SOME ASPECTS OF SPRAYING AGAINST PESTS. 
223 
satisfactory mixture was found, which has since given good results. 
Summarizing the experience obtained, one may say that for ordinary 
lime wash the following conditions apply : 
(1) The lime should be good white lump lime of 98 per cent, 
purity. 
(2) It should be freshly burnt and not air slaked. 
(3) It should not be overburnt. 
(4) Twenty pounds should be used to ten gallons of water. 
(5) The best results are obtained by allowing it to slake for at 
least six hours, if possible until it is quite cold. 
(6) It should be strained through a sieve with sixteen meshes 
to the inch, and applied by means of a machine and nozzle especially 
adapted for lime spraying. 
(7) It must have time to dry on the tree before rain falls. 
With regard to lime mixtures the most noticeable thing is that 
the addition of nearly every substance injures the resulting coat. 
An improvement was found, however, in the following formula, which 
was the most satisfactory mixture obtained : 
Lime 25 to 30 lb. (depending on its freshness). 
Hide glue 2 lb. 
Potassium dichromate f oz. 
Water 10 gallons. 
It is essential for the success of this mixture that the lime should 
be thoroughly slaked and cold, since hot or partly slaked lime renders 
glue immediately insoluble. The crux of the mixture was the 
potassium dichromate. This salt, under the influence of light, has 
the property of rendering gelatine, the essential body in glue, in- 
soluble. It should be weighed out fairly accurately, as a moderate 
excess renders the glue insoluble before the spray is applied and a slight 
excess causes a very hard but too brittle coat. Recent experience has 
shown that this mixture is not very successful if applied during very 
dull weather. This is explained by the action of the dichromate. 
In sunny weather the glue is in a soluble state until it is sprayed on 
to the tree, when, under the influence of light, it becomes insoluble as 
the spray dries. If the weather is dull this does not happen. It is 
possible that by increasing the amount of potassium dichromate 
a better result might be obtained, but this has not yet been 
tested. 
The other factor which influences success in lime spraying is the 
time of application. When first this treatment was advocated the 
time to spray was said to be as late as possible, just before the buds 
started, but recent experience from growers and experimenters alike 
has shown that it may with advantage be done very much later than 
this. How late has not yet been exactly determined, but experiments 
are now in progress at Long Ashton to throw some light on this point. 
Trees are being sprayed with various cover washes at various stages, 
and the results are being noted. As it is difficult to describe in words 
