root chops. 509 



The young eelworin larvae move throug i th( soil with considerable activity, 

 and "ii finding a root, bore their way into it. Once inside, the young worm 

 ceases its active movements, and begins to enlarge. J!> means pear- 



like organ within its mouth, it comment ed on the root tissues. Its 



presence irritates the tissues, and so stimulates them to enlarge, thus form- 

 ing ilic gall. The young worms are uol very resistanl to unfavourable 



weather conditions, and soil treal til aims at destroying the worms while 



still young and tender, as the eggs have a r< sistant coating, and the mat 

 females arc safely protected inside the root. Drying out of the soil, or 

 flooding the soil, is usually fatal to them in a comparatively short time. 

 S,.il kepi free from vegetation for about two years usually results in the 

 worms being killed out. 



There are a few plants that are practically immune to attack, so that the 

 most economic way of controlling Root Knot is by a proper system of rota- 

 tion, at least two years coming between each crop of potatoes. The following 

 plants are not at all, or very rarely, attacked by eelworm: — Barley, broom 

 millet, maize, Iron cowpea, peanut, pearl millet, rye, sorghum, velvet bean. 

 wheat, and winter oats. Potatoes used a- seed should be free from seal'. - 

 the scab areas may contain the worms. In a small garden, two or three 

 treatments of the soil, at intervals of about eight or ten days, with formalin 

 1 part in water 50 parts, applied at the rate of 2 gallons to a square yard, 

 uld be used. It is of advantage to cover the soil with sacking after each 

 application. 



Leaf Roll. 



The symptoms of this disease are somewhat varied, according t'i the - - 

 of infection reached. Two American scientists, Sehultz and Folsom, have 

 shown that the disease is spread slowly from plant to plant in the field by 

 aphids — possibly also by other sucking insects. Once a plant has I 

 infected, the contagion i> readily carried over from season to season in the 

 tubers, and practically all the tubers from an infected plant convey I 

 disease when \\><'i\ a- seed. 



In the first year of infection very little sign may ho seen on the leave: — 

 possibly a certain amount of curling of a few leaves. Tubers from plants 

 which have been infected give rise in the next year to plants showing 

 marked rolling of the lower leaves, and possibly of some of the upper 

 leave-. 



In addition, a proportion of the leaves display a form of yellowing, or 

 chlorosis. This is particularly marked along the rolled margins of I . 

 leaves. In varieties where pigment is present, the rolled margin may be 

 marked with purple. The manner of rolling is characteristic. The sides 

 of the leaves curl inwards from both sides, so as to form two rolled cylin- 

 der- parallel with the midrib. If a plant so affected i- examined, the s< 

 tuber may he occasionally found intact. In addition, the new tubers will he 

 found to he few in number and greatly reduced in size. 



In -"in,, cases the stolons, or -talks, which connect them to the plant, are 

 shortened. The disease interferes in some way with the manufacture and 

 transfer of the starch from the leaves to the tubers. I ! tul ers from affected 

 plants he again sown, there may he a proportion of marked failures, and 

 in any case a serious d< pression of yield- results. 



( 'mil ml. — A system of selection of hills must he practised. The best way 

 to secure g 1 potato -eed i- to raise it on the farm undi r one'- own obser- 

 vation. Farmer- who have large areas to plant should maintain a seed plot. 

 To commence this, they should -elect only tubers from hill- which are quite 

 free from Leaf Roll and which are not in proximity to affected plant-. 



