ECOLOGICAL STUDIES ON NATURAL ENEMIES ASSOCIATED WITH APHIDS ON ALFALFA CROP AT FAYOUM GOVERNORATE, EGYPT.

Document Type : Research articles.

Author

Department of plant protection, Faculty of Agriculture, Fayoum Univ., Egypt.

Abstract

The presnt study was carried out during 2012/2013 and 2013/2014
alfalfa seasons. The aphid species, Aphis craccivora Koch, Therioaphis trifolii
Mon. and Acyrthosiphon pisum Harris were found in both study seasons, A.
craccivora and T. trifolii were prevalent. The dominant predators were
Coccinella undecimpunctata L. reaching 32.3% of predators population in the
first season, Chrysopa carnea Stephens and Orius sp. which reached 80.1% in
the 2nd season. Aphid fungal infection rate (8.4 to 8.7%) was higher than the
rate of aphids parasitized (3.6 to 6.1%).The total death occurred by parasitism
and fungal infection ranged from 12.3 to 14.5 % of the total collected aphids.
C. undecimpunctata had 5 peaks per season with highest peaks in the 1st week.
and last week of Dec for both study seasons, respectively.The highest peak of
C. carnea was recorded in the 2nd week of April, while the highest population
density of Orius sp. was in spring. Aphid parasitism occurred during two
periods of activity in both seasons. The highest peaks of fungal infection were
8.67 and 10.0 infected individuals / 10 stems of alfalfa in the 2nd and 4th weeks
of Dec. The results obtained from this study showed that fungal infected aphid
and C. undecimpunctata population were positively correlated with aphid
population and %RH, while they negatively correlated with mean temperature.

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