Common Potato Pests. 



173 



successful Wlietlier trap-crops are of any value under South African 

 conditions is not known. 



Literature . — " Root-knot, Gallworms, and Eelwornis," by C. 

 Fuller, Agricultural Journal of tlie Union of South Africa, Septem- 

 ber and November, 1913; "Root Gallwonn,'' by R. Jack, Bull. 147, 

 Salisbury, Rhodesia; "Economic Importance of Nematodes," by 

 •1. Sandg'iuund, South African Journal of Science, July, 192.1. 



The Potato Tfbek Moth (Phthorimaea operculella Zell.). 



Tlus insect is widely distributed and is considered to be the mosi 

 serious iusec1-]test with wbi(di the South Afj'ican potato-grower has to 

 contend. Tbf birvac : Iso attack toliacco .-iiid the stiid\b1aar (IhiluKi 

 strnnioniii )n) . 



Appearance of Infcslcd fofafocs. — 'J'he caierjtillars eal their \\a_\ 

 into the tubers and sometimes work right to the heart t)f the jx'lato, 

 while at other times they burrow just below the skin. The i)urr()ws, 

 especially the openings to them at the surface of the tuber, are usually 



The Potato Tuber Moth. 



Adult Moth above ; larva below at right ; pupa at left, wit h 

 sirle ■"lew of enlarged anal segment: all greatly enlarged. 



(After Ifotoiorl, f/'.iS. Dpptirtmenf of Aiiricnlturc.) 



marked by a quantity of coloured excrement. The eye i.s a ftivtuu ite 

 place for the entrance to a burrow. Sometimes the tubers are only 

 slightly injured, while at other times they may be entirely ruined. 



Life-history. — The adult is a small moth about two-fifths of an 

 inch long, and with a wing- expanse of about five -eighths of an inch. It 

 is greyish-brown in colour with obscure darker markings; the liind- 

 wings, which are whitish in colour and fringed with long hairs, are 

 hidden when the moth is at rest. The small shining white eggs are 

 laid singly either on the tubers or on the tops, and when the cater- 

 pillars hatch out they bore into the tuber, stem, or leaf, as the case 

 may be. In the leaf the larva commonly burrows between the upper 

 and lower surface, or it may fasten two leaves together and feed 

 between them. 



When full-grown the caterpillar is about half an inch long and of 

 11 diiiy-white colour with a greenish tinge. It now spins a light silken 

 cocoon, and within this it changes into a puptt. In storehouses the 



