Experts: More than 60 acres of macadamia trees affected by lava

PUNA, BIG ISLAND (HawaiiNewsNow) - More than 60 acres of macadamia trees in Puna have been overrun by lava or, by being in the evacuation zone, are vulnerable to theft by humans and wild pigs.

Hawaii macadamia nut growers, convening over the weekend in Hilo, shared reports on damage, estimating 32 acres were known to be overrun by lava plus 34 acres isolated by lava – in a kipuka.

Growers at the Hawaii Macadamia Nut Association, Saturday at Nani Mau Gardens, said there was little impact so far in other parts of the Big Island.

Kipuka acreage in Puna is beset by thieves who have made off with generators, four-wheelers, welders and other valuable equipment.

Thieves get in through gates left open for livestock to flee lava, which is now entering some kipuka areas. Feral pigs, puaa, also get in, and they are eating the macnuts.

Puna farmers said thieves and pigs alike are getting in and out through Isaac Hale Beach Park but it appears also to be happening in other places.

The threat isn't entirely from lava, thieves and pigs. Sulfuric fumes are also potentially harmful to macnut trees, but only under certain conditions.

"Plants generally do not display symptoms of SO2 injury until the standards affecting human health are met or exceeded," said Eli Isele, UH assistant extension agent for sustainable agriculture.

"Sulfur dioxide must enter leaf mesophyll tissue, through stomata, to cause plant injury. If the stomata are not open, due perhaps to water stress or other causes, plants may escape severe injury. However, once SO2 enters the moist mesophyll tissue, it combines with water and is converted to sulfuric acid which burns plant tissue – from the inside out."

Farms further away in Kau and Puna have shown some damage from young tissue in the fields and nurseries, but plants are not showing long term damage, Isele told the conference.

That's the good news. The bad news is that continued downwind SO2 exposure through next March could lead to serious damage to their flowers.

"The flower is very sensitive to SO2 and this could significantly affect their 2019 to 2020 yields," Isele said.

Macnuts grown in Keaau and Hamakua appear safe from sulfuric fumes so far, and the same seems true so far for the massive MacFarm operation west of Kau. For those unaffected it could be a very good year, because farmgate macadamia nut prices have never been higher.

UH Manoa is offering free soil testing and water testing in the affected areas of Puna and Kau.

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