Effects of soil solarization and some amendments to control verticillium wilt in established olive orchards
The effects of solarization treatments, alone or with organic amendments and urea against verticillium wilt on olives were studied. Trials were carried out during the 2005 - 2007 seasons in an olive orchard consisting of 700 4 - 6 year old trees (cv Gemlik) in Germencik region of Aydin. Five treatments were carried out: Solarization (S), solarization + chicken manure (SCM) (1 kg m-2), solarization + olive processing waste (SOPW) (2 kg m-2), solarization + urea (SU) (100 g m-2) and an untreated control (C). Maximum soil temperatures reached in solarized plots were 54.7 and 43.9°C and in the non-solarized plots were 44.4 and 37.4°C at 5 and 20 cm soil depth, respectively. At the end of two years, the disease incidence and severity index decreased to zero in the treatments that included S. In the SCM treatment and in the control, the highest severity index (8.0) was recorded while the disease incidence slightly decreased from 66.7 to 44.4%. In SOPW plots, the disease severity index decreased to 2.0 and the disease incidence remained the same. In SU plots, the disease severity index decreased from 5.6 to 4.5 and disease incidence slightly decreased to 44.4%. As a result, the trees treated with solarization alone and solarization with olive processing waste showed an increased recovery and symptom remission compared with the initial disease severity and incidence.
Key words: Olea europaea, Verticillium dahliae, amendments.