64 DECIDUOUS FRUIT INSECTS AXD INSECTICIDES. 



Commercial tobacco extracts (blackleaf tobacco extract, contain- 

 ing 2 1 2 c - per cent nicotine sulphate) applied at a dilution of 1 to 

 150 gallons of water, or a still more highly concentrated form 

 ("blackleaf 40." containing 40 per cent nicotine sulphate) applied 

 at a dilution of 1 to 1,500 gallons of water, may be used with arsenate 

 of lead. The tobacco extract is used on the leaf as a contact remedy 

 against the nymphs of the grape leafhopper and the arsenate of lead 

 on the fruit against the larvae of the grape-berry moth. Paris green 

 and arsenite of lime should not be mixed with the tobacco extracts 

 as a substitute for arsenate of lead, for serious foliage injury results 

 from these combinations. 



The combination-spray application against these two insects 

 should be made by the "trailer'' method, as shown in Plate VIII, 

 figure 2. The nymphs of the grape leafhopper suck the juice from 

 the underside of the grape leaves and are killed by the tobacco 

 extracts coming in contact with their bodies; hence, in making this 

 application to the underside of the grape foliage most of the grape 

 clusters are drenched by the spray. By the addition of arsenate of 

 lead this application may also act as a treatment against the larvae 

 of the grape-berry moth. 



Since no serious infections of black rot have occurred in the vine- 

 yards of the Lake Erie Valley during the past few seasons, the stronger 

 fungicide formula does not appear to be necessary. Hence the 

 combination spray formula recommended against this pest is as 

 follows : 



Lime 1 [pounds. . 3 



Copper sulphate ^Bordeaux formula \ . -do 3 



Water J [gallons. . . 50 



Arsenate of lead (insecticide) pounds . . 3 



Since the effectiveness of an arsenical spray treatment depends 

 upon the presence of the poison upon the blossom clusters and upon 

 the berries when the larva? hatch from the eggs and commence to 

 feed upon the blossom buds and berries, and since this period varies 

 more or less each season, it is impossible to give definite dates at 

 which the applications should be made. Hence the development of 

 the blossom clusters and the formation of the berries will doubtless 

 indicate more accurately the hatching period of the larva?. The 

 following spray schedule is based on the blossoming period of the 

 grape and the development of the berries: 



First application just previous to the blossoming period (see fig. 20) 

 to poison the larva? which feed in the blossom cluster, from about 

 June 8 to 14. 



The second application should be made immediately after blossom- 

 ing, at which time the larva? commence to feed upon the newly set 

 berries, and the application should be doubled over those portions 



