306 The Potato Crops 



leaves, which turn brown and the edges roll up and die. 

 Control: Keep the foliage protected by thorough spraying with 

 bordeaux mixture alone or in combination with arsenate of 

 lead, taking care to hit both surfaces of the leaves. 



Potato stalk-weevil (Trichoharis trinotata). — A bluish 

 gray snout beetle, 1/5 in. long, which lays its eggs on the stalks 

 of potato. The larva is a grub, yellowish white, legless, % in. 

 long when mature. Its presence is indicated by a wilting and 

 dying of the leaves. Control: Practice clean farming and 

 collect and burn the vines after harvesting the crop. Destroy 

 all solanaceous weeds. 



Common stalk-boreb (Papaipema nitela). — A caterpillar, 

 VA in. long when mature, that bores in the potato stalks in 

 gardens of small patches ; not usually found in large com- 

 mercial fields except along the edges. Until the last moult 

 it is grayish brown with a white dorsal stripe and two white 

 stripes on each side, the later stripes being broadly inter- 

 rupted toward the front. The parent moths lay their eggs 

 in the fall on the stems of such weeds as ragweed, pigweed 

 and dock. The eggs hatch the following spring and the larvse 

 at first attack weeds, migrating later to potato. Control: 

 Clean cultivation and the destruction of weeds around the 

 potato patch. 



Potato tubeb moth (Phthorimwa operculella) . — A serious 

 potato pest in Texas and California. The parent insect is a 

 yellowish brown more or less spotted moth. The eggs are 

 deposited in the field early in the spring. On hatching the 

 larva enters the leaf, producing a blotched line and then 

 bores down the petiole into the stalk, causing the branch 

 to wilt. Reproduction is continuous throughout the season. 

 Some of the caterpillars migrate from the stalks to the tubers 

 and where the soil is loose the' moths may lay eggs on the 

 tubers. At digging time, if the tubers are left exposed in the 

 field during the afternoon or night, the moths will lay eggs 

 on them. The larvse burrow through the potatoes in all direc- 

 tions, causing decay. In storage the insects continue to breed 

 as long as the potatoes are in condition to serve as food. 



