What Causes Citrus Foot Rot: Controlling Citrus Gummosis In Gardens

What Causes Citrus Foot Rot: Controlling Citrus Gummosis In Gardens

By: Mary H. Dyer, Credentialed Garden Writer

Citrus foot rot, often known as gummosis of citrus or brown rot of citrus trees, is a major disease that wreaks havoc on citrus trees around the world. Unfortunately, citrus foot rot isn’t curable but you may be able to prevent it from taking over your citrus orchards. Read on to learn more about citrus gummosis problems and what you can do to prevent the disease from spreading.

Citrus Gummosis Information

What causes citrus foot rot? Citrus foot rot is a disease caused by Phytophthora, an aggressive fungus that lives in the soil. Phytophthora requires moisture to move to trees via rain, irrigation, or whenever spores splash on tree trunks. Trees can develop citrus root rot symptoms very quickly in rainy weather and cool, moist climates.

Citrus Foot Rot Symptoms

Citrus foot rot symptoms include yellowing foliage and leaf dieback, along with reduced yield and smaller fruit. The term “gummosis” isn’t the name of a disease, but actually refers to a major symptom in which a gooey, dark brown, gum-like substance oozes from cracks and lesions in the bark.

The water soaked, brownish or black lesions spread around the trunk, eventually girdling the tree. This may occur rapidly, or it may continue for several years, depending on environmental conditions.

Managing Citrus Gummosis Problems

Early detection of citrus foot rot is critical, but the initial signs may be difficult to spot. Here are some tips for managing gummosis of citrus:

Ensure the soil drains well. You may need to consider planting trees on berms to improve drainage.

Look closely at the bark of new trees before purchasing. Inspect citrus trees for symptoms several times per year.

Water citrus trees properly, using a drip system to avoid overwatering. Avoid irrigating trees with drained water, as Phytophthora can be moved from one area to another in soil runoff.

Limit mulching under citrus trees. Mulch slows drying of the soil, thus contributing to excess moisture and the development of citrus foot rot.

This article was last updated on

Read more about Citrus Trees


FOOT ROT GUMMOSIS - CITRUS

This is a well known disease in fruit trees. I am sharing with you my limited experience with gummosis on one of our Satsuma trees and how I am treating it.

In simple terms, foot rot gummosis in citrus occurs when zoospores splash into wound or bark crack around the trunk base. Zoospores travel thru rain and/or irrigation, contact the roots, germinate and cause root rot. They can affect other parts of tree but this discussion is limited to disease on citrus trunk bases.

Upon initial inspection I thought deer had damaged the trunk (and they may very well have wounded the tree) but excessive rains are probably more of a factor, encouraging zoospore travel. Once I noticed orangey sap oozing from the base I knew this needed further attention. It is a contagious disease so prompt attention is important.

Here are two pics of what the base of my Satsuma looked like:

Here are my tools, a scraper, thoroughly washed with Clorox and dried and a copper fungicide, available at HD.

The hardest part (not really hard) was to sit as close as possible to the base of the trunk so I could scrape all the soft and dead tissue, as well as any sap. I scraped until I felt firm tissue. In my case, there was not much scraping to do. After scraping, I thoroughly sprayed the area with the fungicide. Here are two pics of how the trunk looked post scraping

This message was edited Jul 20, 2016 2:44 PM

I will post an update on the success of my treatment of choice. My tree is under 10 years old and I saw no evidence of damage in foliage, branches, fruit--just the base of the trunk.

Here are two links I found useful when researching gummosis:

A final pic shows some of the sap removed from the trunk. It was hard are resin! I have lost the tag on my Satsuma, it could be Seto or Owari, not sure


Brown Rot a.k.a Foot Rot Gummosis Phytophthora on Citrus in the Low Desert

HOST: Citrus: sweet orange and rough lemon rootstocks are very susceptible

SYMPTOMS:

    Stunting, nutrient deficiencies, root has brown or black lesions, - The fungus can infect the trunks of any citrus killing the bark and causing a brown gummy discoloration of the cambium and an oozing of dark brown gum. Phytophthora can girdle the tree and causes death in a years time.

CAUSE:

    The fungus is everywhere in the soil. It requires moisture to move. As a water born fungus it enters the bark when standing water contacts the trunk of the tree.

MANAGEMENT:
Prevention

  • Use resistant rootstock. Sour Orange is highly resistant to Phytophthora however it is vulnerable to a disease carried by the brown citrus aphid which is projected to become a problem in the future. Avoid using rough lemon or sweet orange rootstock.
  • Select trees which have been grafted at least six inches above the soil line.
  • Control soil moisture
Treatment
  • Remove infected bark and a half inch border of healthy tissue. Treat the wound with a Bordeaux fungicide paste.
  • Apply Metalaxyl as a drench, this systemic fungicide will enter roots and kill Phytophthora in the soil and roots.

For additional information and images see AZ1154 Diseases of Citrus in Arizona


To Gardening and Landscaping in Maricopa County, AZ

Phytophthora on Citrus in the Low Desert
visitors since June 10, 1998 Last Updated May 26, 2005


Texas Plant Disease Handbook

Alternaria Stem-End Rot (Black Rot)

Fungal pathogen

Area(s) affected

Signs/Symptoms

Cracks in the stylar end of the fruit, or the bellybutton of the fruit, allow the fungus to enter and infect the fruit. Infected fruit will change color prematurely and may drop early from the tree. A light brown to black spot on the rind can be noticed near the stylar end of the fruit and when the it is sliced open one can observe the black rot inside the fruit.

For more information

Cachexia (Xyloporosis)

Causal agent

Area(s) affected

Signs/Symptoms

When the bark is peeled back one can observe smooth depressions in the wood which correspond to projections extending from the inner bark.

For more information

Citrus Greening (Huanglongbing)

Bacterial pathogen

Candidatus Liberibacter spp.

Area(s) affected

Signs/Symptoms

Infected trees may decline and eventually die. Fruit maybe small and lopsided. Irregular patterns of dark green, light green and yellow blotches (mottling) cross the veins of leaves and are asymmetrically displayed on the leaf blade. Infected leaves may be thicker and leathery compared to healthy leaves.

Photo credit: Florida Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org

For more information

Citrus Tatter Leaf

Causal agent

Citrus tatter leaf capillovirus, (syn. Citrange stunt virus)

Area(s) affected

Signs/Symptoms

Infected plants are usually symptomless. However, when symptoms are produced, one can observe leaf yellowing, leaf deformation, twig deformation, stunting, overblooming, and premature fruit drop. This virus also causes a bud-union crease, which can be seen when the bark is peeled back. One can observe a yellow to brown line where the scion and stock were grafted together.

For more information

Cotton Root Rot

Fungal pathogen

Phymatotrichopsis omnivora , (syn. Phymatotrichum omnivorum)

Area(s) affected

Signs/Symptoms

Infected plants die suddenly. Root bark is decayed and brownish, and bronze colored wooly strands of the fungus are frequently apparent on the root surface. Leaves will turn brown and remain attached to the branches.

For more information

Diplodia Stem-End Rot

Fungal pathogen

Diplodia natalensis , (syn. Physalospora rhodina)

Area(s) affected

Signs/Symptoms

This disease remains dormant while the fruit is still attached to the tree. Once the fruit is removed and put into storage, symptoms will be produced. The rind will first turn brown near the stem end of the fruit and then will progress down the fruit forming brown, finger-like streaks. The whole fruit will eventually turn black and give off a sour, fermented odor.

For more information

Causal agent

Citrus exocortis viroid (CEVd)

Area(s) affected

Signs/Symptoms

Infected rootstocks will be stunted and the bark at the crown of the tree will peel off, this is known as bark shelling. A gummy substance may also exude from the base of the trunk.

For more information

Fungal pathogen

Area(s) affected

Signs/Symptoms

Small black dots form on the rind near the oil glands. This causes the affected area to remain green when the fruit matures, or turns yellow. This does not affect the fruit or juice quality, only the fruit grade.

For more information

Fungal pathogen

Penicillium digitatum

Area(s) affected

Signs/Symptoms

Fruit injured during harvesting and handling may be infected by this fungus. The fungus enters the fruit only through wounds in the rind and these wounds soon turn to water soaked lesions. A white substance eventually forms on the lesion and as the lesion gets larger, the center will turn olive green and be outlined in white.

Photo credit: Gerald Holmes, Valent USA Corporation, Bugwood.org

For more information

Greasy Spot

Fungal pathogen

Area(s) affected

Signs/Symptoms

Yellow to dark brown to black spots form on the underside of the leaf. As these spots darken, corresponding yellow spots will form on the upper leaf surface. Leaves may drop prematurely. If the fruit is infected, small black spots will form on the rind and the surrounding area will remain green longer.

Photo credit: Don Ferrin, Louisiana State University Agricultural Center, Bugwood.org

For more information

Heart Rot/Wood Rot

Fungal pathogen(s)

Area(s) affected

Signs/Symptoms

At the base of infected trunks, brown to reddish-brown, fan-shaped structures can be observed. This infection causes internal wood rot and the affected tree will eventually decline or die.

For more information

Citrus Leafminer

Phyllocnistis citrella

Area(s) affected

Females lay larvae singly on the underside of the leaf. After the larvae hatch they begin to feed in shallow, serpent-like tunnels in the leaves. The tunnels are filled with frass, or excrement. Affected leaves will curl and be distorted.

Photo credit: Whitney Cranshaw, Bugwood.org

For more information

Fungal pathogen

Area(s) affected

Signs/Symptoms

Small, brown spots surrounded by a yellow halo form on the leaf surface. As the disease progresses, a gummy substance exudes from the spot, dries, hardens, and gives the leaf a sandpaper texture. Leaves may drop prematurely.

Small, brown to black raised spots form on the fruit surface. If these spots coalesce they form an irregular, cracked pattern known as “mudcake melanose.” Sometimes these spots develop in a tear-streaked pattern known as “tear-stain melanose.”

Photo credit: Cesar Calderon, USDA APHIS PPQ, Bugwood.org

For more information

Physiological Disorders

Causal agent(s)

Wind, strong sunlight, nutrient deficiencies, herbicide toxicity

Area(s) affected

Firing: wind desiccation

Leaf Yellowing: Magnesium, iron or zinc deficiencies and herbicide injury.

Oleocellosis: Peel oil is released when rind cells have been injured as a result of abrasion or rough handling. Sunken spots form on the rind.

Spray Burn: The fruit has a dry, brown sunken spot.

Sunscald: When the undersides of leaves are exposed to direct sunlight, irregular, brown, raised spots may be observed.

Wind Scar: This damage occurs as the result of twigs or leaves rubbing against young fruit

For more information

Phytophthora Diseases

Fungal pathogen(s)

Phytophthora citrophthora , P. parasitica, and other Pytophthora spp.

Area(s) affected

Signs/Symptoms

Brown Rot: The low-hanging fruit become infected first and then water will disseminate the fungus to fruit higher in the tree. Light brown lesions will form on the rind. As the disease progresses, in humid conditions, a white velvety growth can be observed on the rind and the fruit will give off a pungent, rancid odor.

Feeder Root Rot: The fungus infects the cortex of feeder roots, giving the root system a stringy appearance. This can lead to yield loss and a general prolonged tree decline.

Foot Rot/Gummosis: Infection of the trunk results in a dark, water-soaked areas, often with profuse exudation of a dark resin from the lesion. The dead bark frequently sloughs off the wood in vertical strips. If the lesion encircles the trunk, girdling occurs, leading to the death of the tree.

For more information

Rio Grande Gummosis

Fungal pathogen

Physalospora rhodina , (syn. Diplodia natalensis) and several other factors

Area(s) affected

Signs/Symptoms

Blisters on the trunk exude a pale yellow, gummy substance. The wood beneath infected tissue is pink to orange in color. Gum pockets may form.

For more information

Citrus Rust Mite (Silver Mite)

Phyllocoptruta oleivora

Area(s) affected

Signs/Symptoms

Mites feed on the fruit destroying the rind cells. When the fruit is green destroyed cells turn black (“bronzing”) and when the fruit is mature destroyed cells turn rust brown and are rough to the touch (“sharkskin”).

Photo credit: Don Ferrin, Louisiana State University Agricultural Center, Bugwood.org

For more information

Psorosis (Scaly Bark)

Causal agent

Area(s) affected

Signs/Symptoms

Leaves may exhibit yellow irregular flecks, blotches or round spots. Fruit may exhibit a yellow ring shaped pattern on the rind. Trunk and limbs will exhibit bark scaling or flaking, where the bark sloughs off. A gummy substance may form around the bark lesions, impregnating the wood, eventually leading to the rapid decline of the tree. The tree will become unproductive.

For more information

Slow Decline

Causal agent

Tylenchulus semipenetrans

Area(s) affected

Signs/Symptoms

The nematode feeds on the roots causing aboveground symptoms: canopy thinning, lack of vigor, poor fruit production, small leaf and fruit size, and exposure of bare crown limbs.

For more information

Fungal pathogen

Area(s) affected

Leaves, fruit and branches

Signs/Symptoms

Leaves, fruit and sometimes branches have a black, moldy appearance. The fungi causing sooty mold do not actually infect the plant, instead they grow on the sugary exudates (honeydew) of insects such as aphids, brown soft scale, blackflies and whiteflies. This can cause premature leaf drop and stunting of the tree.

Photo credit: Don Ferrin, Louisiana State University Agricultural Center, Bugwood.org

For more information

Sweet Orange Scab (SOS)

Fungal pathogen

Area(s) affected

Signs/Symptoms

Tan to gray, corky, wart-like scabs will form on the fruit rind.

Photo credit: Corinne Rhodes, Texas A&M University

Photo credit: Corinne Rhodes, Texas A&M University

Photo credit: Corinne Rhodes, Texas A&M University

For more information

Tristeza (Quick Decline)

Causal agent

Area(s) affected

Signs/Symptoms

The symptoms produced depend on the variety of plant, environmental conditions, and the virus strain. The virus can cause the tree to decline, leading to tree death. There are three distinct syndromes of the disease: quick decline, stem pitting, and seedling yellows. Leaves will exhibit yellow flecking, leaf cupping, and light green to yellow leaf veins. Fruit quality and size will be reduced. Branches and trunks will exhibit pitting, and if it is serious they will take on a ropey appearance.

Photo credit: L. Navarro, Instituto Valenciano de Investigaciones Agrarias, Bugwood.org

For more information

Twig Dieback

Fungal pathogen

various fungi, as well as other factors

Area(s) affected

Signs/Symptoms

Fungal infection often occurs following a freeze or mechanical or chemical injury. Affected young branches die back from the tip, sometimes producing gum exudation. Wood discoloration under the bark maybe observed.


Watch the video: See how Potato Late Blight develops