Phytoparasitica (1997) 25, p. 247 (Mor et al.)

M. Mor, S. Ben-Anat and Y. Spiegel (1997)
Tylenchulus semipenetrans, the citrus nematode, and Xiphinema brevicolle are present in the new citrus plantations in the Northern Negev
Phytoparasitica 25 (3), 247-247
18th Congress of the Israeli Phytopathological Society, February 3-4, 1997, Bet Dagan, Israel, lecture
Abstract: Citrus seedlings, purchased from 13 citrus nurseries located in the central part of Israel, have been planted in the northern Negev (southern part of Israel) since 1993, in areas where citrus had never been planted before. In 1996 we started to screen citrus nematodes in these areas in samples taken from an area of 75 ha. Fifty-four percent of the plantations were not infested with plant-parasitic nematodes, whereas the rest were infested with the citrus nematode, Tylenchulus semipenetrans: 22% at a low infestation level (up to 500 second-stage juveniles [J2] per g root); 18% at a critical level (up to 4,000 J2/g root); and 6% at a very high level (up to 20,000 J2/g root). Such a high population level just 3 years after planting, may cause much damage, because of the microorganisms which follow the nematodes' penetration to the root. These secondary pathogens induce slow decline of the trees - a phenomenon that has already been observed in these plantations. Agrotechnical conditions such as aerated soil, drip irrigation and optimal temperature during most of the year, accelerate the increase in the nematode population. Nematode-infested citrus trees are more susceptible to stress conditions such as dryness and salinity; therefore, the relatively high-saline water which is used for irrigation may also contribute to the severity of the damage incurred by the nematodes. In addition to the citrus nematode, the plantations are infested with other ectoparasites, such as Xiphinema brevicolle (20 nematodes/g soil), which was found in 3% of the area screened. The optimal conditions mentioned above for the development of the citrus nematode, are suitable also for that of this ectoparasite species. Under greenhouse conditions, after 8 months, top fresh weight of young citrus seedlings (sour orange, Citrus aurantium) planted in X. brevicolle-infested soil (5 specimens/g soil) was 48% less than that of citrus grown in non-infested soil. Surveys revealed the presence of T. semipenetrans and X. brevicolle in 12 of the 13 citrus nurseries checked. This strengthened our hypothesis that these two nematode species had been brought to the plantation area along with the seedlings.
Database assignments for author(s): Mishael Mor

Research topic(s) for pests/diseases/weeds:
surveys/sampling/distribution
damage/losses/economics

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Tylenchulus semipenetrans	Citrus (genus)	Israel
	Xiphinema brevicolle	Citrus (genus)	Israel