The influence of systemic inducing agents on horse chestnut leaf miner (Cameraria ohridella) severity in white flowering horse chestnut (Aesculus hoppicastanum L.)

Two separate trials during 2010 and 2011 were conducted using field grown white flowering horse chestnut trees (Aesculus hippocastanum L.) to asssess the insecticidal efficacy of three systemic inducing agents (SIR), namely (Messanger (active substance (a.s.) Harpin protein), Phoenix (a.s. Potassium phosphite) and Rigel (a.s. Salicylic acid derivative) applied to coincide with the appearance of each adult generation of the insect pest, horse chestnut leaf miner (Cameraria ohridella Deschka and Dimic; HCLM). A conventional synthetic insecticide (deltamethrin) used within the UK for HCLM control was included for comparison. A marked impact of SIR inducing agent and frequency of application on HCLM severity was recorded. The effectiveness of each SIR inducing agent on mean number of HCLM mines per leaf and percent HCLM larvae/pupae mortality increased when applied at increasing frequencies i.e. three sprays provided greater control than two sprays while two sprays provided greater control than one spray. The synthetic insecticide deltamethrin provided the greatest degree of HCLM control with two foliar sprays providing 100% HCLM control. Efficacy of SIR inducing agents based on reduction of HCLM mines per leaf after three sprays averaged across both the 2010 and 2011 growing seasons was in the order potassium phosphite > salicylic acid derivative > harpin protein > water control where leaf mining activity was reduced by 35–64%. Enhancement of leaf phenolic content was indicated as a means by which SIR agents reduced leaf mining activity. Results show commercially available SIR inducing agents exist that provide potentially acceptable degrees of HCLM control provided at least two sprays are applied during a growing season.     

Sooty canker,a destructive disease of banyan (Ficus benghalensis L.) trees in landscapes of Kish Island (Iran)

Ficus benghalensis L (banyan tree) has been planted as ornamental tree in parks, landscapes as well as along roads and streets in many southern cities of Iran. During field surveys conducted in Kish Island (Hormozgān province) an unusual decline was noticed on F. benghalensis. Affected trees exhibited bark necrosis, peeled off bark and cankers on branches and aerial roots, yellowing and defoliation, branch dieback and eventually death. A black sooty mass of fungal spores under the bark as well as wood discoloration in cross sections were also observed on infected parts of trees and pruning wood debris. Samples were collected from all affected parts of trees showing disease symptoms, pruning wood debris as well as rove arthropods in close proximity to the trees for the presence of fungal inoculum. In this study 239 Botryosphaeriaceae-like isolates were obtained from discoloured wood tissues, pruning wood debris and from the bodies of collected arthropods. Based on morphological characteristics and DNA sequence data of ITS and tef-1α gene regions, isolates were identified as Lasiodiplodia theobromae and Neoscytalidium dimidiatum. Pathogenicity of both species was performed on the branches of banyan trees and L. theobromae was more virulent, based on the length of necrotic lesions in the wood, than those of N. dimidiatum. This study is the first report of N. dimidiatum associated with sooty canker and dieback of F. benghalensis worldwide. Our study showed for the first time that L. theobromae and N. dimidiatum can also be associated with some arthropods. Our outcomes can improve the management strategies of trunk diseases caused by Botryosphaeriaceae species on ornamental trees in landscapes.