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A microscopic arachnid is attacking many local trees and plants.
Damage from infestations of the eriophyid mite complex has been seen on Arizona ash, along with desert willow, mesquite, purple-leaf plum, sycamore, vitex and Chinese Pistache trees, said Doña Ana County Cooperative Extension Service Agronomy and Horticulture Agent Jeff Anderson. Bushes suffering damage include creosote, oleander, lantana and desert bird of paradise, he said.
Worse, “the host range seems to be expanding,” Anderson said.
Toxin from mites causes changes to hormones within the buds of trees and plants being attacked so that they do not signal correctly for the plant to grow, Anderson said. The result is that the tree or plant does not leaf out, or new growth is very distorted, creating a witches’ broom effect or a mass of nubbin-like small bumps where the leaves should be coming out. If trees and plants do not leaf out properly, they could die, he said.
Because mites are arachnids (the same class as spiders) not insects, insecticides won’t kill them, Anderson said. “You have to use an arachnicide,” he said.
Anderson has recommended using treatments of liquid sulfur to spray branches and buds, rotating with the miticide Avid. Other miticides may also be effective, Anderson said, but they produce strong odors. He does not recommend cutting off branches of infected trees and plants
“That’s the last resort,” Anderson said.
Anyone who thinks they may have mite damage, especially if any is noticed on pecan trees, is asked to send detailed photographs of the damaged tree or plant, along with a phone number, to Anderson at firstname.lastname@example.org.
“I can take a look at it, call you and we can discuss it,” he said.
Anderson said there is no known cause for the infestation. Mites cannot fly, so they are likely spread by the wind or on bird feathers, he said.
If an herbicide has been used nearby, damage to trees and plants can mimic mite damage, Anderson said, and there could be other causes as well.
“A careful analysis of each situation is important to make a correct diagnosis and treatment recommendations,” he said.