226 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY, 
months instead of three or four weeks. That is the first advantage. 
The second is that in winter labour is abundant, while in spring, and 
still more in summer, ordinary cultural operations are quite enough, 
to employ all the labour available. A third advantage is the thorough- 
ness with which it is possible to cover a tree in the dormant stage. 
There are no leaves to take the fluid, so that less may be used, nor 
do they afford the twigs protection from the fluid by lying close 
against them under the impact of the fluid, as so often happens in 
summer spraying. A fourth advantage is that, given an effective 
spray, no further spraying need be done during the summer. There 
are thus four distinct advantages, namely : 
(1) Choice of time for spraying. 
(2) Availability of suitable labour. 
(3) Thoroughness in application and absence of waste of material. 
(4) Freedom from further treatment. 
While these advantages are sufficiently obvious, it is not pretended 
that there are no difficulties. The chief is of course that of finding 
any substance that will really kill insect eggs. It is not indeed likely 
that, after Nature has been experimenting untold years in producing 
eggs that shall resist winter conditions, man should immediately 
find some means of destroying them. The insect egg-shell is of a very 
resistant nature, being composed of a substance called " chitin," which 
is allied to hair, horn, hoof, and similar bodies. Nearly all chemical 
reagents are without action on it. Only the strongest, like certain 
concentrated acids, attack it, and these naturally are not adapted for 
spraying purposes. 
The chief pests which exist in the egg stage on fruit trees include 
many kinds of aphis, apple-sucker, mussel scale, red spider ; certain 
moths, such as winter, lackey, and vapourer moths ; and last, but by 
no means least, capsid bugs. 
This is a formidable list, and includes some of the most serious 
fruit pests. The possible means of attack may be considered under 
three headings : 
(1) Mechanical. 
(2) Physical. 
(3) Chemical. 
Most of the eggs in the above list are laid simply on the bark, being 
usually fastened by a thin layer of cementing material. Apple-sucker 
and capsid bugs are exceptions to this. The former possesses a process 
which extends some way into the cortex and serves as an anchor • 
while capsids' eggs are often partly or wholly embedded in the cortex. 
With these two exceptions it would appear theoretically possible to 
apply a thick cementing coat which, when dry, would tear off the 
enclosed eggs. An ordinary lime wash is not strong enough to effect 
this, though it is possible that where such a coat flakes off, and is not 
washed off, some eggs are detached. All attempts to prepare a cover 
wash that' would have these desirable properties failed. 
