According to the weekly Mercaz HaInyanim, the famous esrog tree of HaRav Michel Yehuda Lefkowitz zt"l, that grows in the courtyard of his modest house in Bnei Brak, has stopped giving fruit this year after the passing of its owner, one of the gedolim of the generation.
The tree had been giving fruit for more than seventy years, after the Chazon Ish gave HaRav Lefkowitz several seeds from the esrog that he had used. HaRav Lefkowitz had visited the Chazon Ish right after Succos, and after they spoke in learning the Chazon Ish gave HaRav Michel Yehuda an envelope containing several seeds from the esrog he had used that year. The Chazon Ish asked HaRav Michel Yehuda to plant the seeds in the yard of his home so that fruit descended from this esrog, which the Chazon Ish had determined to be a pure esrog without any admixture, would be available in the future. In fact, the tree planted by HaRav Michel Yehuda served as the basis for the thousands of esrogim sold every year as being from the Chazon Ish strain of esrogim (sometimes also called "Lefkowitz strain").
When HaRav Michel Yehuda tried to decline the offer of the seeds, saying that he knew nothing about raising esrogim and that he was worried that it might take a lot of his time, the Chazon Ish said, "HaKodosh Boruch Hu can send brochoh with one gust of wind."
Despite the fact that HaRav Michel Yehuda knew very little about growing esrogim and that he spent very little time taking care of the trees, they soon produced nice and bountiful fruit. The Chazon Ish later used their fruit on Succos, and throughout the years many talmidim of the Chazon Ish used the esrogim as well as great and famous rabbonim and admorim.
Even this year, many came to make the bircas ilonos on the flowers of those trees in Nisan this year. However after HaRav Michel Yehuda was niftar on 23 Sivan, the trees started to lose their flowers and even their leaves. Any fruit that had started to grow fell off.
According to Yisrael Cohen writing in Mercaz HaInyanim, the Admor of Toldos Aharon, who had used HaRav Lefkowitz's esrogim for many years, sent a number of experts to examine the trees. They could find nothing that explained the behavior of the trees, all of which seemed to be in good health.