Question: Should I re-apply grow tubes in the spring of the second year (before second leaf) in order to get another season of herbicide protection?

Answer: It is highly recommend that you remove grow tubes in autumn. Because vines in grow tubes are under far less stress, the period of active growth extends farther into the late summer and early fall. This can leave the vines more vulnerable to frost damage. This can be completely prevented by removing the grow tubes in early to mid-September.

If your extension agent or viticultural expert recommends re-applying grow tubes the following spring, follow this recommendation. The grow tubes will have little to no further beneficial effect on growth (having increased balanced biomass growth by 70% or so in first leaf), but they will continue to provide protection from herbicide spray, dramatically reducing the man-hours required to maintain the vineyard.