10 



JOURNAL OF AGRICULTUEE OF P. R. 



Experiments with manurial agents. 



To test the value of various fertilizers or manurial agents as 

 deterrents of the white grub an extensive series of experiments was- 

 eonducted. At first, trials were made on a limited scale with beetles 

 in confinement. Flower-pots containing soil and a small amount nf 

 fertilizer were placed in a cage with the beetles. Each pot liad a 

 different fertilizer mixed with the soil and the beeth's had tlie oppor- 

 tunity to burrow in the pot that was most attractive to them. In 

 this experiment advantage Avas taken of the haliit of the beetles of 

 hiding in the soil during the day. Examination was made of the 

 pots each day and a count of the beetles in eacli made. Thus at the 

 end of a Aveek the total number of visits per pot was known and some 

 idea of the repellent or attractive powers of each material could 

 be formed. 



After a number of tliese preliminary trials, an experiment was 

 conducted on a field seale witli certain of the manurial agents, to 

 determine tlieir effect on the yield and quality of the cane, as well 

 as their deterrent effect as exhibited over an entire growing season. 

 The results are shown in the tabulations that follow. 



In the fii'st experiment nine pots of soil, eaeh eontaining a small 

 amount of fertilizer, were placed in a cage with fifty beetles. Tlu' 

 following table gives the amount and kind of fertilizer in each pot. 

 and the number of beetles that visited each pot daily for a week : 



Experiment XII. — Bepellant Effect of Various Manurial Agents on May Beetles. 



In the experiment that follows the same materials were used and 

 in the same proportions. However, in this ease ten beetles were placed 

 in each pot and at the end of a. week the pots were examined anrl 

 the living and dead beetles in each counted. Thus some indication 

 of the killing power as well "as the repellant action was given. 



