INJURIOUS INSECTS OF 1904. 87 



spraying compound (except Kero-water), which it was desired to apply 

 to nursery trees. Our tank, resting on a platform between the wheels, 

 readily seen in the photographs, was made out of strong galvanized 

 iron and was two feet ten inches in diameter and three and one-half 

 feet high, holding about 165 gallons ; a faucet at bottom behind 

 allowed the emptying of the tank at any time. A fourteen-inch square 

 hole on top with cover afforded opening for filling. 



A heavy and steady horse was used with the cart, and an old saddle 

 on the back of the animal seemed to relieve his back of any undue 

 strain. However, as stated above, the weight was so well balanced on 

 the axle that the outfit was not at all severe on the horse, and was 

 drawn when the tank was from one-half to two-thirds full with appar- 

 ent ease. 



WORK IN THE FIELD. 



The tree hopper was first observed this season in various nurseries 

 early in July ; on July 4th in one in Southern Minnesota, where it 

 rapidly grew very abundant. On July 8th it was found to be doing 

 destructive work in another large nursery in Southern Minnesota, 

 and was abundant on the Station grounds from about July 15th. It 

 was also found to be very bad in nurseries in Southeastern Minnesota 

 and extremely abundant in Wright county nurseries on July 21st. 



One of the large nurseries referred to above was chosen as the 

 field of our experimental work. We had planned to spray early in 

 July, but owing to delay in getting the cart completed, the first 

 spraying was not given until July 14th, at least ten days later than 

 intended. At that time kerosene emulsion was used at the rate of one 

 part of stock emulsion to twelve parts of water. The machine worked 

 perfectly, one man and one pump being sufficient to envelope each tree 

 in the row in a complete fog. In this fog were thousands of hoppers 

 iiying from the trees, but unable to escape the spray. 



This strength of emulsion, however, while it killed the young 

 hoppers, did not permanently affect the adults. We therefore, on 

 July 19th, increased the strength, using one part emulsion to ten of 

 water. This in no way injured the trees, nor did it, unfortunately, 

 kill the adults, which were very numerous at that date. 



Learning from the Missouri Station that they were using a 

 mechanical mixture of kerosene and water (10 per cent), with con- 

 siderable success, I sent for a Kero-water pump, known as the "Peer- 

 less," which is seen in one of the photographs (Fig. 84) fitted to the 



