) ‫أنموذج ( أ ) الخاص برسائل الماجستير و اطاريح الدكتوراة ( اخر شهادة‬
University of Baghdad
College Name
College of Science
Department
Biology department
Full Name as written
in Passport
Hind Suhail Abdul hay
e-mail
hind442@yahoo.com
Career
Assistant Lecturer
Lecturer
Master
Assistant Professor
Professor
PhD
Thesis Title
Study the efficacy of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) in the
control of cabbage aphid, Brevicoryne brassicae (L.) (Homoptera:Aphididae)
compared with a pyrethroid insecticide.
Year
2011
This study was conducted to examine the effectiveness of the predator Chrysoperla
carnea (Stephens) (Neuroptera: Chrysopidae ) in controlling nymphs and adults of
Abstract
cabbage aphid, Brevicoryne brassicae (L.) (Homoptera: Aphididae) under both laboratory
and field conditions. Also testing of the possibility in combination with Deltamethrin
insecticide was studied as an integrated control program of this insect.
Results showed high efficiency of the predator to attack and consum nymphs and
adults of cabbage aphid. Predation efficiency increases with the progress of the larval
stages up to the third (last) which was the most voracious .The 1st instar nymphs consumed
by the larvae of the predator were 47,80,181.67 nymphs ,with predation rate 14.71% ,
23.75% , 50.13% for 1st ,2nd and 3rd larval instars .
For the purpose of predicting the predators҆ efficiency in the field the limiting factors on
the attack was studied. Results showed a decreasing time for prey consumption with the
advancement of the predator age. It was for 1st larval instar 7.9 , 6.1 , 5.5 , 4.8 and 3.6
times more than for 3rd larval instar, when preying on the four nymphal instars and adult
stage of B.brassicae (L.),respectively. Also the movement and search area of the predator
were accelerated within a specified time. This enables the predator to cover a wider area ;
the speed was 5430 cm /hr., for 3rd larval instar ,which amount to an area of 814.5cm²/hr.,
as compared with a speed of 526.4cm/hr., and an area of 65.64cm²/ hr., for the 1 st larval
instar .
Regarding the effect of prey density on the numerical response of the predator, it was
found that larvae of the predator had a distinct ability to survive in conditions of
) ‫أنموذج ( أ ) الخاص برسائل الماجستير و اطاريح الدكتوراة ( اخر شهادة‬
inadequate feeding. Increasing the amount of food consumption in the larval stage had a
positive impact on the survival rate of larval instars , accelerated development and
longevity of adults with a high sex ratio in favor of females as well as increase oviposition
period and fecundity.
Functional response was measured by offering varying densities of cabbage aphid for
each individual predator. C.carnea showed type–II functional response , when the number
of prey killed approaches asymptote hyperbolically as prey density increases (declining
proportion of prey killed or the inverse density dependent) till it reached the stability stage
determined by handling time and predator satiation . Also, the values of attack rate and
handling time changed with age progress for both predator and prey. It has been observed
an increase in the attack rate and reduction in handling time with the progress of the
predator age when feeding on a particular nymphal instar. The attack rates of the predator
was 1.779,3.406 and 4.219 ,while handling time was 0.015,0.010 and 0.008(days) for
1st,2nd,3rd larval instars respectively, when fed on 1st nymphal instar. Also attack rates
decreased and increases handling time with the progress in the prey. The attack rates were
1.779,1.392,1.096 and 1.059 ,due to an increase in size of the predator and in the growing
efficiency in hunting the prey as well as in the increase in size of the prey and in
developing its ability to defend itself and escape.
The results also showed that the increase in population density of the predator led to
increasing conflicts and encounters among predators in the search area ,this reduces the
encounter with the prey, as well as increased cannibalism, thus, reflected negatively on the
efficiency of predator search.
Assessing the effect of Deltamethrin on the predator and prey on the basis of LC 50
values, laboratory data have indicated a positive correlation between these values and the
progress of B. brassicae (L.) life cycle . The adults were more resistant to the insecticide
than the nymphal instars . The LC50 and LC90 values for the 4th nymphal instar were 1.8
and 1.6 times more than 1st instar; also, the alatae were more susceptible than the apterae
for Deltamethrin .
Deltamethrin showed selectivity among C.carnea stage, where LC50 for the 1st larval
instar was 4 times for the recommended field concentration. Our results indicate that it was
more toxic to eggs and adults than larval instars,which increased its tolerance as age
progressed . The survey also proved that all concentrations against cabbage aphid were
safe for the predator after 24 hours
Field study was conducted to investigate the toxicity of Deltamethrin against cabbage
aphid .Population density was determined before spray, then mortality was followed at
intervals of : 1 , 4 , 7 , 15 , 21 and 30 days after spray .The results indicate a very high
) ‫أنموذج ( أ ) الخاص برسائل الماجستير و اطاريح الدكتوراة ( اخر شهادة‬
toxicity of about 81.9% kill after 4 days, then reached a maximum of 90.9 % after a
week, and 79.3% after 15 days.
Also, biological control was tested by releasing predator on B. brassicae (L.).
Successful control was achieved reaching to 55% after 14 days, then gradually rose to
80.9% and 89.5% after 21 and 30 days respectively. Finally, we recommend the use of C.
carnea as a prime candidate for mass release as having a high potential ability to control
cabbage aphid .