A STUDY ON THE INCIDENCE OF DIAPAUSE AND PARASITISM OF, PEGOMYA MIXTA VILLENEUVE, (DIPTERA: ANTHOMYIIDAE) IN KAFR EL- SHEIKH AND DAQAHLIYA GOVERNORATES.

Infested leaf parts with the sugar beet learminer,Pegornya mixta (Diptera: Anthomyiidae) were collected from untreated sugar beet, Beta vulgans L., fields in Governorates of Kafr EL-Sheikh (at Sakha and Bila) and Daqahliya (at EI-Simbahvein, Bilqas and Shirbin) during the period from December, 2004 and 2005 to April, 2005 and May, 2006. Rate and incidence of diapause and parasitism as well as emergencies of flies and parasitoids were determined. Incidence of diapaused pupae and parasitism by Opius nitklulator (Nees) (Braconidae) increased progressively and varied according to location and season. Diapause and parasitism were two times greater and somewhat higher at Kafr El-Sheikh than at Daqahliya with overall means of 41.8 and 21.5% as well as 20 and 19.1%, respectively. Such rates were 49 & 23% in (2004- 2005) and 17 & 21% In (2005- 2006). Rate of diapause ranged between 47- 69% at Sakha and EI-Simbalwein in 2004- 2005, 15- 27% at Shirbin and Bilqas In 2005- 2006 and 30- 66% at Bila In the second and the first seasons. The corresponding rates of parasitism were 8- 18% at EI-Simbatwein and Sakha, 18- 20% at Bilqas and Shirbin and 6- 25% :t Bila in the first and the second seasons. In both seasons, flies emerged earlier than parasitoids from active and diapaused puparia, whereas asynchrony was found between the adults of host and parasitoids either at its timing of emergencies or activity peaks. In both diapause seasons, majority (> 79 & 58%) of flies and parasitoids emerged from late October to late November and in January and were continued until mid February, respectively. In both active seasons, it were emerged in lower rates 8 and 3% during the second half of December and continued until the second and the first weeks of May with peaks of 32 and 37% in March, respectively. Interference between the timing of flies emergendes from diapaused and active puparia resulting in overlapping generations, whereas the population growth rate of parasitoids was lower than those of flies, which retarded the biological control, at the beginning of the season. To conserve and promote parasitoids, pesticides must be entirely avoided. Also, the bio- effectiveness of the parasitoids is Indicated by the decrease in emergence flies from diapausing puparia by applying deeply plowing and dropping kerosene at a rate of 30 liter / reckon = 4200 m² into irrigation water against diapaused pupae in the soil to reduce the population of the emerged flies of the first generation.