Influence of certain agricultural practices on the cowpea aphid, Aphis craccivora Koch, infesting broad bean crops and the relation between the infestation and yield of plants in upper Egypt.
The effects of certain agriculture practices, i.e. plant spacing, nitrogen fertilization levels, first irrigation and farmyard manure, on the infestation of 6 broad bean cultivars with Aphis craccivora were studied at El-Kawsar region, Sohag Governorate, Egypt throughout the 2003/04 and 2004/05 seasons. A. craccivora appeared from November until the second week of April. The faba bean cultivars showed varying susceptibility to infestation, and they were divided into the following groups: Giza 674 and Giza Blanka (susceptible); Giza 843, Giza 2 and Giza 40 (low resistance); and Giza 429 (moderate resistance). The numbers of A. craccivora were higher when 70 kg chemical nitrogen plus farmyard manure was applied compared with 40 or 55 units/feddan of chemical nitrogen during the two seasons. The population density of A. craccivora was significantly higher with lower plant spacing. The population density of A. craccivora increased significantly with an increase of nitrogen fertilization levels during both seasons. The broad bean plants sown on 10 cm and which received N at a rate of 90 kg/feddan harboured the highest numbers of A. craccivora compared with the other treatment (20 and 30 cm). The results showed that the broad bean plants which were irrigated at 56 and 63 days as a first irrigation harboured highly significant numbers of A. craccivora compared with the plants irrigated at 14, 21 and 28 days. These results also showed significant negative correlation between the infestation of A. craccivora and the yield of broad bean plants. [1 feddan = 0.42 ha].