Ecological and Biological studies on Tetranychus urticae Koch on Maize single hybrids at Gharbia Governorate.

Document Type : Original Article

Abstract

Field and laboratory studies were conducted on the two spotted spider mite Tetranychus urticae Koch throughout the year 2004-2005 at Gharbia governorate. The study included population fluctuations of T. urticae, Euseius scutalis and Pronematus ubiquitus on ten maize single hybrids (i.e. SC10, Pioneer30K8, SC122, SC123, SC124, SC129, YSC155, YSC3080, Bacheir13 and Watania4), and their relation with various meteorological variables. Susceptibility of different maize cultivars to the infestation with T. urticae revealed significant differences in moving stages, influence of leaf chemical components with T. urticae infestation was studied. The study revealed that the maize (YSC3080) single crosses recorded the highly significant susceptibility to infestation with T. urticae, recording averages of 235.21 and 274.50 moving stages/ 20 leaves,  while single cross (SC10) more resistant to mite infestation recording averages 115.54 and 118.46 moving stages/ 20 leaves during the two successive years, respectively. Mite  population  reached  its  peak  on  maize during season 2004 in early  September, while in the season 2005 it had two peaks, one in early August and the second in early in September,  for  all tested  hybrids.  Developmental times and reproduction rate of T. urticae were studied on leaves of four maize single crosses (i.e. YSC3080, Bacheir13, SC122 and SC10) at laboratory conditions of 28±2°C, 65±5 % RH and 16:8 L: D. Immature developmental time of T. urticae was longest on SC10 (6.7days) followed by yellow SC122 (5.5 days) than Bacheir13 and YSC3080 (5.1days). Longevity of T. urticae was 12.8, 10.4, 9.9, and 9.8 days on YSC3080, Bacheir13, SC122 and SC10, respectively. The highest net reproductive rate (Ro) was 18.79 females/ female/generation on YSC3080, and the lowest was 7.2 females/ female/ generation on SC10.

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