It’s a wrenching sight, walking into your pomegranate orchard and seeing crippled or dead trees.

To varying degrees, that happened this year to at least three growers who were among those who gathered for a pomegranate field day in Parlier and Reedley where researchers solicited anecdotal information on the mystery of just what is harming the trees.

The three growers — David Lometti, who farms in the San Joaquin area; Gary Davis, who manages a farm in the Firebaugh area; and Mike Brenner, who welcomed workshop participants to his orchard in Reedley — blame cold temperatures in part.

They have agreement from Themis Michailides, a University of California plant pathologist, who said many questions remain, but “low temperatures have a lot to do with this problem.”

Michailides cited a research paper from Iran that showed similar cold snap damage in 1998.

He said still more research needs to be done on what is being called “tree decline,” a problem that dates back at least four years in the Central Valley, where acreage has grown to 33,500 acres.

None of the three growers is about to walk away from the problem. Davis, for example, said the loss of 10 percent of the trees in one orchard has not dampened enthusiasm for new plantings. With 220 acres in production, the farm he manages, J&J Farms, planted 53 more acres this year and may soon add more than 100 more.

But the loss of trees is an obvious source of frustration and puzzlement.

Lometti wondered if nematodes could be part of the problem. Researchers say nematodes, like the cold temperatures, could perhaps open the door to decline.

Brenner’s losses totaled 30 percent to 40 percent “on average,” he said.

He and others say younger trees — his damaged Wonderful trees are about four years old — are more vulnerable than older plantings. Brenner said that suckers that emerged around trees did not fare well, becoming brittle.

Davis had more luck, he said, because his is a trellised orchard of high density, and he was able to tie new growth to the trellis. He said an Israeli variety was unscathed.

Michailides said one of the mysteries concerning the dieback is the fact that some trees remain healthy while others die, and they may be side-by-side.