Influence of irrigation and fungicide sprays on prevalence of Erynianeoaphidis (Entomophthorales : Entomophthoraceae) infections of greenpeach aphid (Homoptera : Aphididae) on spinach

摘要

Infections from Erynia neoaphidis (Remaudiere & Hennebert) have often resulted in epizootics in green peach aphid, Myzus persicae (Sulzer), populations on spinach, Spinacia oleracea L., produced for processing in the Arkansas River Valley of Arkansas and Oklahoma. Use of this fungal pathogen as an aphid management tool has been unsuccessful because of poor timing, i.e., epizootic occurrence generally occurs at or after harvest. In the study reported herein, attempts at manipulating disease occurrence with overhead irrigation and fungicide applications were made. In samples 16- to 35-d after irrigation was initiated, the percentage of aphids infected with E. neoaphidis was significantly greater than in aphids from plots not receiving irrigation. The percentage of infection in the 35 d sample was twice as great in irrigated plots as in those not irrigated. In subsequent samples, however, significant differences were not detected and peak epizootic did not differ between the irrigation treatments. M. persicae populations were eliminated in both blocks 63 d after sampling was initiated. The fungicide, manganese ethylenebisdithiocarbamate, initially had little detectable effect on disease prevalence; however, in samples taken 21- and 41- d after the initial application, percentage of aphids infected with E. neoaphidis was significantly reduced.