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 #10
 
April 2, 2003
 
 
Disease:

Fusicoccum Canker
This canker is caused by opportunistic fungi that attack stressed ash trees, particularly drought-stressed trees, mechanically damaged trees, and trees on poor sites. Fusicoccum canker was seen last week on ash trees with just 1" - 4" of growth last year. The fungi are harmless to healthy ash.

The fungi spread by rainfall and mechanical means and invade bark through wounds. Cankers form between leaf drop in the autumn and breaking dormancy in the spring. The cankers may girdle branches causing limbs or the leader to die.

Prevention is best: avoid mechanical injury during planting, use proper pruning techniques, plant on good sites, and irrigate during dry periods. Remove affected areas during dry weather. Fungicides are not necessary or effective.

Source: Diseases of Woody Ornamentals and Trees in Nurseries. Jones and Benson, eds. APS Press.

 
Photo by Dr. Win Dunwell
Insect:

Asian Ambrosia Beetle
Continue to monitor for Asian ambrosia beetle. Of the hundreds of ambrosia beetle species, the Asian ambrosia beetle is particularly harmful, as can be the fruit-tree pinhole borer and tea root borer or smaller alnus bark beetle. Asian ambrosia beetles attack a variety of woody plants. These pests are not known to currently be a problem in Kentucky.

Asian ambrosia beetles are reddish-brown and have a bumpy surface on the tip of the abdomen. This granulated surface can be seen with a 10x hand lens.

Any suspicious specimens should be submitted for identification. Spray Astro at the first sign of infestation. Spray 2-3 times until plants are fully leafed out as the Asian ambrosia beetle prefers dormant plants.

Source: Commercial Insect and Mite Control for Trees, Shrubs, and Flowers. UT Pub. 1589.

 
Cultural:

Container Weed Control

Even with the below treatments being applied as often as 4 times a year (potentially costing $1040 per acre), hand weeding is still necessary. The efficacy of the herbicides will determine the total cost of weed control. Herbicides that provide good control will reduce total weed costs by reducing hand weeding. On average, it costs $0.42 per 3 gallon pot to control weeds by hand weeding alone compared to $0.17 per pot when herbicides are used. Weed control costs can be as little as $0.02 per pot when effective herbicides are used.

Herbicide
Price per acre
Price per 3 gallon pot per year
OH2
$182.00
$0.05
Regalkade G @ 0.75
$92.00
$0.03
Regalkade G @ 1.5
$185.00
$0.05
Regal OO
$178.00
$0.05
Snapshot TG
$260.00
$0.08
Treflan
$49.00
$0.01

It's Only Money! An Economic Comparison of Weed Control Options. 2001 NC Nursery Shortcourse.

 
Watering

The substrate your plants are growing in, weather, stage of growth, and container size all affect the frequency of watering, as does the volume of water and thoroughness of application. Growers with plants for pot and pot production currently growing above ground will want to monitor the moisture level. On a 17.5 gallon container feel the substrate approximately 4" deep to assess whether or not the plants need watered. While plants are dormant very little water will be required to keep the substrate moist. Once the plants begin to leaf out they use more water. Warm, sunny, and windy days cause the substrate to dry out more quickly. Media with more organic matter and less pine bark will hold moisture longer than mixes closer to 100% pine bark. No more than 25% of the volume of water applied should leach out. Overwatering wastes water and fertilizer. Underwatering can leave dry areas within the container and can lead to fertilizer salt build up.

Source: Best Management Practices for Producing Container-Grown Plants. Southern Nursery Association. 2000.


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