Jum 2, 1920.] Agricultural Gazette of N.S.W. 387 



Kiln-drying Maize^ 



With Notes on Heat for Controlling Weevil and 

 Sweating in Maize and Millet. 



V.'. B. GURNEY, Assistant Entomologist, and J. M. PITT, Assistant Inspector 



of Agriculture. ' 



Thesb notes are intended generally to indicate to farmers the value of hot- 

 air blast conditioners or kilns for the control of weevil and for conditioning 

 maize either for the market or for storage. They have the more particular 

 object, however, of describing the simple structure of a home-made kiln. 

 The kiln-drying of maize should appeal to growers, not only because it 

 pemtits of the early market being caught, but because the cultivation of 

 early varieties in certain districts, followed by early pulling, brings in its 

 wake numerous advantages in farm practice, as will be shown later. 



Before maize can be safely stored in silos, the moisture content needs to be 

 reduced to about 14 per cent., and to even a lower percentage if it is to be 

 tightly sealed up in tanks or other airtight receptacles. 



The danger of "tanked" maize sweating is well known to farmers, the 

 erratic results being due to the presence or absence of moisture sufficient to set 

 up sweating. Excess moisture encourages mould and decay, and at the same 

 time favours the rapid development of weevil and moth, which, be it remarked, 

 are entirely different species of insects, as also a dozen or more other insects 

 that quite commonly develop in and are destructive to stored maize. These 

 insects all pass through the egg.j grub, pupal and adult stages, and never, of 

 course, can be spontaneously generated, so that, if maize is free from insects 

 when sealed in insect-proof tanks, no development of these insects can occur, 

 whether the maize is comparatively moist or comparatively dry. 



Adult weevils are killed on exposure for two or three minutes to a 

 temperature of 1 20 degrees Fah. Moreover, if maize is placed in layers a single 

 grain thick and exposed for five minutes to a temperature of 171 degrees 

 Fah., the grain is heated to 1 30 degrees Fah., and weevils present are destroyed . 

 We see, therefore, that exposure for longer periods of thicker layers of maize 

 would heat the grain sufficiently to kill any weevils present. A hot-air 

 blast of 150 to 160 degrees Fah., and even 175 degrees for shorter periods, 

 may be applied to maize, without much effect on germination However, 

 maize in bulk is mostly intended for food, and smaller quantities intended 

 for seed might be treated by heat for longer periods at lower temperatures, 

 or else fumigated or treated with naphthaline. 



As it is imperative that maize stored in closed receptacles should be dried 

 sufficiently to prevent it sweating, it is only safe in practice to store maize 

 that has been well air-dried by standing in the field, or that has been stored 



