Lexington, Kentucky 40546
      
Nursery Update - A University of Kentucky Cooperative Extension Service update for the Kentucky Nursery Industry
   
By Amy Fulcher, Extension Associate - Nursery Crops
University of Kentucky Department of Horticulture
Update #21
April 2, 2004

Insects:
White Peach Scale and Oystershell Scale
- both visible now!
White Peach Scale (top) crawlers are active in May and continue through late summer. They are very destructive on many fruiting and flowering trees and shrubs. There are 3 generations per year.

Oystershell Scale (bottom) occurs on more than 128 plant species, most commonly: lilac, ash, willow, poplar, and maple. Large portions of trees and shrubs can be killed by the scale. The eggs overwinters under the female scale cover; crawlers are active in May when hawthorns begin to bloom.

Controlling scale is a long-term, 3 prong attack; chemical insecticides alone will not provide control. 1. Remove or severely prune affected plants and burn the clippings. 2. Apply dormant oil (on oil-tolerant plant species). 3. Apply pesticides when crawlers are active. Crawler emergence can be identified by wrapping double-sided tape around infested branches and routinely checking the tape for crawlers. Insecticidal Soap, Carbaryl, Malathion, Chlorpyrifos, and Orthene are control options.

Source: Insects That Feed on Trees and Shrubs, Cornell University Press; Oystershell Scale, UK Entfact 433; Commercial Insect and Mite Control for Trees, Shrubs, and Flowers, UT PB 1589.

 

Cultural:

UK Fertilizer Research Results

During 2002 and 2003 fertilizer experiments were conducted at the UKREC and at a production nursery, The Flower Potts.

Objectives: The objective of the research located at The Flower Potts was to examine the effect of fertilizer technology, fertilizer rate, method of application, and summer reapplication on the height, caliper, and number of branches of Amelanchier x ‘Autumn Brilliance’. Polyon® (a polyurethane coated fertilizer) 18-4-8 with minors, 8-9 month release and Osmocote Plus® (an alkyd resin coated fertilizer) N&S 15-9-12, 8-9 month release were the two control-release fertilizers tested. Fertilizer treatments were applied in March and included the two fertilizer technologies, the high and medium labeled rate of each respective fertilizer, and top-applying or incorporating. One half of the plants were also top-dressed in June with the corresponding 5-6 release month fertilizer.

Results: Whether or not the trees received a summer reapplication (topdress) had no significant effect on the number of branches, caliper, or height. No treatment had any impact on height. This likely reflects the heading back pruning that was done during the summer. The Osmocote Plus® treatments had more branches than the control (control=no fertilizer). Trees treated with the high rate of Osmocote Plus® had significantly greater caliper than those treated with the high or medium rate of Polyon® or the control. Incorporating the fertilizer significantly increased the caliper for the Polyon® treated trees, while topdressing significantly increased the caliper for the Osmocote Plus® treated trees.

Objectives: The objective of the research conducted at the UKREC was to determine the effects of fertilizing at two rates of Polyon® 18-5-10, 8-9 month release fertilizer for 7 taxa. The taxa tested were: Hedge Maple, Autumn Blaze® Maple, Renaissance Reflection™ Birch, ‘Spring Snow’ Crabapple, ‘Mt. St. Helens’ Plum, Chinkapin Oak, and Zelkova serrata. Two rates were used: the labeled medium rate, 100 grams (1x), and double the medium rate, 200 grams (2x). Caliper, height, leaf area, and chlorophyll levels were measured.

Results:
Fertilizing with the higher rate (200g) of fertilizer affected height, leaf color, and leaf size (see images below) for some taxa tested, but had no influence on caliper for any of the taxa tested. While plants are not sized and graded based on leaf size or color, these differences would be readily apparent to customers, particularly when the same taxa from multiple sources are displayed or stored in holding yards in close proximity.

 
Details of the research projects are available, call 270-365-7541 x 279.
      
Hedge maple
200 grams (l), 100 grams (r)

Chinkapin Oak
200 grams (l), 100 grams (r)

Autumn Blaze® Maple
200 grams (l), 100 grams (r)

 

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