Entomopathogenic nematodes (EPN) can infect and kill a wide range of insect pests and are used as safe alternatives to chemical insecticides. Hence, a hypothesis was tested for obtaining EPN with high recovery frequency value and accurate distribution pattern based on combining four factors: favourable sampling method, time and site targeting and use of multiple extraction technique. As the extreme diversity of EPN sampling makes any generalisation from a given case study difficult, this functional sampling was limited to recovering EPN from citrus trees only in Egypt. It could both detect more EPN isolates and allow the application of different indices of dispersion to study their spatial distribution pattern. Therefore, stratified random and systematic sampling from weed-infested soil under tree canopy during the season of abundant insect pests was done, followed by multiple cycles of Galleria-baiting technique. Consequently, the nematodes were recovered from the seven surveyed groves (100%) and from 37 of 60 (61.7%) soil samples. The spatial distribution of these EPN isolates, previously identified as Heterorhabditis indica, was characterised using five dispersion indices, which were mainly a random rather than an over-dispersed distribution.
Four citrus orchards in Egypt were used in 2011 to study spread and losses of Tylenchulus semipenetrans based on a preliminary report of their infection in 2008. Soil and root samples indicated aggregated distribution and increase of nematode populations. The relationship between nematode number and lemon yield was described. When yield data of the mature groves were combined, we could construct other equations. The gain thresholds were 6.083 and 4.014 metric tons of lemon feddan−1 (= 4200 m−2) and the economic thresholds were 1810 and 141 second-stage juveniles (150 cm3 soil)−1 for cadusafos and oxamyl, respectively, based on the combined costs of nematode sampling and control to provide an actual estimate of a budget conscious choice. The use of healthy material is compulsory for tackling this problem in Egypt as a case in point. It entails setting up a citrus certification programme. Other phytosanitary measures to protect citriculture interests in Egypt are discussed.