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 #9
March 18, 2003

Prune out or remove plants with fireblight, black knot, or cedar apple rust.

Cedar apple rust teliospores may be found on eastern red cedar. Soon they will change from a brown, hard gall to a bright orange gall with octapus-like projections. A long-term control measure is to destroy or remove eastern red cedar in field margins.

Prepare upcoming control measures for scab, cedar apple rust, and fireblight on crabapple and black knot of Prunus sp.

Photo at right by Dr. Win Dunwell

Fireblight cankers are sunken with cracked edges.

Black knot on plum
Cedar apple rust teliospore
Eastern tent caterpillar eggs


Bagworms overwinter as eggs in old bags. Although the bag feels empty there are many eggs inside. Remove and destroy by hand when numbers are low, otherwise use chemical controls after egg hatch in May. Bagworms may be found on many species including deciduous trees. During nursery visits last week bagworm bags were found on callery pear.

Prune out eastern tent caterpillar egg masses from Prunus sp. in fields and from wild cherries in field margins before they hatch.

Shoot boring caterpillar on maple has not been a significant problem in Kentucky. Growers that need to control it can spray Talstar® when the second set of leaves are dime-sized.

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


Weed Control

If you haven't applied a preemergent herbicide, plan to do so before it is too late. For a preemergent weed control program to be effective the product must be applied before weed seeds begin to germinate. Preemergent herbicides should be applied to clean fields and rained in or irrigated following application. For trees in their second year of field production Princep® plus either Barricade®, Pendulum®, or Surflan™ are some herbicide options.

Avoid relying on glyphosate (Roundup®) products exclusively for weed control. Glyphosate accumulates in plants; plants have no method of breaking it down. The accumulated glyphosate has been implicated in causing large cankers along the trunk. Paraquat (Gramoxone-Super®), and glufosinate-ammonium (Finale®) have also been implicated in canker formation.

These herbicides are absorbed through the bark of young, thin-barked species that still have pigment in the bark. Trees don't exhibit herbicide injury for a year or two after application.

Injury from paraquat or glufosinate-ammonium appears as a sunken canker; healthy tissue grows up and around tissue that was injured. Glyphosate injury appears as a slit in the bark. Depending on the amount of herbicide intercepted by the bark and species sensitivity, the split may extend a few inches or few yards. Slits may be on any side of the tree, distinguishing herbicide damage from frost cracks.

Dr. Hannah Mathers. OSU. Understanding Failures in Ornamental Weed Control: Forget the Excuses!
Mary Ann Rose. December 1995. Tree Trunks, Bark, Cankers, and Frost Cracks. Nursery and Landscape Dialog.
Dr. Larry Kuhns. 1997. Controlling Weeds in Nursery and Landscape Plantings. PennState Pub.R5M500comm

Planting Tip

Remember to keep roots moist while planting. A tarp or moist burlap can be used to help hold in moisture while liners are on the transplanter or are waiting to get loaded onto the transplanter. Prior to planting, soak the roots. Avoid exposing liners to the sun and wind.

Harvesting Tip

The outer few inches of the root ball can contain 50% of the total soil volume. When this outer layer of soil is allowed to dry out half of the fine roots can be damaged. Take precautions to prevent the the rootball from drying out by putting harvested trees in shady areas out of the wind. Water as needed to prevent moisture loss.

Source: Watson and Himelick. 1997. Principles and Practice of Planting Trees and Shrubs.

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