754 ANNUAL REPORTS OF DEPAliTMEKT OF AGRICULTURE. 



The chemical department during the past year has carried out a 

 hirge amount of analytical work on new varieties of sugar cane, 

 waters, limestones, guanos, and other fertilizing materials. The 

 research work has been chiefly devoted to studies on soils and plant 

 nutrition. Among the subjects of soil studies were the formation 

 of calcareous hardpan, injury by alkaline waters, lime requirements 

 of soils, etc. A large amount of work has been done on the causes 

 and means for correction of the chlorosis of pineapples in certain 

 districts of the island, Avhich appears to be due to unfavorable soil 

 conditions. In connection with this investigation a study has been 

 begun on the lime-requiring plants and those which do not thrive 

 in the presence of lime. Some studies on the lime and magnesium 

 ratio for plants have been begun, and a series of water cultures is in 

 progress. The work on the sick soils due to superabundant bacteria 

 described in the previous report has been continued and field experi- 

 ments on soil disinfection with different chemicals are being carried 

 out. If chemical disinfection proves too expensive it is believed that 

 frequent deep plowing, preferably w^th a large steam plow, will 

 correct the evil, through the aeration of the soil and the exposure of 

 the organisms to the action of the sun. 



The entomologist has continued his studies on the insect pests of 

 citrus trees and has prepared a bulletin describing the principal 

 insects and suggesting means for their control. In the preparation of 

 this bulletin it was necessar}^ to test the methods of combating insects 

 in other regions, and in many instances some modification in the 

 formulas for preparation of the insecticides or their application was 

 necessary to adapt them to Porto Rican conditions. By fumigation, 

 spraying, and the introduction of wind-breaks about the trees, so as 

 to permit the rapid growth of beneficial fungi, it has been found prac- 

 ticable to keep the insects in check on most orchards. An investiga- 

 tion has been begun on the injury to coffee trees by ants. The ants 

 live preferabh'^ on the shade trees, but colonies w^ere found on coffee 

 trees, where they do some damage. Experiments with repellants have 

 shown that some may be found effective. An extensive study has 

 been made of Lachnosterna sp., an insect resembling the INIay beetle. 

 Its larvae are particularly troublesome in cane fields. The beetles feed 

 principally on certain weeds, and spraying the weeds with arsenate of 

 lead was found to destroy the most of the beetles. Carbon bisulphid 

 injected into the soil destroyed the ginibs, and experiments are in 

 progress with lime and other fertilizers to prevent, if possible, the 

 depositing of the eggs in the cane. 



Through the activities of the station a deep interest has been 

 aroused in bee keeping, and a number of nuclei of broods have been 

 disposed of to go to coffee plantations. At one time the station was 

 instructing 15 persons in the handling of bees, methods of raising, 

 and the production of honey. 



The plant pathologist has studied the diseases of a number of 

 economic plants; among them are those occurring on coffee, cacao, 

 pineaples, citrus fruits, sugar cane, and bananas. It has been found 

 possible to control the coffee-leaf blight by spraying just before the 

 beginning of the wet season. Experiments are in progress looking 

 to the control of the coffee disease due to Stilhum flavidum. The 

 effect of trenching about trees to prevent the spread of a root disease 

 is being tried. The experiments on soil disinfection for the pre- 



