14 



BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE. 



On small trees this equipment was used to good advantage to wash 

 the mature scale insects from their resting places. (Fig. 4.) All 

 limbs were within easy reach and the trees so small that a thorough 

 washing was possible. The results obtained were highly satisfac- 

 tory and the trees remained clean until reinf ested in the fall. 



On medium-sized trees the same apparatus was used, with the ad- 

 dition of a 12- foot platform and a 7 or 8 foot extension rod. This 



proved to be too te- 

 dious and was only 

 moderately success- 

 ful even when done 

 carefully. 



On large trees- it 

 was necessary to 

 have a greater pres- 

 sure and volume of 

 water in order to 

 obtain satisfactory 

 results. This was 

 obtained by using a 

 fire engine, supple- 

 mented with 1,000 

 feet of 24 -inch hose, 

 a short tapering noz- 

 zle with a circular 

 £-inch opening, and 

 a stand to facilitate 

 holding the nozzle. 

 (Fig. 5.) 



It was possible to 

 use a pressure of 

 160 pounds without 

 doing any damage 

 to the foliage al- 

 ready out. It proved 

 beneficial, in fact, by 

 removing all d e a d 

 twigs and branches 

 and incidentally giv- 

 ing the trees and 

 lawns a good irri- 

 gating. 



The crew consisted of one foreman, one engineer, and three hose- 

 men, this number being necessary in order to move the heavy hose 

 without delay. 



With this apparatus and crew 191 large trees were satisfactorily 

 washed in six days at an approximate cost of $1.20' per tree. Dur- 

 ing all the following summer the trees remained very clean, one or 

 two showing evidence of the presence of a few scale insects by a 

 slight drip. The writer estimated that about 85 per cent of the 

 scales had been removed. One year later, however, the trees were 

 again infested rather badly, owing partly to the remaining 15 per 

 cent and to a reinfestation from the surrounding well-infested trees. 



Fig. 4. 



-Washing young elm tree with garden hose and 

 nozzle to remove the European elm scale. 



