﻿THE GEANARY WEEVIL 29 



The e£Fect of a moderately low temperature is to prolong the life of 

 the adult weevil. As already recorded by the writers (S), a few of 

 the weevils placed in an ordinary refrigerator with a temperature 

 that ranged between 50° and 60° F. lived for a period of 29 months. 

 They were almost inactive at this temperature but fed occasionaUy. 

 When kept at a temperature of 35° to 40° F. a few adults lived as 

 long as 111 days, whereas at temperatures ranging from 40° to 45° F. 

 adults survived for 105 days. A temperature of 30° to 35° F. proved 

 fatal to adults of the granary weevil after 73 days. A temperature 

 of 25° to 30° F. killed all adults within 46 days. At 20° to 25° F. all 

 adults were dead at the end of 33 days; at 15° to 20° F., at the end 

 of 14 days; at 5° F., at the end of 73^ hours. A constant tempera- 

 ture of zero proved fatal to adults of the granary weevil at the end 

 of an exposure of 5 hours. 



Twenty per cent of the eggs of the granary weevil survived an 

 exposure to a constant temperature of 30° F. for 28 days. Larvae 

 exposed to this temperature survived for 44 days. 



PARASITES 



The granary weevil is attacked by several parasitic Hymenoptera 

 while in the larval and pupal stages. The two most commonly 

 observed in North America are Aplastomorpha calandrae Howard and 

 Chaetospila elegans Westw., while LariopJiagus distinguendus Forst. is 

 apparently the most abundant parasite of the granary weevil in 

 Europe. Goodrich (5^), in 1921, wrote regarding parasites of beetles 

 infesting grain. 



A predacious mite, Pediculoides ventricosus Newport, frequently 

 attacks the egg, larva, and pupa of the granary weevil. 



CONTROL MEASURES 



Control measures consist chiefly in the use of heat, cold, and fumi- 

 gants. The use of heat, in the ordinary gram heating and drying 

 equipment on the market, seems not to be popular with gram dealers 

 since grain is purchased by weight and heatmg results in the loss of 

 moisture. A temperature of 118° F. to 120° F. for one hour or of 

 130° F. for 30 minutes kills all stages of the weevil actually subjected 

 to it. It should not be forgotten that the gram must be heated 

 sufficiently to allow the proper amount of heat to penetrate to the 

 insects concealed within. In quarantine work the Federal Horti- 

 cultural Board has found it advi8a})le to require that corn entering 

 this country from Mexico bo subjected to a temperature of 200° F, 

 for at least five minutes to insure fj-cnulom from insect pests. 



Dean (16) and Goodwin (33) hav(i published on heat control. 



Carbon disulphide is the only fiimigant at present in general use iu 

 the United States for killing wcc^vils in grain in bulk. When carbon 

 disulphide is used at th(! rate of from 5 to 15 pounds ])er 1,000 buslu^ls, 

 according tf) the tiglitness of th(^ crib, tlie granary w(M5vil can bo 

 kilhid in all stages. Carbon totrucliloridc! aloju^ and etliyl acetate- 

 carbon tctracliioridf! mixture (47) vjiry in efrcctivcncss and must bo 

 UHOj\ fj'om two to four times as strong as carbot) <lisul|)liid(\ The 

 ethyl acetat(!-curbon tctrucJilorKh' Jnixturc, however, is not entirely 

 satisfactory to the grain trade (jn account of an ochn- which this niLx- 

 ture may leave. 



