ANTHRACNOSE

 

This is a fungus that infects a wide variety of ornamental trees and shrubs. Commonly affected plants include Japanese maple, dogwood (both shrubs and trees), oak, oak leaf hydrangea, Boston ivy, willow, and sycamore.

 

Ornamental pink willow is very susceptible

 

It is also a very common disease of commercially grown fruit plants like strawberry, papaya, and apples.

 

SYMPTOMS

 

Symptoms are observed on flowers, leaves, fruit, and stems. These vary on their expression and intensity depending on the host species. They may include round purplish spots on leaves, floral buds, and flowers.

 

  Purple spots on leaves

 

Flowers may become mottled and deformed. Many times the spots merge or converge.  Most just drop quickly without even opening.

 

 Purple spots on flowers

 

On stems they gradually intensify in color until they turn blackish. Spots can merge one into another forming large scarred areas on stems and twigs.

 

Merging blisters on stems

 

LIFECYCLE 

 

This fungus thrives under cool and moist conditions – it is particularly active in Spring and Fall. Spores form inside infected leaves and stems and are released into the soil and air as the plant debris decays. Many are directly sent into the air environment from the blisters on leaves, stems and twigs. Spores may survive in the soil for a period of several years.

 

INFECTION 

 

Severe infections often lead to early and complete defoliation of entire trees and shrubs. Many times infected shoots will suddenly wilt and appear scorched. Everything above the infection dies. The lower on the stem the anthracnose attacks the more stem and leaves will perish.

 

Most tissue above the infection point will perish

 

TREATMENT

 

It is possible to control Anthracnose by regular applications of fungicide during the growing season. The sooner you treat it the better. Many untreated plants perish in winter – indirectly due to leaf loss and low sugar production from the summer.

However, the strongest deciding factors in the ability to ward off the disease – is the general health of the plant, and the stresses it is exposed to.  Containerized trees planted in poorly nourished soil invites trouble!  Improper watering habits, or placing plants in too low a light for them – makes them very susceptible.

 

Containerized maple tree is an Anthracnose target !

 

If you see any spots on your leaves – Call Plant Specialists TODAY !

Our experts that can tell if they are from Anthracnose!

They are also NYSDEC licensed applicators and can treat them too !!!

Don’t delay – the sooner the better !

 

GREENING NEW YORK FOR OVER 51 YEARS !

 

 

 

Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBA

All photographs used with permission @SHUTTERSTOCK