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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 67 S M A R T V I T I C U L T U R E managers may be concerned with such a departure from con- vention. Removal of the old trunk can be an issue. Especially if spur- pruned, the fruiting wires may be ingrown in the wood, and often trunks, cordons and wires need be removed, and trunks destroyed. The broad aim of the TTR protocol is to reduce the impact of grapevine trunk disease on vineyard profitability. The protocol aims to: 1) Retain health and recover yields to profitable levels, before yield losses are too severe. 2) Manage the disease to conserve production where possible, in vineyards at an early to moderate stage of infection, or those with a higher risk of infection. 3) Minimize costs and maximize revenue in all instances. General assumptions 1) The protocol defined below is not applicable to vines with unhealthy root systems, which may be caused by root patho- gens or for other reasons, or to vines with other diseases such as virus. 2) The cordons and, to a lesser extent, the trunks of mature vines are likely to have more wood cankers and discolor- ation than those of young vines. The greater the proportion of such wood symptoms, the greater is the impact on yield. 3) Present abiotic stresses may compound damage from trunk disease. Sometimes the stress should be addressed before trunk renewal, as for example with poor soil drainage. 4) Use of healthy suckers arising from base buds well below wood symptoms offers the opportunity for trunk renewal while retaining the original root system. Vineyard procedures for the protocol Normally a vineyard is made up of discrete blocks, which may differ in grape variety, clone, rootstock and date of planting etc. The following protocol is designed to be applied at the block level. 1. Trunk disease infection assessment: Each block needs to be assessed for trunk disease, and this assessment can be at vari- ous degrees of accuracy, from visual ratings of numbers of dead spurs per vine, for example, to counts of vines with the presence of canopy symptoms. Dead, missing vines, replants and other- wise symptomatic vines need to be recorded also. Timing of inspection depends on the predominant trunk dis- eases in the vineyard. Foliar symptoms of Eutypa are most appar- ent in spring. Symptoms of Esca do not start to develop until approximately mid-June. Dead spurs and stunted shoots are best observed later in the growing season, when vegetative growth ceases. 2. Trunk disease risk assessment: All vineyards in California are attacked by one or more trunk diseases, eventually. Obviously the older the vineyard, typically the greater the level of damage. The time it takes for canopy symptoms to first appear, the rate at which the proportion of symptomatic vines increases and the severity of yield losses are all influenced significantly by grape variety. The varieties Sauvignon Blanc and Ugni Blanc are among the most susceptible to Esca. Merlot seems to be more resistant to Eutypa dieback than Cabernet Sauvignon, although they are both similarly susceptible to Botryosphaeria dieback. In California, seed- less table grapes (namely Thompson seedless) are very suscep- tible to Phomopsis dieback. It is not possible to present a general table of trunk disease susceptibility, since experience suggests that this may vary from region to region, maybe vineyard to vineyard. The best approach