|Premature Needle Loss of Spruce|
Figure 1. Branch mortality on white spruce.
Figure 2. Browning needles of black spruce.
|Premature needle loss on white, black and Norway
spruce has been observed in forest plantations in Wisconsin and Minnesota
during the past six years. Symptoms vary by species but usually appear first in
2-4-year old needles on lower branches. Infected needles are dropped, resulting
in branch mortality that progresses upward through the crown, sometimes killing
even large, dominant trees. Several insects and fungi, as well as abiotic
stresses such as drought and poor soils, appear to contribute to the damage.
The fungus Rhizosphaera kalkhoffii is the only organism that has, been
consistently associated with needle loss. R. kalkhoffii is commonly
found on ornamental blue spruce throughout Minnesota and Wisconsin.
Figure 3.Discoloration of older needles of Norway spruce.
|Watch for: Needles turning prematurely yellow and
finally brown; small black fruiting bodies of R. kalkhoffii, which
emerge in rows through the stomata; excessive lower branch mortality; and thin
Forest Service plant pathologists are examining this disease and evaluating possible control measures. You can help us to delineate the extent of the problem by reporting any suspected occurrences of this syndrome on spruce other than Colorado blue spruce, which is habitually infected.
To report infected stands or to receive further information, please contact:
Figure 4. Fruiting bodies on attached needle of Norway spruce.
|Jennifer Juzwik, Forest Insect and Disease Research,
Joseph G. O'Brien, Forest Pest Management, State and Private Forestry
USDA Forest Service
1992 Folwell Avenue
St. Paul, MN 55108