Symptoms of pests, rust and other disorders on leaves of willow fertilised with wastewater, urine or sewage sludge

Willow (Salix viminalis) irrigated with three different dosages of wastewater has been investigated for leaf damages in four plantations located in Sweden, Northern Ireland, France and Greece, during 3 consecutive years. Control treatments were clean water and/or no water. Additionally, the plantation in Sweden included a human urine/water mix treatment and the one in N. Ireland a sewage sludge treatment. Few effects of the treatments were found. In the Greek trial, all treatments were affected by abiotic stress causing leaf discolouration, necrosis and leaf curling, but the control treatment was least affected. Mite, infestations were also less prevalent in the control plots there. In the French trial, control leaves were less galled by Dasineura marginemtorquens than leaves from the lowest dose of wastewater but not compared to the two higher doses of wastewater, during I of the 3 years. At the same site, but in another year, Melampsora rust infection was least developed at the highest dose of wastewater but only significantly so when compared to the intermediate dose of wastewater. Urine/water treatment resulted in more rust and leaf margin damages than the control treatments in 1 year. Also, leaf spotting by leafhoppers tended to be more prevalent on the urine treatment. However, since the urine fertilisation favours willow growth as well, a somewhat enhanced biotic damage to leaves is probably no reason for avoiding this application in full-scale plantations. Damage by chrysomelid beetles was very common in the French and the N. Irish plantations, but no significant differences between treatments were found. Neither were there any treatment effects on symptoms by aphids. (C) 2008 Elsevier Ltd. All rights reserved.