Ecological studies on Tetranychus urticae, Aphis gossypii and associated spiders on cotton plants at Qalubiya and Beni-Suef governorates in Egypt

The population density of the two spotted spider mite, Tetranychus urticae Koch, the aphid, Aphis gossypii Glover and associated spiders was monitored throughout the two seasons 2019 and 2020 at Qaha, Qalubiya and Wasta, Beni-Suef governorates, Egypt. Obtained results revealed that T. urticae increased from mid-May to reach a peak in mid-August. A. gossypii was recorded with moderate number in mid-May and gradually increased to June. Associated spiders were recorded to peak in mid-July. The highest frequency of collected spider species were Thanatus albini (Audouin), Cheiracanthium inclusum (O.P.Cambridge), Dictyna innocens (O.P.Cambridge), Mermessus denticulatus (Banks), Pulchellodromus glaucinus (Simon), Ballus piger (O.P.Cambridge) and Synema diana (Audouin).The combined effect of weather factors on population dynamics of both T. urticae and A. gossypii were insignificant over the two seasons and locations in most cases. It had less significant effect once considered pests’ population dynamics than plant age. Plant age as third degree of polynomial (emulating host plant developmental stages) had much more significant effect. Influence of weather factors and plant age combined effect explained variance was 96.05, 94.52, 88.53, 83.49% for T. urticae and A. gossypii in the first and second season, respectively at Qaha location during the two seasons. Similar results were obtained for Wasta location. The combined explained variance was 78.85, 87.05, 84.88 and 92.49 for T. urticae and A. gossypii in the first and second season, respectively. Correlation results between spiders’ counts, T. urticae and A. gossypii over the two seasons and locations was inconsistent.