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White Pine Problems, Still!

July 29, 1998

White pine problems continue throughout the state, especially in central and southern areas. Symptoms vary but generally include needle yellowing or browning, shriveled bark on branches or trunk, sap exudate on branches, and in some cases, death of the tree.

The Plant Clinic has assayed samples for pinewood nematodes; has cultured for fungal pathogens of needles, stems, and roots; and has inspected for insect infestations or injuries. The only common factor seems to be root decline. Few live white roots have been found, but fungal pathogens cannot be correlated with poor rooting. It appears that roots are on the decline for other reasons, including heat, drought, flooding, and extremes in temperature and moisture.

Many of the problem trees we have seen have been situated on clay sites or exposed to the elements (planted in new housing developments or used as windbreaks). It is likely that site stress has contributed to the decline of these trees. The excessive rains of the past several springs also may have contributed to root injury and decline by saturating the soil and causing a lack of soil oxygen.

Look for more white pine problems this year. If roots were injured as we are suggesting, they will not be able to pull up enough water to replace the loss created by the extremely hot weather of the past two weeks. Symptoms may have been masked earlier in the summer in areas where water was abundant. In drought-stressed areas, watering helps, as does the use of a natural mulch over the root system. However, without adequate root mass, plants are not able to use the available water quickly enough to replace what is used by the foliage. The result is sudden browning or off-color needles and death of branches.

Because these problems in white pine are not usually the result of an infectious disease, immediate removal of the tree is not necessary. Instead, try to keep the tree watered and see how it responds. Also, try digging into a bit of the root system for a better picture of the situation. If roots are brown in cross-section and the outer layer easily pulls off or is not present, then root injury has occurred. If the roots are white and healthy, then the problem is above ground and our theory is wrong, at least in your case.

Reports from Kentucky and other states suggest that this root decline is more of a problem in soils with very high pH levels. That certainly could be the case in many Illinois soils. Consider taking soil samples from root zones of affected and healthy trees to a soil testing lab nearby. If lab results show a very high pH level, start using the appropriate acid fertilizer to help compensate.

Author: Nancy Pataky


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