ENTOMOLOGY 289 



The tobacco capsid bug {Engytatus volucer Kirk.) punctures the 

 leaves, and causes them to contract and crinkle (Roberts 1930). It 

 is not a vector of the mosaic disease of tobacco, which has recently 

 been proved to be B. rhodesiensis Corb. A measure recommended 

 against it in Rhodesia is to plant in December so that the 

 plants will be well established before the peak of infestation in 

 April. 



The most serious pest of tobacco in Southern Rhodesia and 

 Nyasaland is probably the root-knot nematode {Heterodera 

 marioni Goodey), which, although not an insect, falls within the 

 province of the entomologist. A special investigation of this pest 

 has recently been undertaken by the Tobacco Research Board. 

 Other insects which attack tobacco in Rhodesia include cutworms 

 (chiefly Eiixoa segetum SchiefF), Tenebrionid beetles, both as adults 

 and larvae, a large cricket {Brachytrypes membranaceus Dr.), the 

 stem borer {Phthorimeaa heliopa Lw.), and the splitworm {Phthori- 

 meaa operculella ZelL). Tenebrionid beetles can be poisoned in the 

 adult stage, and a bait consisting of barium fluosilicate and maize 

 meal has given good results against the large cricket. 



A virus disease of tobacco causing stunted growth and malforma- 

 tion of the leaves has been experimentally transmitted in South 

 Africa by a thrips of the genus Frankliniella, which is close to F. 

 insularis Frank!., the vector of wilt-disease of tomato in Australia 

 (Moore 1933). The larvae were shown to contract infection from 

 diseased tomato leaves, and the thrips infected several species of 

 solanaceous plants, which may therefore serve as reservoirs for the 

 virus. 



Where infestation by insects causes a regular and known loss 

 without provoking danger of the kind caused by virus diseases, it 

 is enough to discover simple control measures that can be applied 

 readily by native labour. For this purpose experiments are made 

 to find suitable local adaptations of measures which are themselves 

 not new in principle. In connection with the cosmopolitan pests 

 of Citrus, for example, there is a continual search for satisfactory 

 sprays, bait, and mechanical means of control. In Algeria there 

 has been some work done on various oil sprays against Coccids on 

 Citrus (Balachowsky 1933), and in the Union of South Africa, Dr. 

 L. B. Ripley's new sodium fluosilicate bait for fruitfly has been 



