Scab is the most common fungal disease on Pecan trees. Fungal diseases like Hypoxylon cankers and Wood rot/Heart rot can also infect Pecan trees. Fungal infections like Vein spot disease, Liver spot disease, and Anthracnose affect the appearance of the leaves mainly.
Pecans are the only nuts that are commercially produced in the US. One can understand their importance in the lives of the farmers.
A wide variety of fungal pathogens infect Pecan trees. The best way to prevent fungal infections in Pecan trees is by following disciplined cultural practices.
Black Spots on Pecan tree leaves
Black spots on Pecan tree leaves are caused by a fungal pathogen called Cladosporium caryigenum. This disease affects the nuts and leaves at many points in the life of the tree.
Pecan Scab disease is the most prominent disease of Pecan trees. Pecan tree scab damages the plant a lot, especially in the growing season when the tree buds.
Many, small, dark spots form on the leaves and the fruits of the infected Pecan tree. Such black spots eventually enlarge to engulf the entire leaves and fruits.
Pecan scab treatment
The best way to cure scab in Pecan trees is by spraying fungicides. There’s no organic spray to treat scab disease in Pecan trees.
You may need to apply fungicides a couple of times for it to be effective.
In the 1920s people used to spray Bordeaux mixture (copper sulfate and hydrated lime) on the infected plants. It worked wonderfully.
I advise you to spray the susceptible Pecan early in the growing season, as it’s best to prevent the disease rather than cure it.
Best Fungicide for Pecan Scab
Fungicides like Enable 2F/Propimax 3.6F work wonders to prevent Scab disease in Pecan trees. Agri-Tin 4L/Super-Tin 80WP also can prevent Scab disease in Pecan trees.
Use Super-TIn 80WP as the pre-pollination spray and Propimax 3.6F as the cover spray. Do the same with Enable 2F and Agri-Tin 4L.
Spray your Pecan tree as suggested to prevent the fungal spores from developing resistance to the fungicides.
When should I spray my Pecan tree for Scabs?
The first spray for the Pecan scab should be the pre-pollination spray. You need to do this in early April as a preventative measure.
One needs to follow a proper schedule to tackle Pecan scabs efficiently. Cover sprays are needed to protect the valuable produce from scab disease.
Primary spores are produced in the spring season from overwintering stromata on twigs. and nut shucks.
How to prevent Pecan Scab
You need to follow certain control methods to prevent Pecan scab disease. Below are some of the cultural control methods I follow to prevent Pecan Scab.
- Plant resistant varieties.
- When planting your orchard space the plants generously prevent Scab diseases. You need to make sure the tree gets enough sunlight and ventilation.
- Do not wet the leaves when watering your Pecan tree.
- Dispose of the fallen nuts, leaves, husks, and twigs from around the plant to prevent spore buildup.
Will Pecan Scab kill my tree?
No, Pecan Scab won’t kill the infected tree. The disease harms the tree severely but not so much that it kills the tree.
However, if left unmanaged, it can severely weaken the tree over time, making it more susceptible to other diseases, environmental stressors, and reduced nut production.
Fungus on Pecan tree trunk
The fungal outgrowths you see on the Pecan tree trunk are called hypoxylon cankers. This disease is caused by a fungal pathogen called Hypoxylon atropunctatum. If mushrooms are growing on the tree trunk, it is due to a disease called Heart rot/Wood rot.
Hypoxylon cankers in the Pecan tree
The Pecan tree sloughs off the infected bark from the tree revealing a powdery-reddish substance on the wood. This is the primary/early symptom of Hypoxylon infection.
Brownish-black crusty growth forms on the infected parts of the Pecan tree. These are called the Hypoxylon cankers.
Hypoxylon canker formation is favored by wounds. Try not to wound your Pecan tree unnecessarily. Seal the open wounds with a Tree Wound Pruning Sealer.
By sealing the wounds with a pruning sealer you can keep the fungal spores at bay.
Heart rot/Wood rot in the Pecan tree
Heart rot/Wood rot infects the Pecan tree when the tree gets damaged by improper pruning or mechanical damage by the winds.
The fungal spores enter the Pecan tree through these wounds. Symptoms may take several years to appear from the time of infection.
An early sign of the infection is the rotting of the infected Pecan tree’s wood. Infected tree’s branches and the trunk become weak.
Mushrooms grow in the wounded parts of the trunk and die-back occurs. After this stage of the disease, the tree dies.
Prune off the infected branches of the Pecan tree with a pruning saw as soon as you notice the symptoms. Your Pecan tree might recover if you cut off the infected parts proactively.
To prevent this fungal infection treat the wounds on your Pecan tree with an asphalt-based dressing.
Moss growing on the Pecan tree
Ball moss is an epiphytic plant that grows in the inner limbs of the Pecan tree. Spanish moss also grows on Pecan trees.
Ball moss on the Pecan tree
Ball moss doesn’t damage the Pecan tree in any way. Ball moss just uses the Pecan tree as the substratum. Ball moss doesn’t absorb/steal the nutrients/water from your Pecan.
Some people think that if the Ball moss spreads vigorously on the Pecan tree, it might obstruct the sunlight. So, get rid of the Ball moss only if it covers a great portion of the tree.
Spanish moss on the Pecan tree
Spanish moss is an epiphytic plant that appears like whiskers on the tree trunk/branches. Spanish moss just uses the Pecan tree as a support and doesn’t steal nutrients from the tree.
Spanish moss only becomes a problem if it grows vigorously obstructing the growth of nuts. If the Spanish moss becomes too heavy it could break the branches of the Pecan tree.
How do you get rid of moss on Pecan trees?
You can get rid of the Spanish moss/Ball moss using a long-handled rake/stick with an end-hook. Spray water on the moss forcefully first.
Get rid of the remaining moss using the rake. Do not let the weight of the wet moss harm your Pecan tree, get rid of the moss before the rainy season.
A mixture of baking soda and water works well to eliminate Spanish moss/Ball moss on your Pecan tree. Ask your local Arborist for advice.
Do not spray the baking soda mixture if there are smaller plants in the vicinity. If the trees are tall and out of reach, hire an arborist or a tree company with a bucket truck.
Note: Ball moss/Spanish moss is a fine habitat for many types of beneficial insects. So, think about this before you get rid of moss on the Pecan tree.
When do you spray Zinc on Pecan trees?
Spray Zinc formulations on Pecan trees that are suffering from Zinc deficiency. Zinc deficiency causes ‘Rosette’ disorder in Pecan trees.
This happens when the soil is alkaline or low in Zinc content. Zinc deficiency is seen in the leaves of the Pecan tree.
Affected leaves become twisted and turn reddish-brown. The twisted leaves and limbs die, starting from the top of the branches.
Initially, dieback is seen in the leaves and limbs of the tree. Eventually, the entire tree dies if left unattended.
Amend the soil by adding Zinc chelate formulation or Zinc sulfate to it. You can also spray Zinc formulations directly on the foliage of the affected Pecan tree.
Fungal leaf diseases in Pecan trees
A variety of fungi deform the leaves in Pecan trees. Anthracnose, Vein spot disease, and Downy spot disease are the main fungal leaf diseases in Pecan trees. Let’s see how to fix them.
Vein spot disease in Pecan tree
Vein spot disease is the most common fungal leaf disease in Pecan trees. Vein spot disease is caused by a fungal pathogen named Gnomonia nerviseda.
Vein spots are very similar to the spots of Scab disease. But this disease can easily be differentiated from Scab disease.
Vein spots only appear on the foliage of Pecan trees, unlike Scab where the spots appear on both nuts and leaves.
The spots only appear along the midrib/veins of the leaves. Fungus thrives in the debris on the ground, so it is a good idea to keep the surrounding area clean.
Plant resistant varieties like Melrose and Cherokee if possible. If the infection is in an early stage, cut off the affected leaves with pruning shears.
Fungicides that can treat Pecan scab work wonders for Vein spot disease too. Spray fungicide early in the season and again just before the fruiting season.
Liver spot disease in Pecan trees
Liver spot disease is caused by a fungal pathogen Gnomomia carvae. The first signs of the disease show themselves in May/June.
Circular, brown-colored spots appear on the lower sides of the leaves, on the midrib. The spots turn Cinnamon brown/liver-colored in the late summer season.
The infected Pecan tree loses a lot of leaves, especially in the wet season. Try to keep your Pecan tree healthy to avoid running into such infections.
Water and feed your Pecan tree on time to keep it in good condition. Scab fungicide sprays work well to treat Liver spot disease.
Downy Spot in Pecan Trees
‘Downy spot’ is a fungal leaf spot disease caused by the pathogen Mycosphaerella caryigena. The infected Pecan tree loses a lot of leaves.
Downy spot disease can be identified by the yellow spots that appear on the lower side of the leaves. This is the early symptom of the disease.
As the disease progresses, the spots turn brown and appear on the upper side of the leaves.
If the tree is severely infected then it loses its vigor. The infected Pecan tree loses a lot of nuts, causing monetary loss to the farmer/owner.
Spores of the fungus survive the winter in the leaf debris.
Zonate leaf spot disease in Pecan trees
Zonate leaf spot disease is caused by a fungal pathogen Cristulariella moricola. The disease causes defoliation of the Pecan tree in July and August(US).
Gray-colored spots appear on the uppersides of the Pecan tree leaves. Circular formations(tan/light brown) can be seen on the lower side of the leaves.
Infected leaves dry out and fall off by the late summer season. Symptoms are more pronounced after the wet summer months.
There are fungicides that can treat Zonate leaf spot disease in Pecan trees.
Anthracnose in Pecan trees
Shiny, brown sunken spots/blotches appear on the green Pecan fruits. Pink-colored masses may appear on the sunken lesions if the external conditions are wet.
Cream/Salmon colored circular lesions may appear on the sunken spots of the shucks. Chances of the disease increase with frequent rainfall.
Apply fungicides regularly to avoid a disease breakout. Dispose of the dead shucks and leaves as soon as you see them.
Planting resistant varieties can be a wise way to avoid running into this disease.
Brown spot disease in the Pecan tree
Brown spot disease is caused by a fungal pathogen Cercospora fusca. The symptoms of the disease are seen on the leaves in June/July.
If there is high rainfall/humidity, Pecan trees become highly susceptible to Brown spot disease. Small spots are first seen on the lower side of the leaves.
These spots enlarge to become brown spots/blotches with a gray cast. The infected Pecan tree loses the bulk of its leaves in a couple of months if it isn’t treated.
Brown spot is often confused with Gnomonia leaf spot disease. In Brown spot disease the spots are formed on the veins and also outside the veins.
In Gnomonia leaf spot the spots form only on the veins. Care well for your tree by watering and feeding it on time to prevent this disease.
Fungicides that work on Scab also can treat this disease.
Happy Gardening 🙂