Evaluation and estimation of the population of citrus root nematode and Phytophthora in healthy and citrus decline infected trees in southern Iran

The citrus industry contributes significantly to the agricultural productivity and to Iran’s economy.
Recently, occurrence of citrus decline disease (CDD) has caused severe threat in citrus orchards in the southern part of Iran.
The disease symptoms start with significant growth retardation of infected plants leading to visible weak appearance of trees.
Severe root rot is common in infected trees.
In this research work the distribution of CDD, the population of citrus root nematode (Tylenchulus semipenetrans) and Phytophthora spp. were counted in both healthy and infected trees.
The partial distribution of CDD is estimated to be around 76%. The results showed that investigated samples were infected with citrus root nematode from moderate to severe level.
Mean number of female nematode population per gram of infected and healthy root was reported 210 and 11, respectively.
The mean of 2^nd larva populations 200 cm^‑3 soil samples of infected and healthy plants was calculated 2573 and 183, respectively.
The numbers of propagules of Phytophthora in per gram of soil of infected and healthy trees were reported 13.5 and 4, respectively.
Inoculations of ‘Bakraee’ seedling (rootstock) with nematode and Phytophthora showed severe root rot and nematode infection and finally death of plants.
Based on our research results a complex of Phytophthora and citrus nematode are associated with CDD and can affect the disease severity in the south of Kerman, Iran.

XV International Citrus Congress

M. Najafiniya, M. Azadvar

root rot, sudden decline, Jiroft, nematode and fungus

https://doi.org/10.17660/ActaHortic.2026.1448.75