>>The whole point is that oxalic treatment is not very effective until there is little or no brood and, by delaying treatment until then, the young bees that we need to overwinter will have been infested with varroa. The average lifespan of a bee with DWV is 88 days - so these bees (and therefore the colony) will not survive the winter. It is, therefore, essential to reduce varroa numbers before winter bees are reduced I agree,. I 'm told that it is most effective with little or no brood present, meaning late fall treatments. In my mind late fall treatment of severe infected colonies are a complete waste of time, money and effort. It is not the mites on the bees that kill the colony, its the mite damage to the young wintering bees that kills the colony. One step at a time, you must get the hive to early spring so they can start brooding. For a fall treatment to be effective, you have to treat at least a cycle and a half before the bees prepare for winter confinement. You must prevent the mites from entering the cell and damaging the bee. If your hives have a mite problem, your young wintering bees will already be damaged by the time you late fall treat with Oxalicacid. You will have weak stressed hives come next spring anyway and wasted effort. Ian :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and other info --- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::