Enemies.
The sugar-cane crop is subject to the depreda tions of animals, insects and fungous parasites. Of the animal pests the rat is the most important. It is combated by the usual means, and, besides, is fought by fire and the mongoose. When burning off trash it is possible to entrap the rats of infested fields in a circle of fire. This is sometimes done most successfully. Opinion is divided as to the mongoose. The drawback to its introduction is the fact that it attacks poultry and native birds and useful small animals. By some these depreda tions are reckoned more than to offset any good it may do in destroying rats. There is no way of exterminating the mongoose, once it is introduced.
Insects.—The list of insect enemies of the cane is a rather formidable one. The worst are the bor ers, for the most part the larvm of beetles. These are fought by hand-picking and by agricultural methods, such as the rotation of crops, or the rest ing of the land, or the use of fire in destroying the "rotten" cane-stalks, which at considerable expense are sometimes gathered together and burned in heaps. Borers are sometimes hand-picked at a cost of hundreds of dollars per annum. Occasionally trap-crops are used, i. e., crops are planted at times calculated to attract the borers and are then cut green and destroyed by fire. In some regions one of the principal items of expenditure in connection with harvesting is that connected with the control of borers.
More than twenty beetles, several ants, several flies, about thirty butterflies and moths, numerous bugs, hoppers, aphides and scales, and several grasshoppers and crickets attack cane. Mites of various kinds are troublesome.
In fighting the insect pests various methods are employed. Where hand methods are applicable they are used. The use of insecticides is for the most part out of the question, the crop being so extensive and bulky, and impenetrable. The intro duction of insect and other parasites has been attended with marked success in some instances, and work in this line continues to promise well.
Stripping is closely related to certain insect pests, as it favors some and hinders others. This is one of the reasons for the great diversity of opinion and practice in connection with stripping.
The leaf-hoppers are being fought successfully in Hawaii by the introduction of insect parasites and predaceous insects.
The underground parts of the cane plant are attacked by a great variety of free-living and parasitic nematodes, and it has been recently shown that their attacks are a potent factor in various root diseases. The attacks of the parasites cause galls. These worms can be combated only by agricultural methods, one of the chief of which is a method of culture that exposes the soil as much as possible to the action of air and sunlight.
Diseases.—Twenty-five to thirty fungous pests of the cane are known, some of these being the most wide-spread and destructive of all the pests of the crop. Of these, two of the most serious, namely sereh and gumming, are not known to do serious damage in the United States or its possessions. Most of the others are probably as prevalent on American plantations as elsewhere, due regard being had to climate and other local conditions. The following is a list of the fungous diseases of cane somewhat in the order of their seriousness: Root diseases, rind disease, sereh, pineapple disease, red-rot, top-rot, smut, rust and various leaf and leaf-sheath diseases.
The nature of the cane crop precludes the use of fungicides except in connection with the rots that attack the cuttings after planting. Here fungicides come into play as explained on page 606. The remainder of the pests are fought by modifications of agricultural practices. Where the pests are abundant it is generally advisable to burn over the fields after each crop is removed. This results in the destruction of a vast amount of diseased material that would otherwise remain to infest the succeeding crop. Where the pests are not preva lent, the plowing in of such refuse is permissible. The destruction of infested cane of all kinds is sometimes accomplished by passing it through the mill at convenient times, as at the end of the week where the run is a weekly one. The crushing and heat kill everything thus treated and it seems prob able that this method will come into wider use. It is possible that in a large mill, it would pay to maintain a small set of rollers for this purpose.