Fig. 4 describe the relationship between final rice
temperature and mortality of adults (MA) and eggs (ME),
respectively. Adults and eggs suffered 100% mortality when rice was heated to above 55 and 541C, respectively,
by microwave. Halverson (1999) compared lethal temperatures for pupae, young larvae and eggs of rice weevils in wheat treated with extremely high-frequency (EHF) and
super-high-frequency (SHF) microwaves, finding that eggs
were more thermotolerant than young larvae and pupae.
As microwave frequency increases, the depth of penetration decreases (Nelson, 1996), so eggs of rice weevils may
still have survived inside rice kernels in Halverson’s study.
A model describing the thermal death kinetics for adults
and eggs at different rice temperatures is established by Eq.
(3) as follows
?A
T
1?T
0
T?T
0
??m ðTXT1Þ;
M¼e ðT0oToT1Þ;
M¼0 ðTpT0Þ;
8
where T0(1C) is lethal rice temperature (the temperature at
which eggs or adults begin to be killed) and T1
(1C) is the
rice temperature when eggs or adults suffered 100%
mortality. The constant is the susceptibility factor,
which reflects how easy the insects were to kill. The
constant m is a coefficient fitted to the model.