22 REPORT OP OFFICE OF EXPERIMENT STATIONS. 



The chemical investigations have been continued along lines pre- 

 viously described. The results obtained in the work with manganese 

 soils have added greatly to the knowledge of conditions which pre- 

 vail in these soils and indicate that the pineapple is exceptionally 

 sensitive to unfavorable soil conditions and can not be made to thrive 

 where from 4 to 5 per cent or more of manganese is present. Other 

 crops are less sensitive to manganese, among them sugar cane, corn, 

 and cotton. If it is especially desired to grow^ pineapples on manga- 

 niferous soils it has been found that the best results can be obtained by 

 planting the old stumps rather than the suckers and by fertilizing 

 heavily with phosphates. It appears from an examination that im- 

 proper drainage of soil is a conspicuous cause of some of the pine- 

 apple troubles in the district of Wahiawa. It seems certain that pine- 

 apples do not require as much water as has been formerly supposed, 

 and where proper drainage is supjolied pineapples can be successfully 

 grown in the presence of heavy rainfall. Data are being accumulated 

 for a general classification of Hawaiian soils, some of which exhibit 

 striking peculiarities. Localities are known where soils contain from 

 8 to 10 per cent of manganese, and in others there was found 20 per 

 cent or more of titanium. 



The most important feature of the entomological work during the 

 3'ear was the discovery of the Mediterranean fruit Q.y. Since this 

 discovery the pest has spread with remarkable rapidity, attacking 

 peaches, all of the citrus fruits, mangoes, peppers, guavas, figs, and 

 avocados. The discovery of this pest in Hawaii led to the establish- 

 ment of a quarantine on the part of California against Hawaiian 

 fruits, except pineapples and bananas. The station has taken part in 

 devising a plan for the control of this pest, which consists essentially 

 in the collection and destruction of fallen fruit, and the results of the 

 campaign are evident in the greatly reduced numbers of the fruit 

 flies. Studies have been made of the insect pests of corn and legum- 

 inous plants during the year, and a bulletin prepared on the insect 

 pests of corn. Some attention has been given to the subject of insect 

 parasites, and a parasite which destroys from 5 to 10 per cent of the 

 bollworms has been found. 



The horticultural investigations have been continued with tropical 

 fi'uits. During the past season a budding method has been j^erfected 

 for the avocado by means of which success is obtained on young trees 

 in from 85 to 00 per cent of cases, and by the top-working of old 

 trees in from 50 to 75 per cent of all cases. In addition, a successful 

 inarching method has been devised for rapidly testing promising 

 seedlings. As far as possible, all types of avocados found in Hawaii 

 have been collected and a system of classification and description is 

 being worked out. Studies show that the variation in flavor, size, 



