506 Agricultural Gazette of N.S.W. [July 2, 1920. 



In dealing with all plant-infestiug insects of this type, one must start from 

 the beginning and find out where their eggs arc deposited so that their 

 original breeding ground can be treated. The thrips in the tobacco fields 

 visited by the writer were depositing tiieir eggs on the undersurface of the 

 tobacco leaves, then nearly ready for cutting. Both the larvie, in all stages 

 of development, and the perfect winged thrips were feeding upon the leaves, 

 which showed a discoloured mottled tint, as shown in the illustration. From 

 their action a certain per centage of weight would be lost ; and the dirt and 

 exci'cnient dropped all over the surface of the leaves would not improve the 

 quality of the dried leaf. Fortunately the plants were so near maturity that 

 the owners set to work and cut the leaves. These might have gained a little 

 in weight if they had been left longer, but the owners wisely did not take 

 the risk. 



In some of the fields Avhen the main crop was cut 'down the butt of the 

 stem and the roots had been left in the rows; these threw out vigorous 

 shoots, and the growers were expecting a second crop. On examining these 

 shoots it was found that they were covered with winged thrips. As the 

 maturing tobacco plants were cut, the winged thrips, disturbed by the 

 operation, swarmed over every green thing left in the paddock, and among 

 them weie these second crop shoots. 



The destruction of all plants and waste material in the paddock, either by 

 ploughing in or burning, after the tobacco had been cut and removed, would 

 destroy all the wintering thi'ips and their eggs. Spra3nng with a .soda soap 

 wash in the earlier growth of the tobacco plants would kill any active tlirip.s 

 larvie. Some growers experimented with burning sulphur to the windward 

 side of the tobacco plants, hoping thus to suffocate or drive the thrips out; 

 the only result was the scorching of some of the foliage. Sulphur dusted on 

 the underside of the leaves is very effective against thrips on orchard trees ; 

 but if sulphur remains on tobacco foliage near to the time of cutting it 

 might spoil the'diy leaf. 



Applied Entomology. 



In earlier days entomology was looked upon as a pastime for the spare 

 mofnents of those who cared to turn their attention to it, or as a business 

 confined to dusty museum^, without any practical application whatever; 

 the true significance of the study was not then apparent. . . . Gradually 

 the practioal side developed, and has since continued to develop, until at 

 the present time economic entomology is recognised by agriculturists as an 

 important adjunct to the study of the actual crop production, without some 

 knowledge of whish the cultivator of plants is likely to meet with obstacles 

 before his harvest i? over, or his products in the hands of the consumer. — 

 The Philippine Agricultural Review. 



