Common Plant Diseases

Design and InstallationGarden CareIndoor plantsPlant Health Care

Nov 12

Introduction

Plants are subject to disease and attack by pathogens just like any other organism on the planet. Diseases are biological organisms that affect plants inside their tissues. They are endoparasites. There are many types and come in many shapes and forms.The scientific study of diseases caused by pathogens is called Plant Pathology or phytopathology.

SCARY telial horns of Cedar Apple Rust disease

Symptoms

Plant appearance can give a clue regarding the type of pathogen involved. A symptom of disease is a visible effect of on the plant. These may include a change in color, shape or function. Most of the time, you rarely get to see the pathogen directly.For example, when you look at powdery mildew on a lilac leaf, you’re actually looking at part of the organism itself. It causes leaf deformation and necrotic spots.Common bacterial symptoms also cause brown, necrotic spots - but usually surrounded by a bright yellow halo.Bacterial canker of stone fruits causes gummosis, a thick sticky exudation that explodes out of the stems and trunks.Leaf wilting is a typical symptom of verticilium – usually seen in Dahlias.

wilts actually occur in upper branches because the fungus has invaded and blocked all the water carrying vessels in the stem with its dark black secretions

The Bad Guys

Most plant diseases – 85 percent – are caused by fungal or fungal-like organisms.

However, there many more that cause serious diseases of plants. These include oomycetes, bacteria, viruses, viroids, and phytoplasmas. I bet you didn't know there were so many types !

Bacteria

This is a primordial organism with a cell wall that has a simple genetic and chemical make Up. Incapable of repairing its own DNA thus subject to mortal damage by UV light rays.

microscopic pseudomonas - will devour the plant from the inside

bacterial Erwinia disease of dogwood flowers causes spotting and necrosis

Fungi

These are an ancient group of organisms more closely related to animals than plants. We know this because they contain the animal protein chitin. They reproduce both sexually and asexually via spores. These may be spread long distances by air or water, or they may be soil borne. Most will prefer shaded locations away from solar UV rays which are deadly to them.

Some colonize living plant tissue and obtain nutrients from living host cells – we call them biotrophic. Necrotrophic fungal pathogens as those that infect and kill host tissue and extract nutrients from the dead host cells. These are the worse!

Common powdery mildew

cedar apple rust pustules on apple leaf

Oomycetes

The oomycetes are fungus-like organisms. They include some of the most destructive plant pathogens known including the genus Phytophthora, which are responsible for root rot.

Despite not being closely related to the fungi, the oomycetes have developed similar infection strategies. They are capable of using proteins to turn off a plant's defenses in its infection process.

root rot

Slime molds

Some slime molds cause important diseases, including club root in cabbage and powdery scab in potatoes. These are caused by species of Plasmodiophora and Spongospora, respectively.

club root in Cabbage - where are all the numerous fine roots !!

Phytoplasmas

A group of organisms descendant from Bacteria that have a cell membrane surrounding them but no cell wall. They are parasitic in nature. Some genera are related to the mycoplasmas, which are human pathogens.They tend to have smaller genomes than most other bacteria and are transmitted by sap-sucking insects like aphids - being transferred into the plant's tissue where it reproduces.

abnormal pistils and stamens in a rose - the deformation is called phyllody

Viruses

Very primitive organism with a simple protein cover surrounding one strand of DNA. Usually incapable of living outside a host cell.

mosaic virus causing bleached tissue and deformation

do you see some suspicious looking symptoms in your garden plants ?

call Plant Specialists today !

Our Plant Health Care team is well versed in diagnostics

and treatment of the common plant diseases.

We know pathogens !!!!!

PLANT SPECIALISTS

GREENING NEW YORK FOR OVER 52 YEARS !

Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBAAll photographs used with permission @SHUTTERSTOCK

Peter Morris

Peter was born and raised on a beautiful green island in the midst of a tropical rainforest. He was introduced into the world of plants at the age of six when his grandmother, an avid Spanish gardener herself, asked him to help her grow seeds for her pepper garden. He was hooked! By the time he was a teen, he had his own rose and orchid collection numbering in the hundreds. Botany was in his blood, and that is what he set out to study.

His passion brought him to NY in the late seventies to further his education. His tenacity allowed him to work full time at Plant Specialists while he completed a MS in Plant Biology. As a manager at the time he felt unsatisfied with his knowledge of business and business processes. Peter felt compelled to learn, so he then pursued and completed an MBA in Quality Management within a few short years.

Peter’s other passion is teaching. His natural ability is quickly consumed by our staff in all subjects in Botany, Horticulture, and Landscaping. He created an immense reference library of more than 3,500 plants providing an invaluable resource for our staff.

Peter’s breadth of knowledge and wisdom allows him to effectively diagnose the needs of plants. Sometimes just by walking into a garden he can create a prescription that fixes even the hardest issue. He is our Staff Botanist, Diagnostician, and all around Mentor. Recently, he has put his immense knowledge and skills into developing a new department that focuses on Plant Healthcare. As he puts it, “Magic through Science”. The PHC staff that surround him have avidly consumed his teachings. Substantially developing their own plant wisdom, many have taken on difficult plant health issues with spectacular results.

Plant Healthcare has been an instant success with customers! The proper treatment of insects and diseases including Organic methods has made pest control a necessity for every plant. Correcting hormonal imbalances caused by planting in containers or refurbishing soils leached of nutrients by irrigation systems are big challenges PHC has become quite comfortable addressing. The scientific approach to the complex demands of keeping plants healthy in our harsh city environment has made many a customer say WOW!

Common Plant Diseases

Introduction

Symptoms