My Pine Tree Needles Are Wilting

Pine Wilt

• Pine wilt is an extremely lethal disease that affects most species of pine and is capable of killing the tree in a matter of weeks or months. The disease turns needles gray, then tan, and finally, brown, with the dead needles remaining on the tree for as long as one year. Depending on the circumstances, only scattered branches may initially be affected; in other cases, the entire tree displays symptoms of the problem simultaneously.

Varieties Most Affected

• Scots pine is especially susceptible to pine wilt. Other pine species like Red, Jack and Austrian pines are moderately susceptible to the infection, while the disease rarely attacks White pine. Older pines are especially at risk, with nearly all cases of pine wilt occurring in trees more than a decade old. The disease is so damaging to trees in the Midwest that extension authorities in several states recommend gardeners avoid planting susceptible pine species. Pine wilt also ravages pine forests in China and Japan.

Disease Development

• The pinewood nematode (Bursaphelenchus xylophilus) and the pine sawyer beetle (Monochamus) are the two insects involved in the development of wine wilt. The nematodes live within the pine sawyer beetles, with the nematodes moving into the pine tree as the beetle feeds. In turn, the feeding of the pine nematodes disrupts the flow of resin and water through the tree. Deprived of hydration, the needles of the pine begin the process of browning and wilting.

Management

• Once a tree has contracted pine wilt, there is nothing that can be done to save it. The problem is exacerbated during periods of high summer heat, a condition that allows the pine nematodes to thrive. Water stress during drought also contributes to the problem. Insecticides are ineffective against pine wilt disease, with the best management practices focusing on sanitation and reducing the spread of the disease. Dead or dying pines should be promptly removed and destroyed.