Eemedial measures are not practicable in the general way, 

 but it is said that if the plant is severed below the swelling, and 

 all but the strongest suckers removed, a fair amount of leaf will 

 be produced, provided the plant is young enough. 



THE TOBACCO MINER OR SPLITWORM (Phthorimcza opercu- 

 lella). This insect is closely related to the preceding, and it is 

 a very difficult matter to distinguish between the larvae of the 

 two insects. The tobacco miner, however, chiefly attacks the 

 leaves, and, although also found in the stems, is not known to 

 produce any swellings. The insect is also a bad pest of pota- 

 toes, not only mining the leaves and stems of the plants, but 

 boring the tubers. It thus possesses an alias in the form of the 

 potato tuber moth." 



The female moth lays her eggs singly on the plant. The 

 eggs hatch in from six to ten days, and the young larvae eat into 

 the tissues. They eat out the substance of the leaves in irre- 

 gular patches, leaving only the upper and lower skins. These 

 patches are semi-transparent when the leaf is held up to the 

 light, and the larvae may commonly be seen inside the leaf. 

 They have a habit of leaving old mines and starting new ones, 

 and this habit is of some importance in connection with control 

 measures. When full-fed the larva changes to a pupa inside 

 the plant, the moth under favourable conditions emerging in 

 about five weeks from the hatching of the egg. The time, 

 however, depends upon the temperature. 



As tobacco is not at present grown for the purpose of mak- 

 ing cigar wrappers in Southern Ehodesia, the injury to the 

 leaves is not of the same importance as it is in some other 

 tobacco-growing countries. The lower leaves of the plant are 

 chiefly attacked, and where priming is carried out, many of the 

 infested leaves are removed. Much good leaf is, however, 

 liable to attack, and it is no uncommon sight in the barn to 

 see hundreds of these caterpillars hanging by threads from the 

 drying leaves, or crawling rapidly over the ground in endeavours 

 to escape the uncomfortable heat. 



Preventive measures lie in covering the seed beds thor- 

 oughly at night, and in destroying the plants which might serve 

 as breeding places for the moth during the winter. This insect 

 also breeds in fhe common weed known as the thornapple or 

 ;< stinkblaar " (Datura stramonium), and this should be des- 

 troyed as much as possible about tobacco lands. 



