A short presentation on Powdery mildew of apple Presented to: Mr. Rajan Poudel and Ms. Anju Pandey

1. Powdery Mildew of Apple

2. Introduction
• Necrotic disease
• caused by Podosphaera leucotricha in Malus spp.
and Pyrus spp.
• Commonly affects upper side of leaves
• Also affects undersides of leaves, young shoots,
stems buds, flowers and young fruit

3. Introduction
• Obligate parasites
• Grows superficially and feeds through Haustoria from
epidermal cells
• Seldom kills their hosts but utilize their nutrients,
reduce photosynthesis, increase respiration and
transpiration, impair growth, reduce yield by 20-40%

4. Symptoms
• Symptoms generally appear clearly in
Apple leaves and fruits
• Other symptoms are shown by shoots
and blossoms
• Name implies the typical disease
symptom shown by this fungi

5. Symptoms: Apple shoots
• Spring: fungus colonizes young, green
tissue as it emerges k/a “Flag Shoots”
• Flag Shoots show silver-gray appearance
• Defoliation, stunted growth and die-back
• Attacked by secondary pathogens
• By mid-summer: Mycelium darkens, forms
brown ascocarps

6. Symptoms:Apple Blossoms
• Silver-gray flower buds
• Open 5-8 days later than healthy ones
• Petals: distorted, pale yellow or light
green
• Shrivel and fail to produce fruit
• Secondary infections overwinter until
the following spring

8. Symptoms: Apple Leaves and Fruits
• Secondary infections occur when
windborne spores land on young leaves
as they expand
• White felt-like patches due to the
mycelium
• Secondary infections are first observed
in lower leaf surface and then on upper
leaf surface as chlorotic spots

10. Symptoms: Apple Leaves and Fruits
• Leaves along margin curled, crinkled or
folded longitudinally
• As disease progresses, affected tissues
develop the powdery, silver-gray
appearance
• Infected fruits cause netlike russetting
and discoloration as fruit matures
• Distorted and Dwarfed

12. Disease cycle
• Conidia germinate to form hyphal
outgrowths
• Hyphal outgrowths> Appressorium>
Infection peg> Haustorium
• Continues
• Tight cluster
• Secondary infection of blossom receptable
occurs from 3 weeks before to 3 weeks
after the bloom

13. Disease Cycle
• Overwintering takes place in dormant
flower and shoot buds
• Spring- buds break dormancy and the
fungal growth is resumed
• k/a primary infections
• Asexual conidia are produced on
conidiophores and dispersed by wind
• Germinates at RH (>70%) and temperature
between 10 and 25 degree celsius

15. Management Practices
• Resistant varieties: Fuji, Delicious
• Cultural Practices:
– Removal of primary inoculum sources
– Whitened terminal shoots
• Chemical control:
– Foliar fungicide applications
– At 7 to 10 days interval from the tight-
cluster stage until terminal shoot
growth ends