iTU JOUitA.UL Ol I'llE I)KrARlMKM Ol AciKlClLi CKK. Al'G.. 1922. 



COMMON POTATO PESTS. 



Compiled by R. liuiALKE, M.A., Lecturer in Zoolopy, Sohool of 

 Aoriciiltiire, rflon. 



It is necessary that an article* on potato culture should include some 

 information on the common insect pests with which the potato giower 

 has to contend, for these pests are one of the factors responsible for a 

 diminution in his returns. 



Detailed information on the pests that have been selected here 

 may be ob-tained from various departmental publications, and it is 

 for this reason that the present account is somewhat brief. For the 

 sake of convenience the sources froni which further informaticr may 

 be obtained are indicated in the " literature paraoraph,*' which iei- 

 ini nates the discussion of each pest. 



Root Gall-wou.m [Hetervdera radicicola (Greelf) Miiller.] 



Root oall-wonu disease of potatoes is common in the potato- 

 gTOwing" districts of the Union, and complaints are frequently 

 received. It is not caused by an insect but by a kind of plani-feedino- 

 worm so small that it can hardly be seen with the naked eye. Besides 

 tttackiufi' potatoes thi.s worm also causes enlargements of the roots of 

 peach, fig, grape, banana, pomegranate, tobacco, beel, beans, cowpen, 

 tomato, watermelon, cucumber, squash, pumpkin, carrot, i)arsnip, 

 carnation, sweetpea, snap-dragon, and many other i)lants. The list 

 of host plants is a very large one, and more than 500 species have 

 been recorded as being attacked l)y this parasite. 



Appearance of Diseased, Potatoes. — The surface of a diseased 

 potato is more or less wrinkled and' covered with nodules or small 

 lumps; in early stages of the infestation the potato may be firm and 

 the nodules so inconspicuous that they are easily overlooked, but when 

 the disease is more advanced the nodules are prominent, and the 

 potato is more or less shrivelled, and of a softer consistency than 

 normal. If a badly infested potato be cut open a number of small 

 brownish spots a little smaller than the head of a pin will be seen at 

 a distance of about quarter of an inch or less beloAv the surface. If one 

 of these brown spots be opened carefully and examined with a lens, it 

 will be found to contain a very small white pear-shaped object; this 

 is the gravid female worm, which has assumed the swollen appearance 

 because of the large number of eggs within her body. In early stages 

 the areas in which the worms are emliedded may l>e slightly or not 

 at all discoloured. 



Potatoes which are badly diseased may shrivel up 1o half the 

 natural size, are softer and less nutritious than normal, and not 

 desirable for human consumption. The presence of the worms in the 



* "Potato Culture," by G. J. Bosman. published in .Tuly. 1922, issue of the Jonrna 



