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Nursery & Forest
Volume 56 Number 13 Date 07/21/2011 GYPSY MOTH - The final mating disruption treatment was applied in the Superior area of Douglas County on July 19, marking the end of the annual gypsy moth spraying season. Treatment began on May 23 and was delayed in many instances by rain and strong winds. More than 250,000 acres in 22 counties were treated by DATCP's Slow the Spread Program this year. --Nkauj Vang, DATCP Nursery Inspector Program TUBAKIA LEAF SPOT - This common, late-season fungal disease was diagnosed on red oak from a Marquette County nursery. The symptoms are well described by the name "leaf spot" and include dark brown or reddish-brown spots or blotches on the foliage. Spots that occur on leaf veins may develop into large, extensive areas of dead leaf tissue. Premature defoliation is common in heavily infected trees. Due to the late onset of symptoms, fungicide sprays are not recommended. Maintaining tree health by adequate watering and fertilization will usually reduce occurrence of this disease. VENTURIA SHOOT BLIGHT - Quaking aspens at a nursery in Jefferson County are showing the black, blighted shoots indicative of this fungal disorder. The initial symptoms appear in May as irregular brown or black spots on the leaf surfaces, which later expand to new shoots and cause a characteristic shepherd's crook. Secondary infection cycles can occur throughout the shoot elongation period, particularly during prolonged wet periods. The fungus overwinters in infected shoots, so pruning blighted shoots below the margin between healthy and diseased tissue is recommended. -- Liz Meils, DATCP Nursery Inspector COOLEY SPRUCE GALL ADELGID - Nursery inspectors report that the pine cone-shaped galls of this insect are forming on Serbian spruce trees a in Chippewa County nursery. The Cooley spruce gall adelgid has a complex, two-year lifecycle in which it transitions into five different morphological forms and moves between firs and spruce. The galls are visible from early to late summer in Wisconsin. Horticultural oil sprays should be applied in the spring before new growth starts or in the fall when overwintering stages of the insect have returned to the tree. Treatment is ineffective once the galls have formed. Adequate spacing of Douglas firs and Colorado blue spruce trees may help to limit movement between the two conifer hosts. WHTIE PINE BLISTER RUST - Yellow currant shrubs at a nursery retailer in Clark County were moderately infected with white pine blister rust. This two-host fungal disease spreads from currants (Ribes spp.) to eastern white pine from mid-July through late fall, and requires both plants to complete its life cycle. Symptoms on infected currants are the orange spores produced on the undersides of leaves. Moderate to high densities of both host plants in the same general area can result in severe infection and mortality of white pines. -- Konnie Jerabek, DATCP Nursery Inspector 
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