26 REPuirr of office of experiment stations. 



tlu»v Imvo been found very efficient for the control of the rust mite, 

 purple scale, and otlier pests. Some modiiications had to be woiked 

 out in the prescribed formulas to adapt them to Porto Rican condi- 

 tions. Experiments have been taken up in cooperation with several 

 planters for the conti'ol of tlie larva' of one of the Lachnosterna 

 beetles. These larva' are very destructive to the roots of sugar cane, 

 and it was found that lime applied about the stools of cane seemed 

 to reduce the number of grubs, the female beetles apparently being 

 repelled by the conditions where lime was applied. The life history 

 of this insect as it occurs in Porto Ilico is being studied. The ento- 

 mologist carried on some exi^eriments on the fumigation of tobacco 

 in the warehouse to prevent injury by beetles, and has devised a 

 method of fumigation with potassium cyanid by which large amounts 

 of tobacco can be treated. Breeding work with Telenomus monili- 

 cornis, the parasite of the eggs of the tobacco hornworm, has been 

 continued, and large numbers of the parasites w^ere distributed not 

 only in Porto Rico, but were sent to the Bureau of Entomology of 

 this Department for distribution. Other miscellaneous entomological 

 experiments are in progress. 



Much of the time of the chemist was taken up in the installation 

 of the laboratory and in miscellaneous analytical work on guanos 

 and other fertilizers, soils, waters, and other material. The princi- 

 pal investigations of this department have been on soil disinfection 

 and plant nutrition. The injection of carl)Cn bisulphid was found 

 very efficient for the control of abnormal soil conditions which result 

 in the so-called sick soils, but the cost of the treatment proved pro- 

 hibitive. Experiments are in progress with some of the cheaper 

 germicides to see whether they will not prove equally valuable in 

 correcting the soil conditions. A study was begun of pineapple 

 soils to determine the cause of failure on the part of plants when set 

 in certain types of soil. This is closely connected with the studies 

 in plant nutrition in which an excess of lime was found to result in 

 a chlorotic condition of the plants. To overcome some of these 

 troubles the lime and magnesium ratio for various crops and soils 

 is being studied. 



The experiments at the coffee substation are progressing. Some 

 of the varieties of coflfee introduced from Java, Arabia, and elsewhere 

 have come into bearing and their characteristic qualities are found 

 unimpaired when grown under Porto Rican conditions. All the 

 seed produced by these plants have been distributed, and the requests 

 for seeds of the better varieties far exceeded the supply. In several 

 instances the coffee expert has aided planters in the construction and 

 planting of seed beds. Experiments with windbreaks about and 

 through coffee plantations have demonstrated their value, and trials 

 have been begun of two native species of plants for this purpose. 



