MISCELLANEOUS CROPS, 617 



( >n this account, selection of healthy plants becomes more a matter of 

 selecting healthy fields than of excluding diseased cuttings or stools. 



It lias been found unsafe to take plants from fields in which even traces 

 of either gumming or leaf seal. I can l>e discovered. Where not objectionable 

 for other reasons, the planting of clean plants of a resistant variety, such as 

 Malabar, on farms where gumming occurs, or any variety other than .Mahona 

 in the case of leaf-scald, is the safest course, for this also minimises the 

 risk of the disease spreading to the newly-planted clean Held from an 

 adjoining diseased block. 



In the ease of Fiji disease we have no highly resistant varieties from 

 which much aid may be expected. But selection of the cleanest fields, 

 followed by careful exclusion of an)' diseased stools in those fields, has proved 

 adequate for its control, without a change of variety. 



Yellow stripe disease, on the other hand, has a short incubation period of 

 two to three weeks, and is infectious at certain seasons only. Healthy plants 

 may therefore be selected from diseased fields without undue risk being 

 incurred, and change of variety on its account is not necessary. 



i'. Eradication of Disease in the Tounff Crops. — It is found in practice thai 



odd diseased cuttings sometimes creep in in spite of overy care being taken 

 in selection of plants. 



As most of these usually develop definite symptoms of disease during their 

 first three to four months growth, they can be detected and removed, and 

 their places filled with healthy plants at little expense, provided that only a 

 small number be present. 



This method of "cleaning up," to supplement selection of plants, is 

 especially useful with Fiji disease. 



When cultivation is completed and the cane laid by, further eradication 

 becomes laborious, and usually does not pay. If further diseased stools 

 appear, they may be dealt with when cultivating the young ratoons after the 

 plant crop has been cut for the mill. 



3. Dealing with Badly Diseased Crops. — Where the proportion of disease 

 is too high for the eradication of individual diseased stools, the whole crop 

 should be ploughed out as soon as possible, although it usually pays to 

 leave it until cut for the mill. Its further ratoonihg would usually be 

 undesirable, even though a payable crop might be expected, because the crop 

 would breed infection for dissemination to any healthy cane in the vicinity. 



4. Avoidance of Knife Infection. — It has been shown by careful trial, in 

 the case of both gumming and leaf-scald, that cuttings from healthy plants 

 may be infected by being cut with a cane knife previously used to cut 

 diseased cane. 



The risk may readily be avoided by disinfecting the cane knifes while in 

 use, by dipping them into disinfectant solution or into boiling water, on the 

 principle of the surgeon who sterilises his knives to prevent blood poisoning. 



Disinfection of knives is of most importance when stalks are being cut 

 into cuttings, but it should also be used whenever cutting cane which it is 

 intended to ratoon, on farms where even traces of these diseases are present. 



5. Attention to Drainage. — Defective drainage favours diseases generally. 

 This is especially the case with gumming, which may spread with great 

 rapidity and kill most of the cane on badly-drained areas, whereas it makes 

 little or no headway where drainage is really gcted. 



