PRESIDENTIAL ADDRESS SECTION D. ( J 



insect parasitism is slow and tedious, and lience no time should 

 be lost in doing- the utmost possible to perfect our knowledge 

 along that line. 



Eesults Achieved. 



Thus i'ar attention has been paid t-o unsolved problems; 

 but lest someone get the impression that no results of practical 

 value have been achieved, I shall emphasise the fact that certain 

 problems have been brought to the point where control is 

 possible. The elucidation of the life cycle and economy of the 

 bont tick in its relation to the disease known as lieartwater in 

 sheep and g'oats and cattle has made it possible for the merino 

 sheep and the Angora goat to be brought back to the farms 

 which farmers left in despair 25 or 30 years ago. A detailed 

 knowledge of the ticks concerned in the transmission of East 

 Coast Fever in cattle has made it possible to prevent the disease 

 sweeping like a blight over the stock-raising areas. 



At one time the wine and grape industry was threatened 

 with extinction from the g-rape Phylloxera, but the discovery 

 of a resistant stock saved the situation. The Australian bug 

 threatened the life of the citrus industry and a wide range of 

 other plants as well, but the introduction of its natural enemy 

 {Novius cardinalis) turned failure into success. The peach 

 trees were smothered with white scale (Diaspis pentagona) 

 and the prune industry languished under the burden of the 

 Bryobia mite, till a critical study of the old California lime- 

 sulphur-salt wash showed the polysulphides to be the essential 

 ingredients. As a result, we now have an almost perfect insecti- 

 cide in commercial form, not only for the tree pests named, 

 but for sheep scab as well. The fruit fly was thought to be of 

 such importance that one farmer declared that if anyone found 

 a way to control it, he would write his name in gold all over 

 South Africa! A means of control was found in due course, 

 and the fruit-growers have received ample returns in golden 

 sovereigns; but the golden promise has been all but forgotten. 

 Through the use of arsenite of soda, locusts, which once held 

 sway, no longer hatch and feed and take wing at will in swarms 

 to darken the heavens like an emblem of Divine displeasure to 

 inspire the timid with fear. 



Let it not be imagined that because I used the expression 

 " results achieved " I consider that there is nothing more to 

 be done. Far from it I The true position is that we have 

 readied a stage where we can control certain pests to advantage. 

 Still more effir-ient means no doubt await discovery or applica- 

 tion to present conditions. As hinted in an earlier jiaragraph, 

 the sun is only rising. For 25 or 30 years we have been using 

 i:)russic acid (hydrocyanic acid gas) for the destruction of insect 

 jiests by fumigation, and the process seemed practically perfect. 

 Circumstances arose which indicated the possibility of improve- 

 ment, and a search through the literature revealed the fact that 

 at the beginning of last century it was demonstrated that the 

 gas could be reduced to liquid form by cooling. The applica- 

 tion of this to modern conditions has revolutionised fumigation 

 and placed it on a more nearly scientific basis. 



