ROOT CROPS. 529 



Borne varieties recently imported give greal promise, and as they become- 

 better known will, no doubt, displace some of the varieties al present under 

 cultivation. The best of these recent introductions appear to be: — 



Yellow Strassbwrg. — A good yielding variety, producing long, yellow- 

 oured roots. The vine growth is abundant, with large leaves; a 

 mid-season variety, of high cooking quality. 

 Porto Rico. A vigorous and very productive variety. The leaves are 

 large, of the ivy-shape type; roots gulden in colour and 3pherical in 

 shape, large and inclined to crack ; mid-season in maturity. A good 

 table variety and a good keeper. 

 Triumph. — A high-yielding sort, of vigorous growth. The leaves are 

 of medium Bize and ivy-shaped; the roots an- of good shape, while 

 in colour, and of fair keeping quality. 

 Southern Queen. A fairly productive variety, bearing abundant growth 

 and large leaves. The roots are of good shape and size, of a cream 

 colour, and mid-season in maturity ; a fair table variety and a good 

 keeper. 



Diseases and Pests. 



Ear this crop has not shown itself susceptible to many diseases or pests. 

 It is possible this is due as much to the hardy varieties grown as to the 

 inherent ability of the plant to resist disease. In most districts where the 

 crop is grown, an occasional root may be found to be affected with rot in a 

 season, but not more. 



An exception must be made of the Richmond River district, however, 

 where a disease locally known as Curly Top caused serious loss on a 

 number of farms a few years ago. Experiments have been conducted by 

 the Department, but the real nature of the disease, and the actual method 

 of attack, remain somewhat obscure. The disease shows itself in the early 

 stages of the growth of the plant, generally in isolated plants throughout 

 the crop. In affected plants the leaves turn black and the wdiole plant wilts. 



In districts where the disease occurs, it is found that by planting in the 

 warmer months the vines grow more vigorously and are less susceptible to-' 

 the disease. The sweet potato is a tropical plant, and the ground is 

 apparently not warm enough in early spring to produce a sufficiently rapid 

 and vigorous growth. 



It is advisable to plant varieties which arc not liable to this condition. 



Convolvulus Hawk Moth. 



A hawk moth which is sometimes a pest of sweet potato is Protoparce 

 convolvuli, the caterpillar of which feeds on the leaves. The caterpillars 

 also attack convolvulus and privet foliage. These caterpillars are of a 

 general green colour, with paler-coloured diagonal streaks along the sides 

 of the body, and possess a spine or horn on top, near the hind end of the 

 body. The caterpillars may vary much in colour; some are yellowish, and 

 others, especially well-grown specimens, may be brown and almost black. 

 They feed voraciously, riddling and even eating the leaves completely off. 

 The caterpillars may grow to 3 inches in length, and are thick-bodied 

 When full grown, they bury themselves several inches down in the soil, 

 where they pupate, changing into a dark chocolate-brown pupa, with a 

 curved exposed beak, shaped like a .iug handle. The first brood of pupa? 

 produces a second brood of mo hs, which again lay eacs on foliage, and give 



