Abstract:
This study shows the life table of the predator
Hippodamia variegate during the period January – March
2004. The predator was collected from Alfa alfa forage field
at Shambat Demonstration Farm. The predators were
confined with a number of aphids in cylindrical cages 9 cm
in diameter covered with a piece of cloth held in position by
a mean of rubber band. Eggs of the predator were collected
at frequent times for the study purposes.
A cohort of predator eggs (200 eggs) were placed on
leaves of okra, eggplant and potato crops to follow-up and
record the life table data until the adult stage. From the
emerged adults, ten males and ten females were selected and
confirmed each pair separately to follow the rest of the life
table's data.
The average net rate of reproduction (Ro) was
(182.245), time generation (T) was (17.61), the innate
capacity for numerical increase (rm) was (0.296) and the
doubling generation time (DT) was (2.331) in potato crop.
In okra crop the (Ro) was (145.29), (T) was (16.593), (rm)
was (0.3) and (DT) was (2.3). In eggplant the (Ro) was
(122.631), (T) was (18.698), (rm) was (0.257), and (DT)
was (2.68).
The highest (mx) was recorded in okra leaves and the
lowest in eggplant. The female longevity (Lx) was high in
okra crop (0.5) compared to value obtained from the potato
crop (0.140).
3
Following the development of the immature stages, the
mortality rates were found to be 40 %, 24 %, 15 % and 12 %
among the eggs, larvae, pupae, and adult stages respectively.
From these results, the highest death rate was mainly
recorded among the immature stages. Highest rate of egg
laying was recorded in Datura leaves (31.66 eggs) followed
by Ushar leaves (30.1 eggs) and lastly pumpkin leaves (20
eggs).
The field surveys of population, A. gossypii and the
predator H. variegate was carried out in three vegetable
crops. The result indicated that the highest population of the
Aphid was recorded in okra crop (116.13 adults) and the
lowest was on eggplant (0.6 adults). Similar data about the
population of H. variegate showed that okra plant has the
highest density (0.86 adults) compared to potato.
4
