Heat Requirements for the Development of the Black cutworm ...
Heat Requirements for the Development of the Black cutworm ...
Heat Requirements for the Development of the Black cutworm ...
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<strong>Heat</strong> <strong>Requirements</strong> <strong>for</strong> <strong>the</strong> <strong>Development</strong> <strong>of</strong> <strong>the</strong> <strong>Black</strong> <strong>cutworm</strong>, Agrotis ipsilon 119<br />
temperature increased. The means <strong>of</strong> incubation periods were 6.18, 3.67 and 2.81<br />
days at 20, 25 and 302C, respectively. Statistically, <strong>the</strong>re are obvious significant<br />
differences in A. ipsilon incubation period at all <strong>the</strong> tested constant temperatures.<br />
Table (1): <strong>Development</strong> <strong>of</strong> A. ipsilon eggs under different constant temperatures and its <strong>the</strong>rmal requirements.<br />
Temp.<br />
( °C)<br />
Incubation<br />
period<br />
(days ± S.E) Expect<br />
duration (days)<br />
Rate <strong>of</strong><br />
development<br />
%<br />
Expect rate <strong>of</strong><br />
development<br />
%<br />
20 6.18 ± 0.04 a 6.02 16.18 16.61<br />
to<br />
(˚C)<br />
Degree days<br />
(dd΄s)<br />
25 3.67 ± 0.18 b 3.79 27.24 26.37 11.49 49.6<br />
30 2.81 ± 0.02 c 2.77 35.71 36.14 51.8<br />
Average 51.3<br />
L.S.D 0.16<br />
The threshold <strong>of</strong> egg development was calculated and illustrated in Fig. (1);<br />
it was found to be 11.49C. The average <strong>of</strong> <strong>the</strong>rmal units in degree – days required<br />
<strong>for</strong> <strong>the</strong> completion <strong>of</strong> development <strong>of</strong> this stage was 51.3 dd's. The three observed<br />
values <strong>of</strong> eggs rate <strong>of</strong> development at <strong>the</strong> constant temperature range (20 - 30C)<br />
gave a remarkable good fit to <strong>the</strong> calculated temperature – velocity line having <strong>the</strong><br />
<strong>for</strong>mula Y = 1.95 x - 22.4 (Fig. 1).<br />
R a t e o f d e v(1/t e l ox1 p0 ) m0 e n t<br />
4 0<br />
3 5<br />
3 0<br />
2 5<br />
2 0<br />
1 5<br />
1 0<br />
5<br />
0<br />
r = 0 . 9 9 K = 5 1 . 3<br />
y = 1 . 9 x5 - 2 2 . 4<br />
0 5 1 0 1 5 2 0 2 5 3 0<br />
T e m p e r a t u r e ( ° C)<br />
F i g . ( 1 ) : T h e r e g r e s s i o n l i n e o f t h e r e l a t i o n b e t w e e n t h e<br />
r a t e o f d e v e l o p m e n t o f A . i p s i l o n e g g s a n d d i f f e r e n t<br />
Fig. (1): The regression line <strong>of</strong> <strong>the</strong> relation c o nbetween s t a n t t e m<strong>the</strong> p e rate r a t u r<strong>of</strong> e s development .<br />
<strong>of</strong> A. ipsilon eggs and<br />
different constant temperatures.<br />
Larval stage:<br />
Table (2) indicated that <strong>the</strong> average larval duration varied from 33.06 days<br />
at 20C to 15.81 days at 30C. The analysis <strong>of</strong> variance showed significant<br />
differences (P < 0.01) between <strong>the</strong> means <strong>of</strong> larval duration at all tested<br />
temperatures. The lower threshold <strong>of</strong> development (t 0) <strong>for</strong> <strong>the</strong> larval stage was<br />
10.63C as indicated in Fig. (2).<br />
The same Table showed that <strong>the</strong> average <strong>the</strong>rmal units required <strong>for</strong> larval<br />
developmental till pupation was 303.5 dd's as determined by <strong>the</strong> <strong>the</strong>rmal<br />
summation equation.<br />
52.6