Pest & Disease Powdery mildew

Powdery mildew

Podosphaera leucotricha

What is Powdery Mildew (Podosphaera leucotricha)?

Powdery mildew (Podosphaera leucotricha) is a fungal disease that affects a variety of plants, such as apples, almonds, pears, quince, peach, and photinia. It is found worldwide in apple production regions. This disease can impact leaves, buds, shoots, blossoms, and fruit. Typical symptoms include whitish patches on the lower leaf surface, yellow spots on the upper surface, and a powdery appearance due to white spores. Leaves may exhibit curling and dropping, while buds become more vulnerable to winter damage. Infected fruit may develop a netlike russeting.

How does Powdery Mildew (Podosphaera leucotricha) occur?

Powdery mildew reproduces through a combination of asexual and sexual methods. It produces asexual spores called conidia, which spread through wind or insects, causing new infections. Under specific conditions, it forms sexual fruiting bodies called chasmothecia, which produce sexual spores called ascospores. These ascospores can survive tough conditions and infect plants in the following seasons. The ability to reproduce both ways helps powdery mildew survive, spread, and adapt as a plant disease.

Symptoms

1 - Effects on plants

Powdery mildew weakens plants by interfering with their photosynthesis, resulting in reduced vigor and growth. Moreover, infected plants may experience decreased fruit or flower production, leading to lower overall yields.

2 - Effects on soil

Infected leaves that decompose can disrupt the natural process of nutrient cycling in the soil. It can also affect the composition and function of soil microorganisms, potentially altering soil ecology.

3 - Effects on the Environment

Severe powdery mildew outbreaks can harm plant diversity, impacting ecosystems where susceptible plants are prevalent.

Solutions

6 - Cultural Control

• Pruning and sanitation: Pruning helps reduce inoculum by removing infected plant parts, but it can be labor-intensive for larger operations. • Orchard maintenance: Regular maintenance, including opening the tree canopy, improves fungicide deposition and reduces humidity, hindering pathogen development.

7 - Chemical Management

• Timely fungicide applications effectively control powdery mildew. • Elemental sulfur is commonly used for management. • Inorganic potassium carbonates and kaolin-based particle film are used in organic production. • Resistance management strategies include rotating fungicide modes of action. • Anilinopyrimidines, once commonly used, are now less favored. • Surfactant treatments show some reduction in infections but may delay bud break and flowering. • Fungicide-surfactant mix applications are more effective with reduced phytotoxicity.

8 - Biological Control

• Plant oil extracts, like sunflower, olive, and canola oils, can control powdery mildew symptoms. • Biocontrol organisms (e.g., Ampelomyces mycoparasites, Bacillus species) show varying success. • Research is ongoing to identify effective biocontrol agents and naturally derived antimicrobial compounds.

Susceptible Species

Peaches And Cream Japanese Maple

Strawberry Tree

Common Paw Paw

Akane Apple

Ambrosia Apple

Belle de Boskoop Apple

Braeburn Apple

Candied Apple Flowering Crab

Chehalis Apple

Cortland Apple

Cox's Orange Pippin Apple

Dolgo Apple

Donald Wyman Flowering Crab

Elstar Apple

Gala Apple

Golden Delicious Apple

Golden Russet Apple

Granny Smith Apple

Gravenstein Apple

Honeycrisp Apple

Jonagold Apple

Jonathan Apple

Liberty Apple

Lodi Apple

Louisa Flowering Crab

Macintosh Apple

Melrose Apple

Norland Apple

Pink Lady Apple

Red Delicious Apple

Red Jewel Flowering Crab

Scarlet Pippin Apple

Sentinel Flowering Crab

Snowdrift Flowering Crab

Spartan Apple

Summerland Apple

Wealthy Apple

Yellow Transparent Apple

Zestar Apple

pineapple guava

apple serviceberry

apple serviceberry

pineapple

pineapple

variegated pineapple

custard apple

strawberry tree

willow bell

willow bell

peach-leaved bellflower

willow bell

willow bell

willow bell

Japanese quince

Japanese quince

flowering quince

flowering quince

flowering quince

flowering quince

flowering quince

flowering quince

star apple

quince

pineapple broom

pricklyburr

argyle-apple

pineapple lily

pineapple lily

pineapple lily

pineapple lily

flowering crabapple

flowering crabapple

flowering crabapple

crabapple

apple

Siberian crabapple

flowering crabapple

flowering crabapple

crabapple

flowering crabapple

crabapple

apple

Japanese crabapple

crabapple

flowering crabapple

flowering crabapple

flowering crabapple

apple

dwarf apple

columnar apple

columnar apple

dwarf apple

Sargent crabapple

Sargent crabapple

flowering crabapple

crabapple

flowering crabapple

flowering crabapple

flowering crabapple

redbud crabapple

apple mint

may-apple

may-apple

may-apple

David's peach

dwarf peach

peach

ornamental peach

dwarf peach

peach

peach

dwarf nectarine

dwarf nectarine

dwarf nectarine

Chinese-quince

dappled willow

pineapple sage

pineapple sage

Malaysian apple

atlas broom

Royal Raindrops crabapple

European crabapple

pineapple weed

Bael

Cashew Nut

Pineapple

Smooth-barked apple

Pond Apple

Mountain Soursop

Custard Apple (Chirimoya - Cuba)

Golden Sugar Apple

Sugar Apple

Albino Berry

Pineapple Broom

Pawpaw

Peach Palm

Swallow-Wort

Cocky apple

Seven-year Apple

Dwarf Apple Blossom Tree

Apple Blossom Tree

Apple Blossom Tree

Pink Shower Tree

Palmilla

Night Blooming Cereus

Flowering quince

Caimito

Copey

Quince

Desert Thorn Apple

Thorn Apple

Thorn Apple

Jimsonweed

Pineapple Orchid

Elephant Apple

Katmon

Velvet Apple

Gold Apple

Kei Apple

Argyle Apple

Pineapple Lily

Pineapple Lily

Pineapple Lily

Feijoa

Seven Year Apple

Hibiscus Jane Cowel Double peach

Wild peach

Pineapple Zamia

Sunsapote

Wood Apple

Osage Orange

Apple

Low Chill Apple

Mammee Apple

Pomme Jacquot

Balsam Apple

Bitter Melon

Mouse's Pineapple

Mussaenda Queen Sirikit

Sweet Calabash

Bell Apple

Apple Leaf

Cocky Apple

Monkey Apple

Cinnamon Apple

Broadleaved Lucuma

Nectarine

Peach

Pineapple Sage

African Peach

Pineapple Cactus

Cockroach berry

Kangaroo Apple

Tropical Soda Apple

Cork Tree

Gedabu

Water Cherry

Sea Apple

Rose apple

Malay Apple

Wild Rose Apple

Wax jamboo

Red Bush Apple

Adam's Apple

Eve's Apple

Wild Custard Apple

Elephant Apple

Apple

Water Apple

White Apple

Pineapple Guava