Effectiveness of selected fungicides applied with or without surfactant in controlling anthracnose on three cultivars of Euonymus fortunei.

Abstract

The effectiveness of six fungicides applied with and without the surfactant Hyper-Active™ in controlling anthracnose caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. on three cultivars of Euonymus fortunei (Turcz.) Hand.-Mazz. was evaluated at two locations, Stillwater, OK and Fayetteville, AR. The fungicides tested were mancozeb, copper hydroxide, trifloxystrobin, chlorothalonil, myclobutanil, and azoxystrobin. These fungicides were also incorporated into potato dextrose agar (PDA) to determine the effective concentration to obtain 50% inhibition (EC 50 ) of mycelial growth of C. gloeosporioides. In the field, chlorothalonil and mancozeb were the most efficacious of the fungicides tested. Presence or absence of the surfactant Hyper-Active™ in fungicide spray solutions did not affect control of anthracnose symptoms. Cultivars varied in susceptibility to anthracnose. At Fayetteville less anthracnose symptoms appeared on ‘Emerald Gaiety’ and ‘Emerald Surprise’ than on ‘Emerald ’n Gold’; however, at Stillwater, disease incidence was similar on ‘Emerald ’n Gold’ and ‘Emerald Surprise’. Mycelial growth in culture was most inhibited by the fungicides myclobutanil and trifloxystrobin.