Population density of aphids and spider mites on cotton using three scouting methods and its relation to some biotic and abiotic factors

The present study was carried out at Sakha Agric. Res. Station during 2002 and 2003 cotton seasons to study the population densities of cotton aphid, Aphis gossypii (Glover), spider mites, Tetranychus spp. and their associated predators as well as prevailing climatic factors (daily mean temperature and relative humidity). The obtained results revealed that, in both seasons, the aphid population recorded the highest number during August using three techniques (complete leaf, one inch in the main vein of the leaf and one inch between the two main veins of the leaf). In each of the two techniques of scouting (complete leaf and one inch in main vein of the leaf), the highest peaks were recorded on August 4 and August 14 in the first and second seasons, respectively. While these peaks were recorded on August 18 and 7, in both seasons, in the case of one inch between two main veins of the leaf, The spider mite recorded the highest number during July for the three scouting techniques in both seasons, the highest peak was recorded on July 21 in complete leaf and one inch in the main vein of the leaf in the first season. While it was on July 14 in one inch between two main veins of the leaf in the first season and was on July 10 in the same method in the second season. Also, the population of associated predators recorded the highly number during July and August in both seasons. Positive significant correlation occurred between aphid and total predators only in the first season and spider mite in both seasons. In both seasons, the temperature induced insignificant effect on aphids and spider mites on the three scouting techniques except on aphids in the complete leaf and spider mites in one inch in main vein of the leaf for the first season. Relative humidity had significant positive effect only in the first season. Joint effect of predators and weathering factors was found remarkably high on the density of spider mites than aphids during the two seasons.