List of pecan diseases facts for kids

Pecan trees (Carya illinoinensis) are well-known for their delicious nuts. But just like people, these important trees can get sick. This article will tell you about some common problems that can affect pecan trees, from tiny germs to things missing from their diet. Understanding these issues helps keep pecan trees healthy and producing lots of nuts!

Tiny Germs: Bacterial Diseases

Bacteria are tiny living things that can cause problems for plants. When pecan trees get bacterial diseases, it can make them weak or stop them from growing well.

What is Crown Gall?

Crown gall is a plant disease caused by a type of bacteria called Agrobacterium tumefaciens. This bacteria makes the tree grow strange, lumpy growths, or "galls," usually on the roots or near the base of the trunk. These galls can make it hard for the tree to get water and nutrients.

Understanding Pecan Leaf Scorch

Pecan bacterial leaf scorch is another bacterial problem. It's caused by Xylella fastidiosa. This bacteria blocks the tiny tubes inside the tree that carry water. When this happens, the leaves can't get enough water, and they start to look "scorched" or burned around the edges.

Fungi: Common Tree Troubles

Fungi are a big group of living things that include molds, yeasts, and mushrooms. Many fungi can cause diseases in pecan trees, affecting their leaves, branches, roots, and even the nuts themselves.

What is Pecan Scab?

Pecan scab is one of the most common and serious fungal diseases for pecan trees. It's caused by the fungus Fusicladium effusum. This disease creates dark, spotty lesions on leaves, twigs, and the pecan nuts. If a tree gets a bad case of scab, it can reduce the number and quality of nuts.

Spotting Leaf Problems

Several fungi cause different kinds of spots on pecan leaves:

• Anthracnose: Caused by Glomerella cingulata, this can lead to dark, sunken spots on leaves and sometimes twigs.
• Brown leaf spot: Sirosporium diffusum causes brown spots that can make leaves fall off early.
• Downy spot: Mycosphaerella caryigena creates small, yellow-green spots on the underside of leaves.
• Gnomonia leaf spot: Gnomonia dispora makes small, angular spots on leaves.
• Leaf blotch: Caused by Mycosphaerella dendroides, this leads to larger, irregular blotches on leaves.
• Septoria leaf spot: Septoria caryae causes small, circular spots, often with a darker border.
• Zonate leaf spot: Grovesinia pyramidalis creates spots that look like targets or rings on the leaves.

Root and Trunk Issues

Some fungi attack the roots or main trunk of the pecan tree, which can be very damaging:

• Clitocybe root rot: Caused by Armillaria tabescens, this fungus attacks the roots, making them rot. This can weaken the tree and even kill it.
• Cotton root rot: Phymatotrichopsis omnivora is a serious fungus that rots the roots, especially in warmer climates.
• Heart rot: Schizophyllum commune causes the inner wood of the tree trunk to decay, making the tree weak and unstable.
• Violet root rot: Helicobasidium brebissonii causes a purple-colored rot on the roots.

Other Fungal Concerns

• Powdery mildew: Microsphaera penicillata makes a white, powdery coating appear on leaves and young shoots.
• Pink mold: Trichothecium roseum can sometimes grow on pecan nuts, especially if they are damaged or stored improperly.
• Twig die back: Botryosphaeria dothidea causes branches and twigs to die back from the tips.

Tiny Worms: Parasitic Nematodes

Nematodes are microscopic roundworms that live in the soil. Some types are parasitic, meaning they feed on plant roots. This can hurt the tree's ability to take in water and nutrients.

Understanding Root Knot Nematodes

Root knot nematodes (like Meloidogyne arenaria, Meloidogyne incognita, Meloidogyne javanica, and Meloidogyne partityla) are a big problem. They invade the roots of pecan trees and cause them to swell up into "knots" or galls. These knots make it hard for the roots to work properly, stunting the tree's growth.

Ring Nematodes

Mesocriconema xenoplax is a type of ring nematode. These nematodes feed on the outside of the roots, causing damage that can slow down the tree's growth and make it less healthy.

Plant Diseases Caused by Phytoplasmas

Phytoplasmas are very tiny bacteria-like organisms that live inside plants. They can cause diseases that change how the plant grows.

What is Bunch Disease?

Bunch disease in pecan trees is caused by a type of Phytoplasma. This disease makes the tree grow many small, weak shoots in a "bunch" instead of strong, healthy branches. It can make the tree look bushy and stop it from producing good nuts.

Other Pecan Tree Problems

Sometimes, pecan trees have problems that aren't caused by bacteria, fungi, or nematodes. These can be due to things like nutrient shortages or other unknown reasons.

Algal Leaf Spot

Algal leaf spot and twig infection is caused by a type of algae called Cephaleuros virescens. This algae creates raised, greenish-orange spots on leaves and twigs. While usually not severe, it can weaken the tree if widespread.

Nutrient Shortages

• Little leaf: This problem makes the leaves of the pecan tree stay very small. The exact cause is sometimes unknown, but it often points to a nutrient issue.
• Mouse ear: This is caused by a lack of nickel. The leaves look small and rounded, like a mouse's ear, and the tree doesn't grow well.
• Rosette: This is a common problem caused by a zinc deficiency. The leaves become crinkled, narrow, and clustered together in a "rosette" shape. This can severely reduce nut production.

Other Disorders

• Shuck decline: This is when the outer husk (shuck) of the pecan nut doesn't develop properly or starts to rot. The cause is often unknown.
• Stem end blight: This problem affects the stem end of the nut, causing it to blacken and decay. The exact cause is also often unknown.