What Is The Problem With Late Stuarts?

Everybody is talking about how late the Stuarts are on budbreak this year. UGA Horticularlist Dr. Wells was down with us this morning looking at fertilizer rates, and I asked him about this. This could be an issue if Stuarts miss pollination. Dr. Wells provides this information below:

If you have spent any time in pecan orchards in Georgia over the last couple of weeks you have noticed budbreak progressing on most varieties with one particularly notable exception. At this point Stuart is further behind most other major varieties than I have ever seen it. Why is this? Stuart has a relatively high chilling requirement—more so than many other varieties we grow. This results in later budbreak in general for Stuart. But, following a mild winter such as the one we just had (see previous post on this topic), Stuart’s late budbreak gets even later.

The biggest problem this presents is issues for pollination. Varieties that normally match up well with Stuart, like Cape Fear, Creek, Desirable, and Schley, will likely be finished shedding pollen by the time Stuart pistillate flowers are receptive. Of those, Schley may have the best chance since it is also lagging behind other varieties. If all this does translate in to poor pollination, what does that mean for the Stuart crop?

Stuart is a type II or protogynous (stigma receptivity precedes pollen shed) cultivar. Cross pollination is more important for these cultivars than for type I or protandrous (pollen shed precedes stigma receptivity) cultivars. In Type II cultivars like Stuart there tends to be complete separation of pollen shed and stigma receptivity. This helps them to avoid self pollination (which in nature results in a less fit individual). Although self-pollination is undesirable for nut production as well (it leads to increased fruit abortion and reduced percent kernel), it is better than no pollination which leads to even more fruit abortion and quality problems.

Stuarts have to make up a lot of ground quickly to avoid production problems this year.

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