Littleleaf Disease
Forest Health Guide for Georgia Foresters
Written by Terry Price, Georgia Forestry Commission
Adapted for the web by the Bugwood Network
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Around 1936 trees having yellow-green foliage and unusually short needles characterized many of the shortleaf pine stands that had seeded in on abandoned farmlands in the Piedmont regions of Georgia. The trees were best described as having littleleaf symptoms; hence the name littleleaf disease. Many of the stands were 20 to 30 years old. Further investigations associated the syndrome with soil series such as Wilkes, Mecklenburg, Tatum, Orange, and Vance. The sites were severely eroded due to previous agricultural activities and subsequent abandonment. The topsoil was almost completely eroded away. On such sites, tree roots were weakened by heavy clay subsoil with poor internal drainage.
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Research then and more recently has identified at least two soil-borne fungi associated with littleleaf; Phytophthora cinnamomi, and species of Pythium. These fungi kill the root tips of stressed trees. As more and more feeder roots are killed, essential element uptake by the tree is reduced even though adequate elements may be present. As trees weaken the symptoms become more pronounced (Figure 119). Trees eventually die from littleleaf.
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Figure 119
photo from USDA Forest Service Archives |
The disease is most prevalent in stands 30-50 years old. The fungi associated with littleleaf are widely distributed in the soils of the southeastern United States.
There is no cure for littleleaf disease but there are several recommendations that foresters can follow to minimize losses. Trees under 20 years of age or 3-4 inches in diameter rarely show littleleaf symptoms. Infected trees can live as long as 5 to 6 years after initial symptoms appear but some trees may die in as little as one year. This is particularly true during extended droughts or when bark beetles have attacked trees.
The amount of littleleaf in a stand dictates the management of that stand. The following guidelines should help foresters and landowners better manage their littleleaf stands:
- If up to 10 percent of the trees in the stand have symptoms, all diseased trees should be removed by ten-year intervals.
- If 10-25 % of the trees in the stand have symptoms, remove all diseased trees at six-year intervals.
- If 25-50% of the trees in the stand have symptoms, clearcut and regenerate with Virginia pine or hard woods. This is particularly true for stands being managed for pulpwood. Loblolly pine is about one- third as susceptible as shortleaf and may be considered as an option on littleleaf sites. It does, however, sustain severe damage on many sites within the range of littleleaf disease. Rotations for loblolly on high hazard sites should be shortened to 30 or 40 years.
- Soil amendments with a 5-10-5 commercial fertilizer and ammonium sulfate can prevent symptoms from developing and will benefit trees in the early stage of the disease but are only practical for speci- men or historic trees.
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