14 CIRCULAR 349, U. S. DEPARTMENT OF AGRICULTURE 



of packing under various conditions. The special technic employed 

 and the results of these experiments have been siunmarized by Stone. 7 

 In the part of the experiment reported here, alluvial sand (similar to 

 that used in the 1932 experiment) and common soil of the locality 

 were used. Both were screened to eliminate foreign material and 

 large lumps. The results of part of the experiment are shown in 

 figure 1. 



From the results of this experiment the following conclusions can 

 be drawn: 



The soil used in the experiment possessed better packing qualities 

 than the sand. 



The finer the sand or soil, the better it packs. 



The moisture content of the material is by far the most important 

 factor. 



It appears that the force applied to a packing implement, and not 

 the weight of the implement itself, is important. Xo marked differ- 

 ence in results was observed when a 25-pound implement was substi- 

 tuted for one weighing 15 poimds and having the same packing 

 surface. 



Double packing is advisable, not only because of the added effi- 

 ciency, but also because all parts of the surface of a pit are more 

 certain to be treated in field practice. 



The effect of packing decreased gradually from the top to the 

 bottom of the pits, although some irregularities in the decrease were 

 observed in occasional levels in nearly all pits. 



SUMMARY 



Previous depth-of -burial experiments have been inconclusive, owing 

 to the fact that successful emergence of adults has taken place from 

 fruit buried 18 inches, the greatest depth tried. 



In the experiment of 1931, adults of Anastrepha ludens emerged 

 from pits 18 and 27 inches deep in the unpacked series. Xone emerged 

 from the eight pits hi the packed series. 



The soil of 7 pits of the unpacked series and 6 pits of the packed 

 series was examined for insect material. It was found that larvae of 

 Anastrepha ludens passed through the soil for considerable distances, 

 in some instances, before pupating. The greater number, by far, 

 pupated close to the fruit in the bottoms of the pits. 



It is suggested that, to prevent the emergence of any flies, infested 

 fruit be covered with at least 4 feet of sou if the soil is not packed. 

 TVnen packed, burial at a depth of 18 inches should be sufficient. 



In dry periods following rains there was a tendency for fissures to 

 open at the edges of the pits when soil of the adobe type was used in an 

 experiment. 



Burrowing insects make passages in the soil through which fruit fly 

 adults might escape. 



Burial pits should be examined occasionally to make sure that no 

 flies are being allowed to escape through fissures that are formed in 

 the soil or by passages made by other insects. 



In the experiment of 1932 no adults emerged from IS inches of 

 packed wet and dry sand placed above infested fruit. One dead larva 



: Stone, W. E. comparative efficiency of single and double PACKING WITH 15 AND 25 POUND 

 PACKERS ON SCREENED AND UNSCREENED, WET AND DRY SAND AND SOIL IN FRUIT-DISPOSAL PITS. 1934. 



(L npublished report.) 



