POPULATION FLUCTUATION OF CERTAIN PESTS AND THEIR ASSOCIATED PREDATOR INSECTS ON SUGAR BEET IN SHARKIA GOVERNORATE, EGYPT

Abstract

The present study was conducted on the sugar beet insect pests, Cassida vittata, Pegomia mixta and Myzus persicae, their related natural enemies inhabiting sugar beet fields of Zagazig district in Sharkia Governorate, Egypt during two successive growing seasons (2008/2009 and 2009/2010). In the first season, two peaks of Cassida vittata larvae and adult represented by 587, 695 larvae/50 plants and 243, 240 adult/50 plants, respectively. While, in the second season, two peaks for larvae were recorded and represented by 664, 2250 larvae/50 plants respectively. In case of adult stage, four peaks were recorded and represented by 64, 216, 420 and 616 adults/50 plants, respectively. The sugar beet fly Pegomia mixta started appear on the plants on the 1 st week of December with few numbers (129 eggs/50 plants). Two peaks of eggs were found on sugar beet plant of the two seasons. These peaks were recorded and represented by 537, 446 eggs/50 plants, in the first season. In the second season, these peaks were recorded and represented by 558, 543 eggs/50 plants. As for larval instars, it was noticed that it had two peaks of 487, 533 larvae/50 plants, in the first season and the number of larvae reached 736 and 697 larvae/ plant in the second season. One peak of Myzus persicae on sugar beet plant during the two seasons. This peak was recorded and represented by 2945 insects/50 plants and 3089 insects/50 plants, respectively. About natural enemies Coccinella undecimpunctata and Chrysoperla Carnea appeared in November, 2008/2009 and 2009/2010 but Paederus alfierii was observed during January in both seasons. The peaks of the studied predacious insects occurred in February, of the first season almost similar trend was obtained during the second season of study and represented by 270, 522, 132, 159, 302 and 395 predacious, respectively.