==Wart Disease (Black Scab) of Potatoes== (=Synchytrium endobioticum=, Percival).—­This extremely infectious and destructive disease of the Potato has been given a variety of names in different parts of the country, but it is now generally known as the Wart or Cauliflower Disease, the latter term being attributable to the Cauliflower-like appearance of the outgrowth of the fungus.  This outgrowth first shows in the eyes of the young Potato in the form of small wrinkled warts.  These multiply and combine, thus creating a dark spongy scab which eventually decomposes.  Where the disease is very rife it attacks haulm as well as tubers, and a yellowish-green mass may sometimes be found just above or just below the surface of the soil.  As a rule, however, no outward indication of its existence is to be seen in the crop during the early stages of growth, but towards the end of the season the haulm of badly diseased plants often retains a fresh green appearance when the foliage of others, which are healthy or only slightly attacked, is dying off.

Infection is perhaps most commonly spread by the planting of diseased tubers.  Another frequent means of dissemination is caused by consigning infected haulm to the waste heap instead of to the fire.  The spores may also be introduced in manure from animals fed on diseased Potatoes in a raw state, and they may even be carried from one plot to another on garden implements or the boots of those who walk across infected ground.  Immediately any sign of the disease is observed it should be dealt with promptly and in no uncertain manner.  Every particle of the infected material must be carefully collected and burned.  Dig out the soil around all diseased plants and burn this also.  On infected land it is important that some crop other than Potatoes be taken in the season following the outbreak, and, if possible, such land should not be used for Potatoes for at least five or six years.  But where garden space is limited, a contaminated plot may have to be requisitioned for Potatoes within two or three years.  In such cases it is an excellent plan to dust the sets freely with sulphur at the time of planting and to repeat the application before earthing up.

Although for some years the unremitting labour of experts has been devoted to the investigation of Wart Disease, and innumerable experiments have been undertaken, no effectual remedy has yet been discovered.  It has been found, however, that certain Potatoes are resistant to the disease, and by order of the Ministry of Agriculture and Fisheries none but ‘immune’ varieties may be planted in districts scheduled as infected areas.  A notification of the existence of Wart Disease must be made to the Ministry immediately it is observed.