I 
INTRODUCTION 
7 
to an insufficient food supply, but it is also occasionally 
due to excessive exposure to beat and sunlight. The 
destruction or injury to the roots may be due to an 
underground fungus or to some insect such as the grub 
of a cockchafer biting through them ; again, it may 
be due to their having reached poor soil, or having 
exhausted most of the accessible nutriment. The 
yellowing of the leaves is also noticeable in plants 
growing in water-logged soil. 
When a plant is weak from insufficient food it is 
much more liable to attacks from insects and fungi, and 
where a plant has been injured by a pest, it is advisable 
to manure it, so as to give it a fresh start and enable it 
to resist the attacks of the pest. 
In the case of turmeric and ginger, the yellowing of 
the leaf is a preliminary stage in the death; of the leaf, 
and is one of the signs that the plant is passing into 
a resting stage. At this time the plant is ready for 
digging, and the yellowing is therefore a normal con- 
dition. 
INSECTICIDES 
Many different insecticides have been placed on the 
market by horticultural firms. In most of them the 
poisonous part consists of nicotine, or some form 
of arsenic. Nicotine solutions are prepared by soaking 
common or waste tobacco in water, enough being used 
to cover the tobacco. When the solution is of the 
colour of strong tea it is diluted and sprayed or watered 
over the plants. Usually, in the East at least, tobacco 
good enough for this purpose can be obtained cheaply. 
Arsenites of copper, Paris green and London purple 
are often used, but I think it is better to avoid them, 
as they are apt to burn the foliage, and there is a 
probable risk of poisoning from them. 
Kerosene emulsion is one of the best insecticides. 
It may be made with condensed or sour milk or with 
soap, the latter being more generally used. 
