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Nursery & Forest
Volume 58 Number 2 Date 05/09/2013 COOLEY SPRUCE GALL ADELGID - Overwintered immature females are active and should be noticeable on the undersides of Colorado blue spruce branches near the base of new swelling buds. The females develop rapidly in early spring, producing eggs that soon hatch into nymphs. Their feeding stimulates new shoots to elongate into the pinecone-shaped galls that encompass the entire shoot. Control must occur before the females develop their white waxy coverings. The preferred treatment window is in early spring before new growth starts. The next treatment opportunity will be in fall after the last generation of nymphs has settled onto the foliage of Douglas fir or into bark crevices of Colorado blue spruce. FUNGUS GNAT - Nursery inspections in the last week found fungus gnats to be a common problem for greenhouse growers. These insects flourish in moist environments with decaying plant matter, making greenhouses ideal settings for infestations. The larvae feed directly on the roots of seedlings and potted plants and their injury to young roots promotes development of root and stem rots such as Botrytis, Pythium and Verticillium. Adult populations can be monitored with yellow sticky cards placed horizontally just above the growing media. Measures that reduce moisture, such as using proper watering techniques, selecting potting soil that drains well, and keeping floors free of soil and plant debris should help to minimize problems. SPIDER MITE - Damage to a variety of ornamentals was observed during greenhouse inspections in Jefferson, Racine and Washington counties. Symptoms of mite injury vary according to species and host plant, but usually include stippling, bronzing, mottling and chlorosis of leaves. The species most commonly found in greenhouse settings are the twospotted spider mite and cyclamen mite. Control of these mites and others depends heavily upon an understanding of their biology, so distinguishing between mite species is critical. THRIPS - This greenhouse pest was also noted during recent inspections. Affected plants were dahlia, gerbera daisy, New Guinea impatiens, primrose and passion vine, although greenhouse thrips have more than 100 different hosts. Their feeding results in stippled, silvery or bleached leaves and, in severe cases, yellowing and leaf drop. Similar to spider mites, control requires accurate identification of the species involved since some mites occur on many different plants but are considered damaging to only a few. -- Liz Meils, DATCP Nursery Inspector GYPSY MOTH - The annual trapping survey is scheduled to begin during the week of May 13 in southern Wisconsin and May 20 in the north. Approximately 19,000 traps will be placed in the western half of the state at densities of one trap per mile, one by two per mile, two per mile and three per mile. Delimitation traps to evaluate the effectiveness of last year's treatments or to identify reproducing populations will be set at a higher density of four traps per mile. Gypsy Moth Program specialists anticipate higher larval populations for Ashland and Bayfield counties, and possibly Clark and Jackson counties this year based on the results of egg mass surveys last fall. -- Chris Whitney, DATCP Gypsy Moth Trapping Coordinator 
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