started when the earliest 

 nymphs are in the fifth instar. Spraying at the time we recommend gives just 



