Abstract:
Experiments were conducted in 2001,2002 seasons at Gedarif
and 2002 at Damazin, to compare the efficacy of diazinon treatments
on the midge-susceptible and resistant sorghum cultivars for control of
sorghum midge, Stenodiplosis sorghicola (Coquillet)
(Cecidomyiidae:Diptera).
At Damazin, where the average midge density was high, 7.9
adult midge per head, diazinon treatments resulted in significantly
lower damage on the panicles of MCR/117 (16.5%) than on the
Korokoro cultivar(26%), when the same diazinon treatments applied
five and three times every three and five days respectively. Even
untreated, theMCR/117 cultivar exhibited significantly less damage
(4.5%) than Korokoro (13%) regarding diazinon treatments of five or
three applications at 3- and 5- days intervals. The untreated (control)
of MCR/117 significantly exhibited less damage than (29%) than
untreated (control) of Korokoro cultivar.
The MCR/117 cultivar treated three times every five days
exhibited significantly less damage (17.6% ) than Korokoro treated
five times every 3 days. No significant differences of midge damage
were found between diazinon treatments, 5 and 3 applications at 3 –5-
days intervals for midge-resistant and susceptible cultivars .The
results indicate that, at moderate to high level of midge density,
midge-resistant cultivars receive more protection from insecticide
applied three times at 5-days interval, when compared with midgesusceptible
cultivar treated five times at 3-day intervals.. No
significantly differences of percentage of yield loss were found
between treated with diazinon and untreated for both cultivars
Korokoro and MCR/117.
ii ii
At Gedarif, where midge density was low, average 1.9 adult
midges per head, the damage on the panicles of the MCR/117 was
about equal whether treated or not. The Korokoro cultivar treated five
or three times at 3- and 5- day intervals exhibited significantly less
damage than (control) (14 and 14.5%), respectively. The control of
Korokoro significantly exhibited more damage (20%) than the control
of MCR/117 treated three times every 5- days showed significantly
less damage (6.3%) than Korokoro treated five times every 3- day.
The percentage yield loss on Korokoro treated five times or three
times were significantly lower than the control (30 and 25%),
respectively. But between diazinon treatments of MCR/117 no
significant differences were found. The percentage yield loss on the of
control of Korokoro was significantly greater than the control) of
MCR/117 (27.6%). However, when comparison was made between
Korokoro and MCR/117 treated five or three times, no significant
differences occurred. The evaluation of results revealed that, when
variable diazinon applications were made at 50% panicle flowering
stage, and where midge density was high, the midge resistant cultivars
responded more efficiently to diazinon treatments in terms of
percentage yield loss, compared with midge-susceptible cultivars.
