62 



milling should be destroyed, preferably by burning, in order 

 to prevent the emergence of any immature insects which 

 may be present in them. The practice of destroying all 

 rotten and insect-affected canes has an important "bearing 

 in connexion with otherpests and diseases of sugar-cane. 



Natural Enemies. The moth borer is attacked by small 

 parasitic insects which destroy the eggs. One of these 

 (Trichogramma pretiosa) is shown, much enlarged, in Fig. 64. 

 The female parent of the parasite inserts its eggs into the 

 eggs of the moth borer. When the eggs of the parasite 

 hatch they produce minute grubs which destroy the develop- 

 ing moth borer in each egg attacked in this way. Moth 



X3& 



Fig-. 64. Parasite of the eggs of the moth borer 

 Much enlarged, {Imperial Dept. Agric.) 



borer eggs which contain the parasite can be distinguished 

 from those which are not parasitized by their darker colour. 

 When eggs are being collected, those parasitized should, if 

 possible, be left in the field, but as it is difficult to carry 

 out this practice satisfactorily, it would be better to 

 have all collected eggs brought to the edge of the field, 

 to the mill yard or a similar place, and put into large trays. 

 The parasites on emerging would be able, in their winged 

 condition, to fly back into the field in search of fresh eggs 

 to attack. The newly hatched caterpillars could be pre- 

 vented from leaving the tray by means of a small trough 

 containing water, fastened around the top edge of the tray, 

 or by a band of some sticky substance such as molasses, tar 

 or tanglefoot, which would prevent the larvae from crawling 

 out. After three or four days the collected leaves should 

 be thrown into cattle-pens, where any caterpillars would be 

 destroyed either by being eaten or by being trampled with 

 ^he manure. 



