502 Agncultural Gazette of .Y.^S'.TF. [July 2, 1920. 



Thrips Damaging Tobacco 



{AnapliQthri'ps striatus Osbourne). 



W. W. FROGGATT, F.L.S., Government Entomologist. 



The iiuportance of the study of insect pests infesting tobacco in Australia 

 has been emphasised by the damage sustained by the tobacco crop in the 

 Tamworth and Gunnedah districts this season. The appearance of countless 

 numbers of thrips upon the maturing leaves, causing them to dry, I'esulted in 

 a considerable reduction in the weight of the infested foliage. 



Thrips are minute insects with pointed^ cone-shaped mouths, with which 

 they cut the surface of the leaf and suck up the sap, causing the foliage to 

 become mottled and discoloured before it has matured. These insects, which 

 develop very rapidly, la}^ large numbers of microscopic semi-transparent eggs, 

 usually along the midrib of the leaf. The larval thrips, almost pure white, 

 but tinged with green or yellow, follow the veination of the leaf, where the 

 sap is most abundant, and as they increase in size and numbers finally scatter 

 all over the surfac<^. While feeding they exude a globule of watery matter 

 and this excrement forms a deposit of dirty specs all over the surface of the 

 infested leaves. These specs, in the case of tobacco, also damage the quality 

 of the dried leaf. 



It is rather femarkable that, though tobacco grown in the United State* 

 and Culm is subject to the attacks of many injurious insects, the writer can 

 tind no record of thrips among them. It is true that one species common iti 

 the United States is known under the scientific name of Thrips tabaci, but it 

 received this specific name from Professor Lindeman, who, when describing 

 it, recorded this thrips as a serious tobacco pest in Bessarabia. 



The thrips now found upon tobacco may have been in the Tam worth and 

 Gunnedah districts for some years, and even upon the tobacco plants in 

 saiall numbers ; yet it is evident that climatic conditions ha^'e caused them 

 to feui'n their attention to these plants, which, grown under irrigation, are the 

 only green crops in the district. All the grass and herbage upon which they 

 might have previously existed have been dried or eaten off under the drought 

 conditions that have prevailed during the last two years. 



Among the cosmopolitan species of thrips that have been identified and 

 recorded from Australia are two somewhat similar xpecies, that, to the casual 

 observer, might have been determined as our tobacco thrips. The first is 

 Thripn tabaci, Linden, which the writer has identified on onions ia the 

 Botanic Gardena, Sydney, at Gosford, and in several other localities. ITiis 

 is the species that did so much damage to roses in the suburban garden!* 

 of Sydney aomo years ago ; it was then popularly known as the " rose 

 thrips." It is somewhat remarkable that the opening buds of tlie light- 

 ooloured (yellow and white) roses suffered much more than th< se of the dark 



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