Heerema sees scattered cases of mouse ear in orchards in New Mexico’s Mesilla Valley. The nutrient deficiency is more commonly found in eastern New Mexico and Texas.

As with many other micronutrients, he notes that soil samples will not provide an accurate picture of nickel availability for tree uptake.

“With all metal nutrients - ­zinc, copper, iron, manganese, and nickel­ - they become unavailable in high pH soils and calcareous soils in the southwestern U.S.,” Heerema said.

Although lab results from leaf samples may provide information about deficiencies of several nutrients, the usefulness of nickel data is still viewed as questionable.

“We don’t have a very good interpretation of leaf analysis (for nickel),”" Walworth said. “We haven't pinned down the acceptable levels yet.”

For growers who pull samples for laboratory analysis, Heerema says first rinse leaves in a phosphate-free detergent, such as dish soap.

If foliar nutrients were applied before sampling, Heerema recommends running the leaves through a 0.1 percent hydrochloric or muriatic acid solution. Since acid is caustic, he urges growers to wear protective gloves and safety glasses.

Next, the leaves should be rinsed three times in deionized or distilled water, available at many discount stores.

“Cleaning the leaf is very important,” Heerema said.

Nickel levels higher than 2.5 parts per million are considered adequate, according to the NMSU Extension publication, “Diagnosing Nutrient Disorders of New Mexico Pecan Trees.”

In orchards with mild mouse ear symptoms, Heerema says a single foliar nickel application early in the season is typically enough. He has worked with nickel lignosulfonate, and a handful of other nickel sulfate products available on the market.

The nickel lignosulfonate label says the product can be successfully tank mixed with other nutrients or crop protection materials. Yet Heerema has heard from several growers who suggest that applying nickel separately from other materials brings better results.

In severe mouse earring cases, Heerema says growers can apply another foliar nickel treatment about one to two months after the first - timing it to impact the midseason flush. A third treatment, if needed, can be applied in the fall.

The pecan specialist said, “In many cases, a single application in the spring is sufficient.”

With nickel, a late-(season) application can carry over. The demand for nickel is so low and it's required in such small quantities that the amount that can move around and into storage sufficiently to help.