384 STATE HORTICULTURAL SOCIETY 



as it not only makes the mixture spread and adhere to the leaf better, 

 but prevents burning the foliage. 



SPRAYING CUT-LEAVED BIRCH. 



These trees constituted a small block in one of the Geneva nurseries. 

 Nearly all of the trees were badly infested with thrips [Thrips sp.]. 

 These are very small, almost microscopic insects, which feed on the 

 soft -parts of the leaves, soon causing them to wither and die. They are 

 frequently very injurious, and are well known to both gardeners and 

 fruit growers. They are hard to reach with insecticides, as they fly 

 away as soon as disturbed by the spray mixture. The trees in question 

 were beginning to show the injury which the insects were causing before 

 the spraying was done. In all cases much pains was taken to wet both 

 upper and under surfaces of the leaves. 



Experiments. — About the middle of June the block was sprayed with 

 a solution of whale oil soap, 1 pound to 7 gallons of water. After wait- 

 ing tAvo days no beneficial results were apparent. The block was again 

 sprayed with whale oil soap, 1 pound to 4 gallons of water. This had 

 the effect of keeping the insects away for a few days, but injured the 

 foliage slightly during one or two warm bright days which followed 

 the application of the soap. In about six days from this last apj)lication 

 the trees were again sprayed, this time with whale oil soap, 1 pound to 

 7 gallons of water, with the addition of flowers of sulphur, 1 oz. to each 

 gallon of solution. This proved much more effectual than either of the 

 other applications. Another application of the soap solution with the 

 sulphur added was made a week later. Although this species of thrips 

 continued abundant throughout the season on other ornamentals in the 

 immediate vicinity of the block of birch, no further injury of a serious 

 nature resulted to the sprayed trees. 



Conclusions. — These experiments indicate that thrips can be held in 

 check by a whale oil soap solution, 1 pound to 7 gallons of water, with 

 the addition of 1 oz. of flowers of sulphur to each gallon of the solution, 

 when attacking trees similar to the cut leaved birch. It should be remem- 

 bered that it is important that the leaves should be drenched on both 

 upper and under surfaces. 



EXPERIMENTS IN FUMIGATING NURSERY STOCK. 



These experiments have only just begun and hence require but brief 

 mention here. Fumigating nursery stock is usually done for the purpose 

 of killing San Jos^ scale. If fumigation can be made practical in the 

 large cellars used by nurserymen, it will be an inexpensive way to treat 

 a large amount of stock, and a preventive to the spread, not only of San 

 Jose scale, but other insects, such as woolly aphis, bud moth, pistol-case- 

 bearer and other injurious species. p]xperiments along this line are being 

 conducted in the insectary at the station and in one of the large frost- 

 proof cellars of the Chase Nursery Co., at Rochester. The cellar is 80 

 ft. long, 40 ft. wide and 16 ft. high. This was filled with fruit trees of 

 all varieties and fumigated with hydrocyanic acid gas. Before the gas 

 was generated, twigs infested with the woolly aphis and the pistol-case- 

 bearer were placed in different parts of the cellar, including the remotest 

 parts and under some of the piles of trees. The trees were exposed all 

 night, 14 hours. The temperature in the cellar was a little above freez- 

 ing. The twigs were carefully examined and all of the lice were dead. 



