Effectiveness of cyproconazole to control Armillaria root rot of apple, walnut and kiwifruit

Abstract

Armillaria root rot is a very destructive disease of apple, walnut and kiwifruit in Greece. The sensitivity of Armillaria mellea (one isolate from each of infected apple, walnut and kiwifruit) to the fungicide cyproconazole was determined by growing the fungi on Malt Extract Agar supplemented with the fungicide at concentrations of 0, 5, 10, 15, 20, 25, 30 mg/L. This fungicide completely inhibited the mycelial growth of A. mellea at concentrations of 15–20 mg/L, depending on the isolate used. The value of EC50 fluctuated between 5.189 and 6.733 mg/L for the isolates tested. In addition, experiments were conducted in commercial apple (8-yr-old; M26), walnut (6-yr-old; Juglans regia), and kiwifruit (9-yr-old; Hayward) orchards located in Macedonia, Greece. Application of treatments were made in 2009: on 10 April, 15 May and 15 September. The following year, treatments were applied only on 20 April and 30 May. Cyproconazole, applied as soil drench at a concentration of 30 mg/L (5 L/tree), showed a therapeutic activity reducing the progress of the disease in apple, walnut and kiwifruit. There was a tendency higher concentration of the fungicide (50 mg/L, 5 L/tree) to be more effective. Based on the above results, this fungicide can be possibly used to control A. mellea of apple, walnut and kiwifruit even on trees with several symptoms of the disease.