12 BULLETIX 1035, U. S. DEPAETIMEXT OF AGEICrLTUKE. 



which he has to contend, making it necessary to use liquid insecticides 

 in combination with a sulphur spray in some form for their control. 

 Up to this time the writer has not found it practical to use a combina- 

 tion of sulphur dust and 40 per cent nicotine,, sjulphate against the 

 insects of the avocado. ' "^^^^^^TifflS^j,,, 



LIME-SULPHUR CONCENTRATE. 



In using lime-sulphur concentrate spray on the avocado a number 

 of strengths were tried, e. g., 1 gallon of concentrate to 40 gallons 

 of water. 1 to 60, and 1 to 75. In spraying with lime-sulphur solu- 

 tion it was found through actual count that nothing is to be gained in 

 applying too strong a solution of lime-sulphur to red spiders on the 

 avocado. A strength of 1 gallon of the concentrate to 60 gallons of 

 water proved to be the most efficient, generally killing 99 per cent 

 •of the spiders and producing sufficient body as a spray on the foliage 

 to remain effective during the dry season against later hatching 

 young. Under certain conditions applications of 1 to 40 and 1 to 60 

 were too strong, and considerable damage resulted to the foliage from 

 burning, especially on the south side of the trees. When the tem- 

 perature is above normal during the winter season, or when the trees 

 do not attain a thoroughh' dormant condition, a strength of 1 gallon 

 of the concentrate to 75 gallons of water was found satisfactory. It 

 was also ascertained that it is not necessary to incur the extra expense 

 of adding a spreader of lime-sulphur spray, such as flour paste, glue, 

 or fish-oil soap, because good results were obtained without it. 



COMMERCIAL SODIUM SULPHID. 



Commercial sodium sulphid was used at a strength of 2 pounds to 

 50 gallons of water. It was ascertained that this spray killed approxi- 

 mately 95 per cent of the red spiders present. Because of its chemical 

 composition, however, the spray did not dry thoroughh' on the foli- 

 age. The hydroscopic condition so formed permitted the spray cover- 

 ing the eggs and foliage to be readily washed off b}' succeeding rains, 

 and nothing remained to destroy the hatching young. 



NICOTINE SULPHATE CONTAINING 40 PER CENT NICOTINE. 



At times the red spiders make their appearance during the fall 

 before the fruit is picked. At this time it is not advisable to use 

 any of the sulphur sprat's, as they adhere to and discolor the fruit. 

 By using 40 per cent nicotine sulphate at the rate of 1 part to 900 

 parts of water, with the addition of 2 or 3 pounds of fish-oil soap to 

 each 100 gallons of the diluted spray as a spreader, satisfactory re- 

 sults were secured. The spray, however, proved to be effective only 



