“One is always looking to be more authoritative than the other,” Professor Heilman said, “and one of the ways they’re making this happen is over matzo — our matzo is more kosher than yours, we’re more scrupulous and careful over matzo baking than you are.”

Zalman Teitelbaum is the younger of the brothers and a rabbi in one of the Satmar congregations in Williamsburg, where many of the sect’s members live. The bakers who follow him use East Coast wheat.

Image A Christian farmer's wheat in Yuma, Ariz., becomes matzo.

Aaron Teitelbaum, the older brother, is the chief rabbi of the Satmar community based in the village of Kiryas Joel, N.Y., settled by his great-uncle, Joel Teitelbaum, the dynasty’s founder and its grand rabbi. Wheat used there comes from Yuma.

On Monday, Rabbi Aaron Teitelbaum got something close to a rock star reception when he paid a visit to the farm, straight from New York, to bless the wheat harvest. Rabbis and congregants at the farm formed a tight knot around him, taking pictures and jostling for a chance to touch him.

Rabbi Brody, clad in a bekishe, a traditional ankle-length black coat, approached Tim Dunn, the farm’s owner. “How many degrees is now?” he asked.