Publishing Date: 2005

E-ISSN: 0255-7576

Volume 23 Issue 2


Seasonal fluctuations of the citrus nematode were studied over twelve months, in a 7 year-old orchard of ‘Washington navel’ on sour orange (Citrus aurantium) rootstock in the Central Jordan Valley. Tylenchulus semipenetrans population densities peaked in November and March, while declined to lower levels in January and August. Numbers of second stage juveniles (J2) in soil and developmental stages in roots (eggs, J2 and females) recorded in each month were significantly and positively correlated with root biomass (r = 0.52 to 0.75) and the starch content in fibrous roots (r = 0.65 to 0.72). Favorable soil temperature between 22 to 27° C prevailed when citrus nematodes were most abundant. The November peak occurred during a period of moderately suboptimal soil temperature (average 22.3° C), highest root biomass (4.7 mg/cm3 soil) and low starch content. Subsequently, nematode number declined due to lower temperature and low amount of biomass and starch. The March peak coincided with suboptimal soil temperature (average 22° C), high biomass (4.2 mg / cm3 soil), and high starch concentration (6 %). A decline in nematode numbers during April and May coincided with lower root starch content and root biomass, although temperature was optimal (25-27° C). The minimum population densities in January and August corresponded to very low (average 15° C) or very high (average 34° C) soil temperatures, res pectively