Native Species Attack on Trees Not Fatal

South Lake Tahoe, Calif. —On Pioneer Trail near the intersection with U.S. Highway 50 in Meyers, some Jeffrey pine trees appear to be dying.  In fact, the yellowing of the needles is due to the work of a native insect species known as a “needleminer” that feeds on the needles of pine trees.  While this particular needleminer feeds only on Jeffrey pines, it is closely related to others that live in Lodgepole and Ponderosa pines.

Jeffrey Pine needleminers eat their way through the middle of the needle, causing the needle to die and turn yellow or, in extreme cases, red.  Trees can appear to have red halos because the needleminer primarily targets the tips of the needles.  Only when all the needles on an infested tree turn red does it mean the tree has died.  Although the trees look as though they are severely damaged, more often than not they will recover once there is a reduction in the needleminer population.  Fortunately, there is a natural biocontrol agent that regulates the needleminer population, meaning it keeps the needleminers in check.

Jeffrey pines are more susceptible to needleminers when they are under severe drought stress.  Once trees are infested by needleminers, they can lose strength and attract other harmful pests, such as bark beetles.  With record-setting drought conditions in California and Nevada, it is more important than ever for communities to do their part to conserve water, thin dense tree stands, and improve growing conditions (i.e. tree vigor) to help trees become resilient to potential infestation.

While the infestation appears to be contained to small segments of Pioneer Trail, it is possible for the needleminers to spread to other parts of the basin.  Forest Service personnel are monitoring the situation, and the extent of the outbreak will be determined later this summer during an annual aerial survey flight.

For more information, contact the Lake Tahoe Basin Management Unit Forest Supervisor’s office at (530) 543-2694.

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