THE CHANGES IN THE SEASONAL ABUNDANCE OF THE WHEAT LEAFMIN ER, AGROMYZA NIGRELLA (R 0 N DA NI) (DIPTERA: AGROMYZIDAE), AND RELATED PARASITES IN TWO DIFFERENT AGRO-ECOSYSTEMS

Sakha 69 wheat variety was sown on three successive planting dates at El- Gemmiza and Sids Agric. Res. Stations, representing tower and middle Egypt. The changes in the seasonal fluctuations and larval parasitism of Agromyza nigrella (Rondani) in 1995- 1996, 1996- 1997 and 1997- 1998 seasons was studied. Results obtained indicate that in­fested leaves, number of mines and live larvae were significantly higher In El- Gemmiza than in Sids. All considered parameters were significantly decreased by delaying sowing dates and markedly different from season to season. Multiple regression for the relationship existed between tem­perature and relative humidity and intensity of infestation, mine density and number of live larvae for the different seasons was worked out. Leaves and mines started in low numbers by late February, but increased gradually thus reaching its maximum levels by the third week of April, in both ecosystems. However, live larvae followed the same trend, but peaked early by the third and the fourth weeks of March in Sids and El­Gemmiza, respectively. Larval parasitism by eulophids Digfyphus isaea (Walk.) and PaigeNo spp. was 5.7% in Sids and 5.8% in El- Gemmiza. Un­der low larval parasitic activity, hot and dry weather conditions harbored an obvious decrease in infestation by wheat leaf miner A. Sella in Sick.