Disease:
Fusicoccum Canker on Ash - again!
Spores from the fungi causing Fusicoccum canker were identified from ash canker samples taken in April. The cankers were found on recently potted Cimmaron® ash bareroot liners. These cankers had a slightly different appearance from the Fusicoccum that was identified in March on the terminals of Cimmaron® ash trees beginning their second year of field production. (See Nursery Update #10.) While the canker was readily visible on the field grown trees, those on liners received this spring were difficult to see unless the bark was wet. Cankers had an orange cast with very distinct margins.

Cankers form between leaf drop in the autumn and breaking dormancy in the spring. The fungi that cause Fusicoccum cankers only attack stressed trees.

Photos:
Fusicoccum on recently received liners (top) and on second year ash trees in the field (below).

Insect:
Japanese Beetle
Japanese beetles will soon make their presence known in all but the far western portion of Kentucky. The beetles feed on over 300 species of plants causing severe skeletonization of leaves which reduces photosynthesis and detracts from the aesthetic value of the plants. Some plants that are particularly susceptible to Japanese beetle feeding are: crabapple, cherry, elm, grape, linden, Japanese maple, Norway maple, plum, sassafras, and roses. Smartweed is a highly preferred host plant and should be eliminated from field margins.

Traps should not be used as a control method in nursery blocks as only a portion of the insects will go into the traps, leaving the rest to feed on the surrounding nursery stock. If traps are used away from nursery stock they may be effective in reducing beetle numbers. Trap bags fill up quickly and need to be checked daily. Scouting preferred plants (linden or smartweed) is a better method of detecting Japanese beetle presence as there is no risk to attracting more insects. Controls should be applied when there are 10 leaves with 3 beetles per leaf. Check 4 branches. Once damaged a plant becomes more attractive and thus more prone to Japanese beetle attacks so Japanese beetle feeding should not go uncontrolled for long.

Spray drift
In the past few weeks Autumn Purple® white ash trees have been reported with spray drift symptoms. These ash trees have been in the same block as crabapples, maples, flowering plums, flowering cherries, and pussy willows, all of which have no symptoms. In one instance Amelanchier in the same block showed some spray drift symptoms, but different from the symptoms seen on the ash trees. The ash trees were not any closer to the field crops sprayed than other trees within the same block. The symptoms are yellow spots or yellow margins with white interiors, eventually turning necrotic. The trees only have damage on 30% of the leaves surface and appear to be outgrowing the damage.

Some questions arise: are ash trees, and specifically Autumn Purple® white ash, more susceptible to drift of certain chemicals? Were the ash leaves at a more tender stage than the other plants? I would like to hear from anyone experiencing this type of damage on ash trees.

Fertilizing
June is the time to reapply fertilizer to field production. Best Management Practices for Field Production recommend:

1st year: supplemental application if needed - 0.25-0.50 ounce of nitrogen per plant in the root zone as a sidedress.

2nd year: 0.5-1.0 ounce of nitrogen per plant, 2/3 at budbreak and 1/3 by mid-June.

3rd year and following years: 1.0-2.0 ounces of nitrogen per plant, 2/3 at budbreak and 1/3 by mid-June.

Notes:
Controlled release fertilizers may last all season. Urea has the highest nitrogen concentration and has the lowest salt index per unit nitrogen. For price comparisons of various fertilizers see the U.K. Agricultural Input Price Survey. Keep fertilizer away from the base of the trunk.

Source: U.K. Agricultural Input Price Survey; Whitcomb, C.E. Production of Landscape Plants II (in the field);NCSU Best Management Practices for Field Production.