Distribution and losses of Tylenchulus semipenetrans in citrus orchards on reclaimed land in Egypt

Abstract

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.

Managing nematodes in Egyptian citrus orchards

“…Cheap labor, geographic location, Mediterranean climate, and fertile soils have granted Egypt a high rank among citrus producer countries (Abd-Elgawad et al 2016). It is expected (Omar and Tate 2018) that Egypt will remain the first or the second largest exporter of fresh oranges in the world and the sixth largest orange producer (Fig.…”

“…Yet, the expansion via wide desert reclaimed land entails the danger of growing citrus seedlings infected with plant-parasitic nematodes (PPNs) especially the citrus nematode (Tylenchulus semipenetrans). The implication is that citrus growth and yield is threatened by the nematodes which invade the newly planted area via infected seedlings, organic fertilizers, plant materials, irrigation, and machinery (Abd-Elgawad et al 2016). Also, mulching virgin soil with fertile, but probably nematodeinfested, silty soil from the Nile Valley, to improve the soil quality, before planting possible infested material may aggravate the infection (Abd-Elgawad and McSorley 2009).…”

“…Also, mulching virgin soil with fertile, but probably nematodeinfested, silty soil from the Nile Valley, to improve the soil quality, before planting possible infested material may aggravate the infection (Abd-Elgawad and McSorley 2009). Over time, the nematode populations develop and reproduce rapidly and progressive increases in citrus yield losses are assumed (Abd-Elgawad et al 2016).…”

“…Few PPN species, however, have proved to be of economic importance. Except Tylenchulus semipenetrans, PPNs known to be capable of damaging citrus are very limited in distribution in Egypt (Abd-Elgawad, 1992a, b;Korayem and Hassabo 2005;Abd-Elgawad et al 2016) and elsewhere (Duncan 2009;Shokoohi and Duncan 2018). This is due either to edaphic conditions or to the natural distribution of a particular PPN species.…”

“…Therefore, agricultural practices should typically tackle all yieldreducing factors which would benefit sustainability evaluation in citriculture. Although the magnitude of nematode damage to any crop is related to PPN species, densities, and favoring conditions, there is consensus on the supreme importance of T. semipenetrans relative to other PPNs on citrus in Egypt (Abd-Elgawad, 1992a, b;Korayem and Hassabo 2005;Hammam et al 2016b;Abd-Elgawad et al 2016). This review throws light on the significance of the citrus nematode and provides a way forward for updated control tactics of the most common and damaging nematodes associated with citrus trees as well as general management strategies to maximize citrus yield and quality in Egypt.…”