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October 2015 P R A C T I C A L W I N E R Y & V I N E YA R D 65 S M A R T V I T I C U L T U R E We are all familiar with vineyards where individual vines are trained to a single trunk as has become the convention, but it is only a convention. In nature, and for about 40 million years, Eurasian vines have been forest dwellers; vines have been multi-trunked and unpruned, see Figure 1. It is probably in the past 5,000 years or so that vineyards have been monocultures, with each vine trained to a single trunk. Multi-trunks are a practice used com- mercially in places with severe winters to replace cold-damaged trunks, such as in New York state, and to combat crown gall that sometimes develops on cold- damaged trunks. It can be used to fight trunk diseases, too. East Coast-based viticulturist Lucie Morton suggests growers start out with two trunks to help with the inevitable development of trunk diseases, and I thor- oughly endorse this. It can also lead to earlier yields from new vines. Scientific studies in Australia since 1988 have shown that the cumulative yield losses due to Eutypa dieback can be miti- gated by taking healthy suckers from the base of the vine to replace the trunk. This technique works with other trunk diseases also. It takes advantage of saving the vine root system. Suckers arise from "base" buds at prior node positions on the vine trunk. Depending on circumstances, a proportion will burst in any growing season. These are typically seen as a nuisance by vine- yard managers, who will normally have a program to remove them, either manually, mechanically or by chemical spray. Timely trunk renewal depends on the presence of suckers and can lead to a totally new attitude to suckers if trunk diseases are present in a vineyard. The catch cry may be, "Save those little suckers!" Trunk renewal can be a "cure" for trunk disease, in that a diseased trunk and cor- dons are replaced with healthy, new parts to eliminate the infection. This helps improve yield and may slow the spread of disease by removing potential inoculum sources from a vineyard. There is, how- ever, no guarantee that re-infection will not occur, and pruning wounds must be protected by fungicide application. Growers might contemplate replacing one trunk with two, as done in the eastern United States. These new trunks can be free of trunk disease infection if located sufficiently low on the trunk, below wood cankers or discoloration due to the trunk pathogens. Australian guidelines sug- gest a 4-inch separation below staining; in New Zealand, the recommendation is 8 inches. An alternate approach that may be more suited to working with a vineyard crew is to cut at a fixed height 12 inches above ground. One grower in Cognac, Figure 1. Dr. Pierre Galet, French scientist, with a native Vitis Berlandieri vine in the Davis Mountains of Texas. Note the multi-trunks and their spread along the ground. LUCIE MORTON