December, '21] moznette: avocado insects 467 



solution, one gallon to fifty gallons of water was applied. The weather 

 following application of the dusts was rather drj- although for several 

 days following ver^- heav>^ dews occurred which wet the foliage thorough- 

 ly, and a week later a heavy shower occurred in the grove. These heavy 

 dews and shower had very little effect on the sulphur dusted trees in 

 removing any of the dust. Where the lime sulphur solution was applied 

 it killed the red spiders by contact alm.ost immediately, and proved 

 satisfactory in controlling the red spiders over as long a period as did 

 the sulphur dust. 



Where a large acreage of avocados exists, and the red spider is the 

 only pest with which the grower has to contend, the dusting method 

 would make it possible for the grower to protect his orchard at critical 

 times from the attacks of the red spider. The dusting method is by far 

 the quicker method. 



There are other pests, however, with which the avocado grower has to 

 contend with such as the leaf thrips, Heliothrips hemorrhoidalis Bouche' 

 and the leaf hopper, Empoasca minuenda Ball. Neither the dry sulphur 

 dust or the liquid lim.e sulphur had any effect in ridding the trees of the 

 leaf thrips or the leaf hoppers. These two insects are usually present 

 and causing damage to the trees at the same time generally that the red 

 spider is carrying on its depredations, and which are not destroyed by 

 applications of sulphur in the dust or liquid form. To possibly control 

 these by the dusting method the writer procured a dusting material 

 consisting of the finely pulverized sulphur dust charged with nicotine 

 sulphate, 40% solution, in the form of Black Leaf-40. This material 

 was dusted in the same manner as was the dry dusting sulphur. This 

 combined material killed readily the adult and imjm.ature red spiders, 

 leaf thrips and a good majority of the leaf hoppers. The material, 

 however, did not adhere to the foliage for any length of time, even the 

 heavy dews removing the majority of the dust. This apparently was 

 due to the incorporation of the liquid nicotine sulphate to the dry 

 pulverized sulphur causing the sulphur particles to aggregate and forming 

 a wettable sulphur. In the case of the dr\^ dusting sulphur, it is due to 

 its fineness and dr}- condition when applied that it adheres so well to 

 the foliage. The continued heavy dews and subsequent shower removed 

 the majority of the combined dust from the foliage, and it was but a 

 short time after application that the red spiders were again present on 

 the trees in goodly numbers. This is readily explained as nothing effec- 

 tive remained on the foliage to destroy the young which later hatched 

 from the eggs not destroyed by the dust. Hence it is essential, that 



