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Abstract

Sunscald on trunks and branches is the most important injurious disease in old pomegranate in Yasd province, Iran. Scalded tissues become flaky and get separated from the trunk. Disorders are mainly observed on the south side of the trunks and branches. Disease symptom and lamination of bark extends to the terminal branches. In intense infection, speccially if combined with attack of borer pests such as Chrysobothris parvipunctata, leaves either fall or hang on the branches, while being either green or yellow with fruits remaining on dead branches. Roots are nevertheless normal and produce plentiful suckers in the same year and in the following years. In addition, a sudden and early low temperature in autumn aggravates the damage. No action or attempt to separate phytophthora from injuried tissues and rootzone has ended up with positive results. To study the possibility of preventing the disorder, a two year study was carried out in an old pomegranate orchard using a randomized block design or three replications. Treatments consisted of: 1- Intensive pruning in late winter, 2- As in 1, but trunks received whitewash (a mixture of white clay and barley flour) in spring, 3- Control. Results indicated that intense pruning (treatment #1) caused 65.63% scald in trunk and branches, being significantly (P—0.0 1) different from whitewash and control (treatments # 2&3). However the scalded trunk and branches in treatment #2 and 3 were 5.5 and 1.5% the difference not being significant (P—0.01). It appears that direct sunshine is the principal factor in old pomegranate trunk and branches injury in Yazd province. In case the trunks are prone to be exposed to direct sunlight, temporary white washing must be employed

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