Diseases:
Ash Leaf Spot
Two ash leaf spots have been recently diagnosed, Mycosphaerella effigurata and M. fraxini. Green and white ash are hosts of these fungi and no known resistant cultivars exist. The Mycosphaerella leaf spots are common in nurseries and cause premature leaf drop. Otherwise the leaf spots are considered cosmetic damage. (See Nursery Update #5 for more information on cosmetic diseases). At least one midwestern nursery has reported the early leaf drop to be beneficial.

Photo at top courtesy of Paul Bachi, U.K. Plant Disease Lab Diagnostician.

Sources: The USDA National Agroforestry Center; The Bugwood Network - The University of Georgia.

Black Knot
Black knot incidence has been recorded on plum liners at several nurseries. Check for an assessment of this information in the upcoming 2002 Nursery and Landscape Program Research Report. Those nurseries with purple-leaved plums may want to scout their fields and remove and destroy any remaining infected trees or infected branches to reduce fungal inoculum next season. See Nursery Update #2 for more on black knot.

Fall Preemergent Application
Preemergents may need to be applied in the fall for two reasons: to eliminate winter annual weeds that are hosts for soybean cyst nematode, such as henbit and chickweed; and, to create a longer window to plant and harvest before a spring preemergent application is necessary. In addition, thistle seed germinates in the autumn so a fall applied preemergent can provide some control of this noxious weed. Apply fall preemergents to freshly cultivated soil September through October.

Research by Dr. Robert McNiel has shown that some spring applied preemergents have enough carryover to control winter annuals. Predict 80WG at 7.2 lb. ai/A and Predict 80WG + Factor 65WG gave excellent control of chickweed 11 months after treatment. (Factor is now sold as Barricade.) Excellent control of henbit occurred using any combination including Factor 65WG or with Dimension IEC. Other herbicides and combinations of herbicides also provided control of henbit and chickweed.

Source: Winter Annual Weed Control by Spring Applied Preemergent Carryover U.K. research by McNiel, Weston, and Harmon; Field Nursery Weed Control by U.T. Area Nursery Specialist Mark Halcomb.

Oh Deer!
Deer typicaly cause two types of damage in nurseries: browsing and rubbing. Browsing damage occurs when deer eat the foliage, stem tips, and buds from trees and shrubs, and typically occurs in the winter and early spring. Browsing is often only damaging when the terminal bud is removed. Deer damage from rubs occurs in August in Kentucky as bucks rub the velvet from their antlers.

Deer browsing can easily be distinguished from rabbit damage. Deer often browse from top to bottom of a tree. Deer leave a rough, ragged looking tip where they chew off a stem. With their incisors, rabbits leave a clean 45 degree cut. Various repellents are effective at least for periods of time to control browsing. Those that are most effective have both a repellent odor and a repellent taste. Utilizing dogs, particularly at the field perimeter, or planting the perimeter with a more enticing crop such as crimson clover has worked for some nurseries. Be wary of planting a "trap crop" as it is essentially establishing a food plot and the crop could provide a host for Soybean Cyst Nematode. Harvesting (obtain a permit from the Ky. Dept. of Fish and Wildlife Resources) has also been successful. Fencing remains the best long-term solution. Depending on deer pressure fencing often pays for itself in 1-2 years.

To prevent the damage caused by rubs there is one additional option: using protective tubes around tree trunks. Unfortunately, nurseries in some parts of the country have found that cylindrical trunk guards aren't always substantial enough to protect against rubs.

For more information: U.K. Pub. FOR-57, Managing White-Tailed Deer Problems in Kentucky; Auburn Pub ANR-961, Controlling Deer In Our Nurseries And Landscapes; CSU Pub. 2301 Deer Control.