Here is an article from Dr. Lenny Wells describing shuck split on Stuart.
I’ve had a lot of calls over the last 3 weeks about Stuarts lagging behind and not opening. However, I don’t think they are actually behind as much as it seems they are. Stuart always has an interrupted and prolonged shuck split in which it opens a few and then stops, opens a few, then stops again, etc. with the result being a delay in having enough shucks split to be able to shake compared to other earlier cultivars, which have a much tighter shuck split window. This characteristic of Stuart is magnified under conditions of heavy crop load and dry soils. We tend to have short memories and this is not the first time we’ve seen this. See this blog post from 2016, in which Stuart was well into November (Nov. 10) and still not shaking well. The biggest difference in this year and 2016 is that the crop was late in general in 2016.
We do see that 2022 and 2016 have one thing in common and that is extreme drought following kernel filling. The normal maturity date (which is estimated as 50% shuck split) for Stuart is Oct. 20. So, we are a little delayed but with the extreme dry conditions we have suffered since late August/early September, this should come as no great surprise. The shuck dehiscence (shuck split) process requires water to function properly. Even with irrigation, it can be hard to supply large, old trees bearing a crop load with enough water for this process in total absence of rainfall.
We are fortunate in that though soils have been dry, the air humidity and temperatures have been relatively low. Had we had the hot, humid conditions we frequently have coupled with dry soils we would be seeing a lot of vivipary (sprouting) and embryo rot. The weather conditions have helped us avoid that problem so far.
I think the Stuart crop will open eventually, just not as quickly as we would like. Continue irrigation of Stuart orchards at about 6-8 hrs every other day or 50% of capacity to help the nuts open. I have seen some shuck decline in orchards where the irrigation has been turned off completely so the irrigation is helping. A 2″ rain would go a long way.
At this point we have seen the Pawnee harvest pretty well completed and harvest of Caddo, Creek, Oconee, Desirable, Schley, and Cape Fear well underway. So far this harvest season, we have seen a few more pops and green shucks with nothing in them than we normally see in varieties where this is uncharacteristic. This could be a result of the week or so of cloudy weather we had in August. As a result we have seen that yields from many orchards are about 1/3 off the expected weights. However, the quality of harvested nuts has been excellent for most of what I have seen to date.