92 Habits of the Tomato Moth 



cost an insignificant sum, occupied two hours to each house, and secured 

 effective control for half the growing season. 



This block was heated up in January and used for propagating. 

 Consequently it was planted late and it was possible to give it the 

 second spraying well on in May. When plants are put out in March to 

 give early fruit at the beginning of June the second spraying could not 

 be done after the end of April. As the blocks which receive these plants 

 are usually unheated till the beginning of March, the first moths are 

 later than in the case just considered. They will therefore be still 

 emerging in numbers when there is much new unprotected growth on 

 the plants, and the control will be less thorough than that described. 

 This explains why those growers who have used the arsenate have found 

 that, in spite of it, a few larvae are seen fully fed at the end of June. 

 The offspring of these, and possibly of a few moths that have entered 

 from outside, cause a heavy infestation in August and September, though 

 less heavy than where spraying is not practised. It is therefore necessary 

 to employ additional means of control. 



Experiments were made with tuba root (Denis), a quantity of which 

 was obtained by Mr Fryer, Entomologist to the Board of Agriculture. 

 The specimens tested were prepared by Mr Tattersfield of the Rothamsted 

 Experimental Station. In ordinary use this substance is said to be not 

 poisonous to man and it could be used on plants in any stage. It was 

 tested in several ways: (1) as a dry dust, alone and in dilution with 

 powdered earth; (2) with saponin in watery suspensions, at various 

 strengths from -25 per cent, to 10 per cent, by weight of the powdered 

 root, mixed and strained through muslin; (3) with saponin in watery sus- 

 pensions of an alcoholic extract (six times the strength of the powdered 

 root) at various strengths from -08 per cent, to 2 per cent, by weight. 



Tomato plants in pots were dusted or sprayed with these and infested 

 with larvae collected in the nurseries. The dusting was unsatisfactory 

 as it made the plants dirty and encouraged the growth of moulds. It 

 need not be discussed further. The watery suspensions of the powdered 

 root killed the larvae at a 10 per cent, strength, but a 5 per cent, strength 

 failed to do so within a reasonable time. These strong mixtures also dirtied 

 the foliage. Suspensions of the alcoholic extract proved very satisfactory 

 sprays on an experimental scale. A series of 18 experiments showed 

 that one part of this substance by weight in a thousand parts of water is 

 a sufficiently potent spray. A plant sprayed with this was infested with 

 12 half -grown larvae which were confined to one leaf by means of a 

 sleeve. Two days later seven of these were dead, and eight days after 



