Sept. 1906. J 



249 



Plant Sanitation. 



insects. It can be ploughed into the soil, mixed with the earth in holes prepared 

 for planting, or dibbled into the soil around growing plants. It is said to slowly 

 give off a noxious gas which kills the insects without injuring the plants. That it 

 will kill subterranean insects, I have proved to my satisfaction, but my experiments 

 are too recent to show its effect upon the plants. 



We have— in the Cockchafer grub— a very troublesome pest of young rubber 

 plants. I have a report of over 3,000 plants being killed by this pest in a single small 

 clearing. I procured a number of healthy living specimens of the grubs for the 

 purpose of experiment. A few of these grubs were introduced into a series of pots 

 containing growing Hevea plants. The soil in half the number was treated with 

 4 Vaporite ' (1 oz. to each pot), the remainder being left untrea ted as a control. 

 Within a few hours the grubs in the treated pots had come to the surface, showing 

 signs of distress. Twenty-four hours later, these grubs were all dead, while those 

 in the untreated pots remained below the soil — presumably in good condition. A 

 number of the grubs were placed in each of two biscuit tins filled with loose soil. 

 An ounce of ' Vaporite ' was mixed with the soil in one of the tins while the other 

 was untreated. Examination after forty-eight hours showed the grubs in the 

 one tin to be quite dead, those in the other tin remaining healthy and active. This 

 mixture therefore would seem to be of real value against cockchafer grub and other 

 subterranean insects. It should be particularly useful for preventing the attacks 

 of cut-worms in vegetable gardens, and might be tried in cases of gall-worm« 

 (Nematodes) on the roots of plants. Its employment is suggested against wire- 

 worms, millepedes, and against the bulb-borer of the cardamom plant. 



