98 Farmers’ Bulletin 1261. 
eral sprays were tried out in comparison with the foregoing dusts, 
viz—lime-sulphur concentrate, 1 part to 60 parts water, alone and in 
combination with 40 per cent nicotine sulphate, at the rate of 1 to 900 
in the diluted lime-sulphur solution. A portion of a block was 
reserved as a check. . 
Subsequent examination of the dusted and sprayed portions of the 
grove showed that the dusting method, where the dry dusting sul- 
phur in an exceedingly pulverized form was used, was equally as 
effective as spraying with lime-sulphur against the avocado red 
spider. The mites were not killed immediately on the dusted trees, 
but after 30 minutes were practically all dead. On examination 
of the foliage with a hand lens the sulphur was found very evenly 
applied, no portion of the upper surface of the foliage being free 
from the fine sulphur. The dry sulphur dust adhered remarkably 
well to the avocado foliage, which has a slightly pubescent surface. 
The dry sulphur dust remained on the foliage effectively over as 
long a period of time as did the liquid lime-sulphur against the red- 
spider mite. This showed that the foliage did not have to be wet 
with dew, but that the sulphur dust could be applied effectively to 
the dry foliage. 
Where a large acreage of avocados exists, and the red spider is 
the only pest with which the grower has to contend, dusting is 
much the quicker method of control. Where the lime-sulphur solu- 
tion was applied it killed the red spiders by contact almost imme- 
diately. 
Neither the dry sulphur dust nor the liquid lime-sulphur solution 
had any effect in ridding the foliage of the thrips present in consid- 
erable numbers on the trees. When the red spiders are present there 
are usually other pests, such as the leaf thrips and avocado lace-bug. 
To control these by the dusting method the writer procured a dust- ~ 
ing material consisting of the finely pulverized sulphur charged with 
40 per cent nicotine sulphate. This material was dusted in the same 
manner as was the dry dusting sulphur. This combination readily 
killed the adult and immature red spiders, the leaf thrips, and such 
lace-bugs as were present. The material, however, did not adhere to 
the foliage for any length of time, even heavy dews removing most of 
the dust. This apparently was due to the incorporation of the liquid 
nicotine sulphate into the dry, finely pulverized sulphur, which caused 
the sulphur particles to aggregate and also formed a wettable sul- 
phur. In the case of the dry sulphur dust the sulphur is in such a 
dry and impalpable state on the foliage that it adheres effectively. 
The continued heavy dews gradually removed most of the combina- 
tion contact insecticide from the foliage and in a short time after 
application the red spiders were again present on the trees in as 
