296 Farmers’ Bulletin 1261. 
oil-emulsion sprays should be so timed as not to interfere with the 
lime-sulphur sprays. The oil-emulsion sprays should not be put on 
immediately following a lime-sulphur spray or foliage injury may 
be experienced. The two sprays will not mix. The oil emulsions 
have a cleansing quality and loosen sooty mold, lime, and any foreign 
matter adhering to the foliage. A great deal of benefit which would 
have been derived from the lime-sulphur will be lost by applying 
an oil emulsion over it. 
There are a number of ordinary commercial lime-sulphur concen- 
trates on the market which are satisfactory, or the grower can make 
his own lime-sulphur concentrate if he is prepared to do so. Since 
the lime-sulphur spray kills the mites largely by contact, it is im- 
portant that the spray be thoroughly applied in order to reach all of 
them. This is also true in the case of the thrips when the nicotine 
sulphate is incorporated with the lime-sulphur spray or is used with 
the fish-oil soap. From the writer’s observations, the lime-sulphur 
is not effective against the eggs of the red spider, as it kills only a 
small portion of them. The lime-sulphur is not dependent for its 
efficiency entirely on contact. Its effectiveness is more or less lasting, 
and consequently the young which may hatch from eggs not killed 
will succumb soon after. In about three weeks after spraying avo- 
cados for red spiders and thrips another spraying will usually be 
necessary to proteet the trees from further attack. Subsequent appli- 
cations will depend upon weather conditions and the activities of the 
pests during the winter season. Usually two sprayings, or three at 
the most, during the winter will suffice for both the red spiders and 
thrips. 
The writer in comparing the spray gun (fig. 20, 6) with spray: 
rods (fig. 20, a) has found that the spray gun gave better satis- 
faction, especially on large avocado trées. Where the rods were 
used, considerable inefficient spraying was done on the upper half 
of the tree. This was seen to occur especially during the latter 
part of the day, when the spray rod became heavy to the operator. 
In spraying the young grove, however, the rods work to a somewhat 
better advantage. 
DUSTING VERSUS SPRAYING FOR THE CONTROL OF THE AVOCADO RED 
SPIDER AND LEAF THRIPS. 
Certain contact insecticides which are being used in the liquid 
form for combating insects are also being manufactured in the dry 
powdered form as contact insecticides. These are being manufac- 
tured separately, and in combinations to be applied for a number of 
evils existing at the same time. Recently a number of orchard tests 
have been made by the writer to ascertain the relative merits of 
several contact insecticides in the dust or powdered form, alone and 
