74 



THE AGRICQLTURAL NEWS. 



March 2, 1912. 



INSECT NOTES. 



SUGAR-CANE INSECTS OF HAWAII. 



The sugarcane insects of Hawaii are dealt with in Bul- 

 letin 93 of the Ikireau of Entomology, United States Depart- 

 ment of Agriculture, by Mr. D. L. Van I line, who was for 

 several years Entomologist of the Hawaiian Agricultural 

 Experiment Station. The information given herewith is 

 abstracted from the bulletin mentioned, and should be of 

 interest to growers of sugar-cane in the West Indies. 



The Hawaiian Islands, which form a territory of the 

 United States, lie between latitude 18° 54' and 22° 15' North 

 Latitude, about 2,100 miles south-west from San Francisco. 

 The climate is similar to that of the islands of the Lesser 

 Antilles. 



The principal sugar-cane pests are four in number : the 

 sugar-cane leaf hopper (PerlcinsieUa mcchirkida. Kirk.), 

 the Hawaiian sugar- cane borer {Sjjhenophorus obscurus, Boisd.), 

 the sugar-cane leaf-roller {Omiodes accepta, Butl.), and the 

 sugar-cane mealy-bug (Pseudococms calceolaria e, Mask.). 



The sugar-cane leaf-hopper was introduced into the 

 Hawaiian Islands from Queensland before 1900. The species 

 occurs throughout the sugar-cane areas, both in Australia and 

 in Hawaii, and it has been recorded as occurring in Java. 

 This insect spread rapidly over the sugar-cane districts of 

 the Hawaiian Islands, and early in 1903 became generally 

 abundant throughout the cane fields of the Hawaiian 

 Territory. 



The eggs of the leaf-hopper are often deposited beneath the 

 epidermis of the sugar-cane stalk, in the internodes, and it is 

 probably because of this habit that the leaf hopper was intro- 

 duced into Hawaii, the eggs being concealed in cane cuttings 

 imported for planting. 



The adult leaf-hopper is attracted to light, and this 

 characteristic accounts for a considerable amount of spread 

 locally, steamships and railway trains as well as the bright 

 lights of the sugar-cane factories being responsible for dissemi- 

 nation of the insect to a large extent. 



During the severe outbreak of leaf-hoppers in Hawaii, 

 in 1903, the adult insects were often observed to migrate in 

 enormous swarms, flying with the prevailing wind. The 

 infected area was probably greatly increased by these 

 migrations. 



The eggs of the leaf-hopper are often deposited in slits in 

 the epidermis of the leaves and stalks of the sugar-cane. The 

 time required for them to hatch, in the laboratory, is fourteen 

 days, while the entire life-cycle occupies a period of about 

 forty-eight days. It is recorded also that in one trial with 

 infested cane cuttings, the eggs continued to hatch for 

 a period of thirty-eight days. This will serve to show the dan- 

 ger that exists of introducing the leaf-hopper in cane cuttings 

 imported into any country for planting, since the manner in 

 which the eggs are deposited in the cane, and the length of 

 the period over which the young continue to appear, would 

 make it possible for one shipment to infest an area far remote 

 from the place of export. 



The control of the leaf-hopper falls under several heads, 

 such as the burning of the trash, the selection of cane varieties, 

 cultural methods and diversification or rotation of crops. The 

 use of insecticides, stripping off the mature leaves, and the 

 collection of adult insects by means of nets, have all been 

 tried and abandoned. The cutting down and burning of 

 the canes over the centres of infestation resulted in the 

 destruction of the eggs and immature insects, but many 

 adults escaped to adjoining fields, by flight. 



The burning of the trash, after the cane is harvested, is 

 the most effective method practised for the control of this 

 and other pests of the sugar cane in the Hawaiian Islands. 



In the selection of canes resistant to attacks of leaf- 

 hopper, the Yellow Caledonian has been found to be the most 

 valuable of all the varieties tried. 



The use of other crops in rotation with sugar-cane is 

 strongly recommended. Sugarcane has been the principal 

 crop in the Hawaiian Islands for many years, and certain 

 areas have been planted continuously in that crop for twenty- 

 five years. Other crops should be grown, either for market or as 

 green dressings, for rotation with sugar-cane. The practice 

 of burning the trash results in the loss of great quantities of 

 organic matter: this can best be replaced by a green dressing 

 crop, and if for this purpose a leguminous crop be used, not 

 only organic matter, but an amount of nitrogenous plant 

 food, will be added to the soil. 



It has been estimated that the injury caused by the leaf- 

 hopper to the sugar-cane industry in the Hawaiian Islands 

 during 1903 and 1904 amounted to $3,000,000. It is likely, 

 however, that other pests, and certain fungus diseases, were 

 responsible for a portion of this loss. The leaf- hopper was 

 by far the most important of the pests, and this insect, also, 

 was responsible to a large extent for the severity of the 

 attacks of the rind fungus {Jfe/ancoiiium saccliari), since the 

 incisions made by the female leaf -hoppers in egg-laying, and 

 the punctures of these insects of all ages made in feeding, 

 offer the most ready means of access for the fungus to the 

 interior of the cane. Any practice which results in the re- 

 duction in the numbers of the leaf-hoppers will have a very 

 beneficial efl'ect in connexion with the occurrence of the rind 

 di.sease. 



Among natural enemies, many predaceous insects, native 

 to the Hawaiian Islands, at the time of the severe out- 

 break of leaf -hoppers in 1903 and 1904, found in this pest 

 a source of food, and undoubtedly aided in reducing its num- 

 bers. Parasitic insects were introduced from America and 

 from Australia. The mosc important of the introduced species 

 were certain egg parasites from Australia, which is the ori- 

 ginal home of the leaf-hopper. 



The practice of burning the trash results in the destruc- 

 tion of many beneficial insects, and in consequence of this, it 

 is still found necessary to propagate the parasites under arti- 

 ficial conditions, and to distribute them in the fields as the 

 attacks of the leaf -hopper are commencing. 



The Hawaiian sugar-cane leaf-hopper does not occur on 

 the continent of North America. The insect is closely related 

 to the corn leaf-hopper, Dicranotropis [Delphax] iiia'idis, 

 which occurs in the Southern States, and has been recorded 

 from the West Indies. 



The West Indian species, De/plui.r sacc/tarirora, is 

 a leaf-hopper attacking sugar-cane; but this insect does not 

 often occur in sufficient numbers to cause any serious loss. 



The sugar cane borer of the Hawaiian Islands is a weevil 

 borer, related to the weevil borer which is of common occur- 

 rence in the West Indies. It is the second in importance of 

 the sugar-cane pests in those islands, and in addition to the 

 sugar cane it attacks several palms, and the papaw (C'arica 

 Papaya). 



The eggs are laid beneath the epidermis of the cane 

 stalk; and the larva lives in the tissue of the cane, often com- 

 pletely destroying the entire interior, even when there is no 

 external evidence of injury to be seen. The life of the borer 

 within the stalk lasts seven weeks. The pupa is formed 

 within a cocoon made from the fibre of the cane in the stalk. 



