Control of Eutypa Dieback of Grapes
The objective of our research is to find an effective control for Eutypa dieback, caused by the fungus Eutypa lata. This disease is difficult to study, because several years can elapse between the time of infection and the appearance of symptoms. Specific objectives this year were to continue testing efficacy of the fungicides Benlate 50 WP (multiple applications). Rally 40 WP, and Nustar 20 DF, to study colonization of wounds by applied fungi, to determine how the biological control agents inhibit infection by Eutypa, to test the combination of Benlate and Fusarium applied together, and to monitor the natural flora of pruning wounds of grapevines. The fungicide experiments are still in progress, but data obtained thus far indicate that applications of benlate at 1 and 14 days after pruning is more effective than only one application at pruning. The second application appears to protect the wound during the later half of the wound healing process which ultimately protects the plant from infection. Thus far, none of the inoculated vines that recieved two applications of benomyl have become infected with Eutypa. The biological control agents are spore suspensions of the fungi Fusarium, Clado.sporium, Aureobasidium, Trichoderma, and PeniciIlium. Our studies have shown that these fungi can successfully colonize the wound surface when we apply them as spore suspensions. These fungi also are effective in reducing infection by Eutypa, but those studies must be conducted over many years to observe results over a variety of weather conditions Studies on the natural wound colonization showed that numbers of filamentous fungi, yeasts, and bacteria are initially zero, and increase rapidly for 7-14 days after pruning, then remain constant.