Peach Canker & Oozing Sap

Oozing Sap Coming from Peach Canker?  It might be a Fungal Disease.

Perennial canker of peach is a fungal infection of fruiting twigs, scaffold limbs, or trunks (Fig 1 & 2).  The disease may also be referred to as Cytospora canker, Leucostoma canker, perennial canker, valsa canker, or peach canker.  A common symptom is oozing gum from canker sites, so symptoms may also be referred to as gummosis (Fig 1). 

The causal fungi, Leucostoma spp., are weak pathogens that infect stressed or wounded plants.  Infections cause cankers, or stem lesions, that enlarge every year, creating annual rings or target-like growths.  These cankers expand until limbs become girdled and die.  Cankers often ooze gummy sap (gummosis) that eventually hardens (Fig 1).

Figure 1 – Perennial canker of peach limb, advanced symptoms with oozing sap. (Photo Penn State)

 

Gummosis can also be caused by other plant injuries such as bacterial infection (bacterial canker of peach), boring or sucking insects, and mechanical damage.  It is important to properly diagnose the cause of gummosis before considering management options. 

The fungi that cause peach canker produce spores during spring.  Fungal spores ooze from cankers during cool rainy weather.  Consequently, disease is often more severe during rainy years. 

Figure 2 – Infection of peach twigs, early symptoms.  (Photo West Virginia University)

 

Prevention of peach canker begins with vigorous plants and proper orchard sanitation. 

·        Retain plant vigor.  Maintain soil moisture, fertilize according to soil tests, and mulch properly. 

·        Avoid plant wounds such as mower damage, sunscald, winter injury, and insect injury.

·        Make clean, sharp pruning cuts that heal quickly.  Avoid jagged cuts.

·        Prune peach trees during late winter, preferably during late-February or March.

·        Prune during dry weather, only.  Fungal spores spread during wet conditions.

·        Maintain a clean orchard by pruning dead and damaged wood.  Remove cuttings from the orchard; bury, burn, or move them at least 100 yards from peach plantings.

·        Some peach cultivars are less susceptible to peach canker than others.  Use resistant or tolerant trees when possible.

 

If peach canker becomes a problem in the orchard, a strict sanitation should be implemented.  There are no fungicide treatments available for management of peach canker. 

·        Remove diseased twigs and limbs, making clean cuts at least 6 inches below cankers.  Remove diseased cuttings from the orchard.

·        Infected trunks may require “surgery.”  Using a knife or chisel, remove bark at least one inch around each disease lesion.  There is no need to cut into hardwood.  Do not paint affected area with wound dressing, paint, or oil. 

·        Prune during dry weather, only.

·        Disinfest pruners and tools between cuts using a commercial sanitizer, 10% bleach, or 10% Lysol® concentrated disinfectant.

·        Apply fungicides to open pruning wounds as a preventative.  Captan, iprodione (Rovral), and thiophanate-methyl (Topsin M) may be applied after pruning (delayed dormant phase), after petal fall, and after shuck split to prevent new infections. 

 

Sanitation and increased plant vigor are the primary disease management options for peach canker.  Growers should be aware of potential risks for infection and prevent disease outbreaks by following the guidelines above.  Once trees become infected, the pathogen can spread through orchards in just a few years.  Fungicides do not cure peach canker, and cultural practices are the primary means for disease management.

Boxwood Blight - Memorable Tips for Easy Identification

This weekend, the local Lexington newspaper, the Herald Leader, published a story on boxwood and boxwood blight.  Thus, I anticipate an influx of suspect samples and concerns.  Also, as weather becomes cooler and more rain is upon us, it is possible that the disease may appear in Kentucky this fall.  Below is a refresher on this devastating disease:

Boxwood blight (Cylindrocladium buxicola) was reported in southern Ohio this spring, but has yet to be found in Kentucky.  Nursery growers in the northern counties are especially concerned about movement of the disease across state lines. 



Figure 1 & 2.  Boxwood blight is most easily recognized by leaf drop.  Photos by Kelly Ivors, NC State.

 

Symptoms of boxwood blight are different from some of the most commonly observed boxwood problems.  For example, stem blight and drought damage result in foliage turning bright bronze or straw-colored while remaining intact.  Boxwood blight, in contrast, results in rapid defoliation of plants (Figure 1& 2).  Another distinguishing symptom of boxwood blight is brown stem lesions that are easily recognized after leaf drop (Fig 3).  Earliest symptoms include leaf spots, but these spots often go unnoticed unless a persistent scouting program is in place (Figure 4).  Roots are not affected.

Figure 3.  Brown stem lesions, a distinguishing characteristic of boxwood blight, are often noticed after leaf drop.  Photo permission by Kelly Ivors, NC State.

 

Avoid unhealthy plants at all costs.  Homeowners should examine plants carefully before purchase, avoiding plants with leaf or stem lesions or an unhealthy appearance.  Growers should carefully inspect incoming plants and liners before introducing them into production areas. 

Cultural practices can help prevent conditions that are conducive for the fungal pathogen.  Space plants for air circulation and rapid drying of foliage.  Overhead irrigation should be avoided.  Fungicides are not available for management of boxwood blight.  Infected plants must be destroyed by burning or burying.

Figure 4.  Leaf spots, the earliest symptoms of boxwood blight, can be detected by scouting.  Photo permission by Kelly Ivors, NC State.

 

Report suspected cases of boxwood blight immediately to your local Extension agent or specialist or to the UK Plant Disease Diagnostic Lab. 

Figure 5.  Comparison of boxwood blight to Volutella stem blight and Macrophoma blight.