Plant parasitic nematodes infesting citrus orchards in Sharkia governorate, East Delta, Egypt with speical reference to Tylenchulus semipenetrans cobb [electronic resource].

Includes reference.

Nine genera of stylet-bearing nematodes were found infesting citrus orchards in Sharkia Governorate East Delta, Egypt. Tylenchulus occurred in 95.81% of the total examined samples with population density of 1619.66 nematodes/250gm soil. The identified genera varied in their frequency of occurrence and population from one county (district) to another. For instances, number of the citrus nematode T. semipenetrans was obviously lower in heavy clay soil of Minet El-Kamb compared to higher numbers in light sandy soil of Abou-Hammad, Belbies and Fakous. On the other hand, occurrence and population density of the identified genera infestation navel orange were compared under three irrigation systems namely. drip, sprinkler and surface irrigation systems. The citrus nematode, T. semipenetrans was found with high value of percent frequency of occurrence in sprinkler followed by drip and surface irrigation system. On contrary, high population density was detected in drip system, followed by sprinkler and surface irrigation systems. Seasonal population density of T. semipenetrans infestation navel orange in sandy soil revealed that there were two peaks or suitable periods for development and reproduction of the nematode. The first peak was situated in February, while the second one was took place in November. The peak of November was very high as compared to that of in February. Moreover, vertical and horizontal distribution of T. semipenetrans infecting navel orange under drip and surface irrigation systems showed that as the soil depth increased from 0-20 to 20-40 and 40-60 cm numbers of citrus nematode were significantly decreased under the two irrigation systems. Vice versa was true in horizontal distribution, since as the distance from tree trunk increased from 0-50 to 50-100 and 100-150 cm. Numbers of citrus nematode were significantly increased under the two irrigation systems, except slight increase was noticed when distance increased to 100-150 cm in drip irrigation system.

Summary in Arabic.

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