INSULAR EXPERIMENT STATIONS. 27 



island, which appears to be due to unfavorable soil conditions. It 

 appears that a content of more than 2 per cent of calcium carbonate 

 in Porto Rican soils renders them unsuited for the gi'OAving of inne- 

 apples. Treating the chlorotic plants with iron sulphate resulted in 

 restoring the normal green color to the leaves and in stimulating the 

 growth, but it is doubtful whether such treatments can be made com- 

 mercially profitable. In connection with this investigation a study 

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

 thrive in the j^resence of lime. In view of the results of these investi- 

 gations it is recommended that other crops, as tobacco, coconuts, 

 pigeon peas, etc., be planted where the proportion of lime is found 

 injurious to pineapples. Some studies on the lime and magnesium 

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

 in progress. 



The entomologist 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 bul- 

 letin it was necessary to test the methods of combating insects in other 

 regions, and in many instances some modifications 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 windbreaks about the trees, so as to permit 

 the rapid gi'owth of beneficial fungi, it has been found practicable 

 to keep the insects in check on most orchards. An investigation has 

 been begun on the injury to coffee trees by ants. The ants live pref- 

 erably on the shade trees, but colonies were found on coffee trees, where 

 they do some damage. Experiments with repellents have shown that 

 some may be found defective. An extensive study has been made of 

 Lachnosterna sp., an insect resembling the May 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 grubs, and experiments are in progress 

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

 of the eggs in the cane. A parasitic mite has been found on the 

 larvae of the beetle, and its work is being watched with great interest. 

 Studies have also been made of the insects attacking guavas, and the 

 life history of a number of species is being vrorked out. Through the 

 activities of the station a deep interest has been aroused in beekeep- 

 ing, 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 entomologist made a visit to Cuba during the year to 

 compare some of the insect problems of that island with those in 

 Porto Rico. 



