20 BULLETIN 965, U. S. DEPARTMEITT OF AGRICULTURE. 



An inspection February 7, 1918, showed that some ants had colonized 

 in the cans, but in the absence of heavy rains the ants were continuing 

 largely in their ground colonies. A final inspection March 18, 1918, 

 showed that only 41 per cent of the cans contained nests, and these were 

 for the most part small. Many colonies were found in the ground 

 beneath the cans or even at the base of the trees near the cans; in fact, 

 in all cases the preponderance of ants in the orchard appeared to be 

 outside the cans. The cans were fumigated with carbon disulphid 

 immediately following the final inspection. An inspection of the 

 entire grove in May showed the ants as prevalent in the part over 

 which ant traps were distributed as in the check plot, thus demon- 

 strating the futility of ant control in California by the trap-nest 

 method recommended for Louisiana. 



A second experiment in an adjacent grove with 50 trap boxes 

 during the same winter gave no better results. 



The- success of trap nesting, as pointed out by Newell and Barber, 

 depends upon rainy weather. The winter of 1917-18 was a warm 

 and open one with light rains, and this resulted in ants being more 

 ' or less active in southern California throughout the season. It is 

 very probable that in a colder winter with heavy rains trap nests 

 would be more successful. Even under the most ideal conditions 

 for trap nesting, however, this method would be less effective and 

 more costly than the poisoned-sirup method later taken up in this 

 publication. . ,,; 



POISONED ilRUPS. 



Eradication is the ideal to be sought with any pest and particu- 

 larly does this apply to the Argentine ant. Once the ant is eliminated 

 from a grove, future effort can be restricted to protecting the borders 

 from invasion from neighboring property. The , most effective 

 method of eradication tried in California has been the use of a 

 poisoned sirup, which is eaten by the ants. For the most .part 

 arsenic in some form constitutes the toxic substance of such a poison, 

 although a few nonarsenicals have been used. 



In all orchard work small containers of tin or paraffined paper 

 were used, partly filled with sirup and hung one to a tree, the ants 

 entering through small holes in the sides. 



Chloeal Hydrate. 



Chloral hydrate was recommended by Horton ^ as the best poison 

 for orchard use. It is prepared as follows : . 



Make a siAip by stirring 8 pounds of granulated sugar in one-half gallon of cold 

 water until dissolved, making 1^ gallons of sirup. Then add 4J ounces of chloral- 



9 HOBTON, J. R. CONTROL OF THE ARGENTINE ANT IN ORANGE GROVES. U. S. Dept. AgT., Farmers' 



Bul. 92S, p. 19. 1518. 



