HarborTown,
You are opening a whole can of caterpillers with the use of Timbor on actively growing hop plants. Low relative mammalian toxicity, yes. Labelled for use around plants, no. Effective as a wood preservative, yes. The same active ingredient used as a "common" micro-nutrient fertilizer, no, not really. Boron an important element in plant growth, yes. Very narrow (parts per million) range between boron benefits and boron toxicity to the plant, YES. If you must treat the wood, I'd suggest waiting until this fall, when the hops go dormant. In the meantime, I'd get a soil test to determine your soil nutrient levels and then contact the local county Ag. extension agency to get their recommendations on wood treatments and soil/plant toxicity in your area. Just like pH in mashing, soil pH plays a critical role in plant health.
