DISEASES AND PESTS 37 



upon by Bernard. The first symptoms are the appear- 

 ance of minute whitish spots ; these grow and become 

 grey-brown, with a narrow white border ; finally the 

 centre dries. The spots are usually elliptic in shape. 



The disease was first reported at Kempit in August 

 1905, and the Director of Agriculture recommended that 

 the infected parts of plants be burned, and that the 

 plants be sprayed with Bordeaux mixture. In January 

 1906 it was reported that the disease was making de- 

 structive progress, and Bernard was sent into the field. 

 It was found that in order to burn the diseased leaves 

 they had been cut and then carried across a field hitherto 

 free of infection to the place of burning. One field of 

 50 bouw, 5000 trees, and an adjacent one of 70 bouw, 

 7000 trees, had almost all the trees infected. The soil 

 was virgin and rich, and there was no dry season. There 

 were 150 bouw, 15,000 trees, a little over a year old, 

 3 kilometres away, separated from the diseased fields by 

 forest ; these were free from the disease. In the field of 

 50 bouw more than half of the trees were so seriously 

 attacked that there was already no hope of saving them. 

 About 1000 were already dead, and 650 had already been 

 replaced. In this field the trees were just over a year 

 old. In the 70 -bouw field the trees were recently set 

 out, and the disease was doing less injury. 



The period of incubation, as determined by putting 

 some diseased leaves in the crown of a sound isolated 

 tree, is about two months. The failure to get results 

 from the use of Bordeaux mixture in these fields is 

 attributed to the probable fact that the trees were 

 generally infected before it was used. The disease is 

 not regarded as dangerous except to weak trees. At 

 about the age of a year, they have used up the nourish- 

 ment in the parent nut, and are not at once in a 

 condition to vegetate without it vigorously enough to 

 resist the fungus. 



Bernard's recommendations are : 



1. That plants likely to be exposed be sprayed with 

 Bordeaux mixture — 2 kilograms of copper sulphate in 



