1909.] Insect, Fungus, and other Pests. 



75i 



Mass., very large cavities are formed, or the tuber may be 

 completely hollowed out. In such cavities hundreds of 

 millipedes are often present. Millipedes are often introduced 

 to the land in leaf mould or decaying vegetable matter. 

 Lime is the best corrective. 



Oospora Scab of Potatoes. — The scab produced by the 

 fungus called Oospora scabies, Thaxter, superficially 

 resembles that due to mechanical injury, but is distinguished 

 by the presence of the parasite, which appears on the 

 wounded portions as a delicate greyish bloom. The entire 

 surface of the tuber is frequently broken up, or scabbed; 

 in other examples the injured portions are more or less cir- 

 cular in outline, and scattered over the surface of the tuber. 



Beet, swedes, turnips, and carrots are susceptible to this 

 disease, and should not follow a crop of diseased potatoes, as 

 the fungus remains alive in the soil for some years. 



Nitrate of potash, at the rate of two hundredweight per 

 acre, has proved beneficial. 



Spongospora Scab of Potatoes. — This form of scab, due 

 to the Myxogaster called Spongospora scabies, Mass., was 

 described in detail in the Journal, November, 1908, p. 592. 

 The accompanying figure illustrates the type of wound pro- 

 duced by this organism, when potatoes are growing in fairly 

 damp soil. The certain proof that Spongospora is the cause 

 of injury is the presence of the very characteristic spores, 

 which form a snuff-coloured mass on the surface of the wound. 



Judging from the very large amount of material received 

 at Kew for examination, Spongospora scab is much more 

 prevalent in Scotland than in England. 



Cockroaches. — In connection with the note on cockroaches 

 which appeared in the April, 1908, issue of this Journal, 

 p. 45, it may be added that an excellent 

 Notes on Insect, method of combating these pests con- 

 Fungus and other sists in fumigating with bisulphide of 

 ^ ests,x carbon. If infested rooms can be left 



unused for a day or two, saucers con- 



* Notes on insect, fungus, and other pests, dealing with the specimens 

 submitted to the Board for identification, and their apparent prevalence, will 

 appear in this Journal month by month. The notes commenced with the issue 

 for June, 1907. 



