205 



in anticipating insect outbreaks. The work in connection with the 

 psrmanent establishment of the Coccinelhd, Novius cardinalis, has 

 been continued. The value of this insect in controlling the cottony 

 cushion scale [Icerya purchasi] has been demonstrated, and it is 

 thought that provision can be made to carry it through the winter. 

 The work of the station as a whole has developed along fundamental 

 lines, and enables the Division to foresee more accurately insect 

 disturbances from year to year and throughout the season. 



CoNR.\Di (A. F.). Report of the Entomology Tivjis\on.—33rd Ann. 



Rept. South Carolina Expt. Sta. 1919-20. Clemson College, S.C.. 



December 1920, pp. 41-43. 

 The work of the station has been continued chiefly along the lines 

 followed in previous years. Much work is being done in con- 

 nection with the cotton boll-weevil [Anthononms grandis] problem. 

 The period from oviposition to the emergence of adults averages 

 \1\ days ; eggs are laid about seven days after emergence, giving a 

 complete life-cycle of 25 days. 



Petherbridge (F. R.). Frit Fly {Oscinis frit) in Winter Wheat.— 



Ann. App. Biol.. Cambridge, vii, no. 4, February 1921, pp. 

 383-366. 

 The experiments here described prove that the larvae of Oscinella 

 {Oscinis) frit are capable of migrating to wheat from grass after the 

 latter is ploughed in. Bastard fallowing is advocated to prevent 

 attack by this pest on winter wheat, although after such a pro- 

 cedure there is always the danger of severe infestation by Hyleniyia 

 (Leptohylemyia) coardata (wheat-bulb fly). 



Howard (A.). The Influence of Soil Factors on Disease Resistance. 



— Ann. App. Biol., Cambridge, vii, no. 4, February 1921, pp. 



373-389, 5 figs. 

 There seems to be no doubt that the conditions of the active roots 

 profoundly affect the resistance of plants to the attack of pests. 

 Recent experiments confirming this theory are described. Examples are 

 given of the effect of soil aeration in connection with various diseases, 

 and with the insects, Psylla isitis, Buckt., on indigo, and Dysdercus 

 cingidatus, F., on Hibiscus cannabinus, in India. In all cases examined 

 root discolouration precedes and accompanies insect attack. The 

 connection between Aphids and winter irrigation has been observed 

 so frequently that more detailed investigations of the soil, root-system 

 and sap of the affected trees is urgently called for. Examination of the 

 root-system in the case of wheat attacked by termites in Bihar has 

 led to the discovery of the cause and a simple remedy that has since 

 been widely adopted on the indigo estates of this tract. The attack 

 by termites is apparently directly connected with the effect of soil 

 temperature on the plant. Many more examples of disease resistance 

 in other parts of the world must be examined before it is possible 

 to say how far immunity depends on morphological root fitness for 

 the environment and how far it is inherent in the natural resistance 

 of the protoplasm to the invasion of a pest. The object of this paper 

 is to suggest that in future more attention should be paid to general 

 facts of root development and the condition of the absorptive areas 

 of the root-system, both before and durmg the actual period of 

 establishment of disease. 



