A/) ^^M^ 



AIlS-lOl 



UMITED STATES DEPARTcSin' OF AGRICULTURE r-r 



Agricultural Marketing Service - \ 'd> V\ A . .. . 



^ferketing Research Division \^^m:^^^ ^^K. RECOPO 



^ JUL 2 4 IS:- 



oTUDIES ON SEPARATION OF ^.^JEEVIL-II'IFESTED ^FROM-'Epartment of / 

 MCNINFESTED VJI-IEAT BY FLOTATION 



Gailen D. VJliite, Stored- C^ain Insects Laboratory-' , 'fenhattan, Kans. 



SU:€-^IARY 



Samples of hard red winter x^heat, in.th 12 percent moisture content 

 and infested vjith the rice weevil, were immersed in solutions of sodium 

 silicate vri.th specific gra\'ities ranging from 1.0^0 to 1,350, in de- 

 tailed laboratory studies to separate weevil-infested from noninfested 

 wheat by flotation. In solutions ;d.th specific gravities of 1.190 or 

 below, about ^0 to 70 percent of the infested keinels were separated 

 from the grain sa-Tiple without any sound kernels floating. At a speci- 

 fic gTavity of 1.3^0, all infested kernels floated, but 6I|. percent of 

 the sound kernels floated also. Each sample was X-raj'-ed to determine 

 the exact number of infested kernels contained in it. 



When infested samples were immersed in a 2- layered liquid in which 

 a sodium silicate solution i-Tith a specific gravity of l.loO was floated 

 on a methyl chloroform-kerosene solution irLth a specific gravity of 

 1.300, the top floating layer contained mostly kernels infested vjith 

 advanced stages of larvae, the second floating layer contained a mix- 

 ture of kernels infested t-rith early- stage larvae and lightweight sound 

 kernels. The nonfloating residue was nearly all sound kernels. 



It is suggested that the immersion of samples of commercial wheat 

 in a solution wdth a specific gravity somewhere betvreen 1,190 and 1,0^0 

 could be used to gave a fairly accurate estimate of the intensity of 

 infestation present on the basis that if more than one kernel contains 

 advanced- stage larvae, this fact would be evidenced by floating kernels. 



i/ The Stored-'Srain Insects Laboratory is one of the field stations 

 of the Stored-Product Insects Section, Biological Sciences Branch, 

 Marketing Research Division, Agricultuj'al Ilarketing Service, U, S. De- 

 partment of AgTiculture. 



I-larch 1956 



