🍎 Glomerella Leaf Spot (GLS) of Apple

 

✅ Causal Organism

• Teleomorph: Glomerella cingulata
• Anamorph: Colletotrichum gloeosporioides

This fungus also causes bitter rot of apple, making it a serious dual threat.

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🔍 Diagnostic Symptoms

1. Leaf Symptoms

• Small, circular to irregular brown spots with purple to dark borders.
• Spots often coalesce, leading to large dead patches.
• Often surrounded by a chlorotic (yellow) halo.
• Premature defoliation is common, especially in hot and humid weather.
  
  

  

  

  
  

  

  
  

2. Fruit Symptoms (when present)

• Small, sunken lesions similar to bitter rot.
• Lesions may ooze a pinkish spore mass in humid conditions.

3. Shoot Symptoms

• Occasional lesions on young shoots, but less common.

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🌱 Overwintering

• The pathogen overwinters as:
• Dormant mycelium or fruiting bodies (acervuli) in infected leaves, twigs, and mummified fruits.
• Can persist in fallen leaves and twig cankers on the orchard floor or tree.
• In spring, conidia and ascospores are spread by rain splash and wind to infect new tissues.

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🛡️ Disease Management Strategies

🔁 Integrated Management Approach

1. Cultural Practices

• Sanitation:
• Remove and destroy fallen infected leaves and pruned twigs.
• Remove mummified fruits post-harvest.
• Pruning:
• Open the tree canopy to improve air circulation and sunlight penetration.
• Prune out infected shoots.
• Orchard Floor Management:
• Mow or mulch to speed up leaf litter decomposition.

2. Chemical Control

• Fungicides: Apply protective sprays especially during pre- and post-bloom and summer rains:
• Captan
• Mancozeb
• Ziram
• Thiophanate-methyl
• Strobilurins (like azoxystrobin)
• Follow preventive spray programs based on weather forecasts and past disease history.

3. Resistant Varieties

• Some cultivars like ‘Golden Delicious’, ‘Gala’, and ‘Fuji’ are more susceptible.
• Use of less susceptible cultivars where GLS is a major issue may reduce disease pressure.

4. Post-Harvest

• Proper handling and storage conditions to avoid fruit rot caused by the same pathogen.

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⚠️ Note

• GLS is easily confused with other foliar diseases like Alternaria blotch or frog-eye leaf spot, so accurate diagnosis is key—often confirmed via lab identification or microscopic examination.
• For detailed explanation about symptomatology please refer to NC State university extension Apple Pathology Fact Sheet

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🍎🌿 Managing Marssonina Blotch in June: A Guide for Apple Growers in Himachal Pradesh

 

As summer 🌞 ripens across the lush apple orchards of Himachal Pradesh 🍏, farmers are once again faced with a persistent seasonal challenge — Marssonina blotch. This fungal disease caused by Marssonina coronaria thrives in warm, humid June weather 🌧️, quietly threatening your apple crop.

If you're a grower determined to protect your orchard this season, here’s your ready guide to managing Marssonina and Alternaria — with practical tips and updated spray advice 👇

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🗓️ Why June Matters for Marssonina Control

By June, apple trees are in full foliage 🌳, creating dense canopies that trap humidity — perfect conditions for fungal growth. Marssonina symptoms start as tiny dark leaf spots ⚫ that spread fast and cause premature defoliation, weakening the trees and reducing yield.

✅ Timely action now will save your crop later.

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🧹 Orchard Hygiene Comes First

Before spraying, start with simple, effective orchard practices:

🧺 Remove fallen leaves and pruned twigs
✂️ Prune trees to improve air circulation
🌿 Clear weeds and grass on the orchard floor to reduce humidity

👉 These steps help break the disease cycle and improve spray effectiveness.

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🧪 Fungicide Spray Schedule – June 2025

A strategic spray plan can keep Marssonina at bay. Here's what's recommended this June:

📅 Early June (1st Week)

💧 Tebconazole 6.7% + Captan 32% @ 200g/200L or Metiram 55% + Pyraclostrobin 5% WG 200g/ 200L Controls both Alternaria & Marssonina

💦 Ensure full leaf coverage but not drip off situation, especially under leaves

📅 Mid-June (3rd Week)

🌱 Fluxapyroxad 250g/l + Pyraclostrobin 250g/l 500SC @ 50 ml/ 200L or 🌾 Hexaconazole4% + Zineb 68% WP @ 500g/200L

✅Reliable, broad-spectrum protection against premature leaf fall/ Alternaria leaf
💡 Choose based on availability and rotation plans

☔ Post-Rain Spray

🌧️ If it rains heavily, repeat spray within 7–10 days
🕒 Rain accelerates spore spread and washes off fungicide

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🔄 Fungicide Resistance Tips

Keep your sprays effective for the long run:

🔁 Rotate between fungicide groups
🧴 Use sticker-spreaders during rainy weather
📆 Stick to the schedule — even one missed spray can cost you

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📲 Stay Connected with Advisory Alerts

🗣️ Dr YS Parmar University of Horticulture and Forestry, Nauni, Himachal Pradesh Horticulture Department and local KVKs provide real-time spray and weather alerts 📢.

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✅ To Sum It Up…

🎯 June is the month to act decisively against Marssonina blotch.
With a blend of good orchard hygiene 🧹, timely sprays 💧, and regular monitoring 🔍, your apple orchard will stay healthy and productive this season.

Got questions or want a printable version of spray schedule? 📄 Drop a comment below or contact your local horticulture office!

Wishing you a disease-free, bountiful apple season! 🍎🌳

Natural Disease Control: Using Trichoderma atroviride and Biofungicides in Apple Orchards

 

Managing diseases in apple orchards doesn't have to mean heavy chemical use. With increasing pressure for sustainable and organic practices, Trichoderma atroviride is gaining popularity as a natural fungicide for apple trees. Alongside other biofungicides for apple trees, it offers an effective and eco-friendly solution to protect your orchard.

In this guide, learn how to apply Trichoderma atroviride, when to use it, and how it fits into a biological control strategy for apple orchard disease management.

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🍏 Why Use Trichoderma atroviride in Apple Orchards?

Trichoderma atroviride is a beneficial soil fungus used for apple tree root rot treatment, collar rot control, and overall disease suppression. Here's why it's powerful:

• Mycoparasitism: It attacks and kills harmful pathogens like Phytophthora and Botrytis.
• Nutrient competition: It outcompetes pathogens in the root zone.
• Boosts immunity: Triggers the apple tree’s natural defenses.
• Improves soil health: Supports a healthy, balanced microbiome.

By applying Trichoderma atroviride in apple orchards, growers can reduce synthetic fungicide use and promote healthier trees naturally.

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🛠️ How to Apply Trichoderma atroviride in Apple Orchards

✅ When to Apply Trichoderma

To maximize effectiveness, apply during key orchard stages:

• Pre-planting – Condition the soil for planting
• At planting – Coat roots for early colonization
• Spring – Use a Trichoderma foliar spray on apple trees to prevent fungal outbreaks
• Post-pruning – Treat wounds to prevent cankers
• Autumn – Suppress pathogens before winter

📍 Where and How to Use Trichoderma

• Soil Drench or Root Dip – Apply to the root zone to prevent apple tree root diseases
• Trunk Application – Use as a wound dressing post-pruning
• Foliar Spray – Some formulations allow Trichoderma spray on apple leaves for leaf disease suppression

💡 Use non-chlorinated water, avoid mixing with incompatible chemicals, and reapply every 4–6 weeks during high-risk periods.

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🚫 Compatibility Tips and Cautions

To ensure the beneficial fungi thrive:

Compatible with:

• Organic fertilizers
• Compost teas
• Microbial inoculants like Bacillus subtilis

Avoid mixing with:

• Copper-based fungicides
• Chlorinated or high-pH water
• Broad-spectrum disinfectants

🔁 After using chemical fungicides, wait 5–7 days before applying T. atroviride.

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🌿 Best Biofungicides for Apple Orchard Disease Control

Rotating or combining biologicals can enhance performance and reduce resistance risks. Here are leading options:

Biofungicide	Target Disease	Application
Trichoderma atroviride	Root rot, collar rot, cankers	Soil, wounds, foliar (if labeled)
Bacillus subtilis	Botrytis, Alternaria	Foliar spray
Pseudomonas fluorescens	Soilborne pathogens	Root zone drench
Ampelomyces quisqualis	Powdery mildew	Preventative foliar spray

Use these biofungicides for a sustainable apple orchard management strategy.

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🌾 Integrating Biofungicides with Orchard IPM

Here’s how to combine biological control in apple farming with integrated practices:

• Scout regularly for disease pressure
• Combine Trichoderma with pruning, sanitation, and tree spacing
• Rotate different modes of action to avoid resistance
• Document outcomes to refine future strategies

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✅ Storage, Certification & Organic Use

• Ensure biofungicides are registered for use on apple trees in your region
• Store in cool, dry conditions—heat can destroy fungal spores
• Choose OMRI-listed or organic-certified Trichoderma products for organic systems

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📌 Final Thoughts

The use of Trichoderma atroviride and other biofungicides in apple orchards is not just a trend—it’s a smart, sustainable step toward healthier trees and better yields. Whether you’re managing root rot, cankers, or foliar diseases, these natural tools offer strong protection without harming the environment.

By shifting to biological fungicides, apple growers can reduce chemical inputs, improve soil health, and position their orchards for long-term success.

Integrated Disease Management & Soil Health Tips for White Root Rot in Apple Orchards

In my previous post we have talked about role of resistant rootstocks in the management of white root rot. While resistant rootstocks provide a vital first line of defense, white root rot (Dematophora necatrix) is notoriously persistent. That’s why a broader Integrated Disease Management (IDM) approach, combined with healthy soil practices, is essential for long-term orchard success.

Here’s how to level up your white root rot management strategy:

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🔄 1. Use an Integrated Disease Management (IDM) Approach

IDM combines cultural, biological, and mechanical methods to minimize disease spread and protect tree health. Focus on the following:

• 🧹 Sanitation: Remove and destroy infected roots and plant debris during replanting or pruning.

• 🧼 Disinfection: Clean tools, boots, and machinery to avoid spreading fungal spores between orchards.

• 🌱 Rootstock Selection: Choose resistant varieties like G.935 or CG.6210 when replanting or grafting.

• 📍 Site Selection: Avoid planting in previously infected soils or low-lying areas with poor drainage.

• 🔍 Regular Monitoring: Scout trees for symptoms such as leaf bronzing, shoot dieback, and root decay early.

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🌱 2. Boost Soil Health to Suppress White Root Rot

A biologically active, well-structured soil environment can naturally suppress fungal pathogens. Here’s how to enhance soil health:

• 🌊 Improve Drainage: Use raised beds or install subsurface drainage to reduce excess moisture where the fungus thrives.

• 🍂 Add Organic Matter: Apply compost, vermicompost, or well-rotted manure to support beneficial soil microbes.

• ☀️ Soil Solarization: During summer, cover moist soil with clear plastic for 4–6 weeks to kill pathogens using solar heat.

• 🌾 Biofumigation: Grow cover crops like mustard or radish, then till them under to release natural antifungal compounds.

• 🦠 Introduce Beneficial Microbes: Use Trichoderma spp. or mycorrhizal fungi as soil amendments to improve microbial competition and root protection.

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🚜 3. Smart Replanting Strategies in Infected Sites

If you're replanting in an orchard affected by white root rot, here are some essential precautions:

• ⏳ Rest Period: Leave the land fallow or plant non-host crops for 1–2 years to reduce inoculum load.

• 🌳 Resistant Rootstocks: Use only rootstocks with proven tolerance or resistance.

• 🔄 Graft on Wild Types: Consider grafting scion varieties onto wild-type or hybrid rootstocks that show field-level resistance.

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✅ Bonus Tip: Keep a Field Log

Document which rootstocks are planted where, record disease symptoms and management steps, and track the performance of soil health practices. This information is invaluable for future planning and adapting strategies as needed.

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Coming Soon:

🧪 A guide to using Trichoderma atroviride and other biofungicides in apple orchards — stay tuned!

Fighting White Root Rot in Apple Trees: The Power of Resistant Rootstocks

In my previous post I discussed about Geneva Series Rootstocks. Here we are continuing the importance of rootstocks in the management and production of the apples.   

Apple trees are iconic — not just for their fruit, but for their role in orchards around the world. But behind the scenes, many growers face a stubborn enemy lurking underground: white root rot, caused by the soilborne fungus Dematophora necatrix.

This disease is no joke. It thrives in acidic, poorly drained soils and attacks the roots of apple trees, cutting off their lifeline — water and nutrients. Left unchecked, it can wipe out trees and devastate entire orchards.

So what’s the solution? One of the most promising long-term strategies is using resistant rootstocks. Let’s dig into why that matters.

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What Makes White Root Rot So Dangerous?

The fungus behind white root rot is a survivor. It can live in the soil for years — even if no apple trees are around. In fact, it’s been known to infect over 170 plant species, including other fruit trees and woody plants.

Once it gets into an orchard, it infects the roots and slowly takes over. You'll see signs like:

• Leaves turning bronze

• Shoots dying back

• Smaller fruits

• Entire trees collapsing

And here's the worst part: traditional control methods like chemical treatments or rotating crops don’t work well because the fungus is so persistent and adaptable.

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Why Resistant Rootstocks Are a Game-Changer

Rootstocks are basically the foundation of the apple tree — the part that grows underground and supports the rest of the plant. By choosing the right rootstock, growers can improve everything from tree size to disease resistance.

Here’s why white root rot-resistant rootstocks are such a big deal:

• 🌳 They help trees survive and stay productive, even in infected soils.

• 🐞 They reduce the need for chemical treatments, making farming more eco-friendly.

• 🔄 They offer broader disease protection, especially when bred alongside other resistant traits.

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Promising Rootstocks to Watch

Researchers and breeders have been hard at work developing and testing rootstocks that can handle white root rot. Here are a few that are showing promise:

• M.9 and M.26: Popular for creating smaller, high-yielding trees — but unfortunately, they’re susceptible to white root rot.

• G.935: Part of the Geneva series. Offers moderate resistance, plus it’s hardy and resistant to fire blight.

• CG.6210: A strong contender with broad soilborne disease tolerance and great compatibility with many apple varieties.

• Seedling rootstocks: Wild apple species and hybrids are being explored, and some show natural resistance — a promising direction for future breeding.

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Looking Ahead

White root rot isn’t going away anytime soon, but we’re not powerless. By investing in and planting resistant rootstocks, apple growers can protect their orchards, reduce chemical use, and grow healthier trees for the long haul.

Breeding efforts are still ongoing, and with continued research, the future of apple farming looks a lot more resilient.

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Got white root rot problems in your orchard? Stay tuned for our upcoming post on integrated disease management strategies and soil health tips.

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Apple Tree Diseases: Objective questions on apple

Yesterday I posted some objective questions on apple in the form of fill in the blanks. Today again I am going to post some more fill in the blanks with reasoning questions. This will complete important questions from apple fruit crop.

Fill in the blanks:

1. Unlike apple scab fungus, the spores of powdery mildew do not require _____________ for germination.
2. Black rot disease of apple is caused by                               and is also known as                         .
3. Phytophthora cactorum  survives in the soil as                                      that are resistant to drought and relatively resistant to chemical treatment.
4. Characteristic feature of white root rot is                                                that can be seen on roots during monsoon months and can be seen on soil level.
5. Young trees if infested with                                                   may die quickly with necrotic leaves still on the dead plant is a characteristic symptom.
6. Soil pH                 , soil moisture                 and Temperature                  play an important role in incidence and survival of Dematophora necatrix.
7. Crown gall of apple is caused by                                 and hairy root is caused by                       can be managed by bio-control agent                                                   strain

Descriptive questions

1. How excess nitrogen makes the plants more susceptible? What is the role of balanced nutrition in disease management?
2. Why overhead irrigation be avoided during fire blight outbreak?
3. Why control of insects with sucking type of mouth parts is important in management of fire blight of pome fruits?

You may answer the fill in the blanks in comment section. I shall be posting the answers in comment section tomorrow.

Apple Tree Diseases: Objective questions on apple diseases.

Yesterday I started working on objective type questions for the diseases of apple crops. In this series I am going to  post fill in the blanks. Here are few fill in the blanks for apple diseases.

Fill in the blanks

1. Apple scab is caused by _______________ is telomorph, whereas, anamorph of the fungus is ______________.
2. Apple scab disease perinnates in ____________and primary infection is caused by ______________.
3. Leaf __________period and _____________plays important role in primary infection of apple scab.
4. Secondary source of inoculum for scab development is __________.
5. Application of _________to leaf litter during fall (when more than 80% leaves have fallen) hasten decomposition of leaves due to microbial action and reduces primary inoculum.
6. In case of fire blight of apple, tips of young infected shoots wilt, forming a very typical ________________symptom.
7. The fire blight bacteria ____________in bark tissues along the edges of cankers caused by infections during previous years.
8. The Erwinina amylovora penetrate the tree through __________or ______________.
9. Secondary infection of Erwinina amylovora arises from _______of fresh infections.
10. Podosphaera leucotricha overwinters in the ____________that had been infected in the preceding growing season.

You may answer these questions in comment section. I shall be answering these in comment section tomorrow. 

Apple Tree Diseases: Question Bank for Apple Diseases

During the period of lockdown, I thought to help my students in preparation for their exams. Today I am starting with few questions on apple diseases, which may come handy for your exams in near future. Tomorrow I shall be posting some more questions.

MCQ. 

Q 1 The disease which had endangered the very existence of delicious apples.

a. Powdery mildew	c. Fruit spots
b. Apple scab	d. Root rot

Q 2 The breeding of scab resistant varieties of apple was undertaken.

a. IARI	c. RFRS – Mashobra
b. ICAR	d. RFRS – Bikaner

Q 3 The root rot of apple is caused by.

a. Phytophthora cactorum	c. Corticium salmonicolor
b. Podospharea leucotricha	d. Botryosphaeria obtusa

Q 4 Silvering of foliage appears soon after petal fall is the typical symptoms of

a. Nail head canker	c. Pink disease
b. Leaf canker	d. Fruit spots

Q 5 Hairy root is due to.

a. Agrobacterium tumefaciens	c. Podospharea leucotricha
b. Dematophora necatrix	d. Corticium salmonicolor

State True /False

Q 6 The Primary Source of Inoculum  for apple scab is zoospores of pseudothecium.

Q 7 The apple rust is a heterocious & also monocyclic disease.

Q 8 Apple crown rot. Root rot, Collar rot are the complete loss disease caused by a single organism Dematophora necatrix.

Q 9 Apple Dapple /Apple scar skin is a viroid disease.

Q 10 The two crab apples Malus floribunda & Malus toringoides are have resistance against the root rot.

Q 11 Bitter rot, Sour rot, Brown rot are not post harvest diseases.

You may answer these questions in comment box. I shall be posting the answers soon in comment section

Apple Tree Diseases: Monitored Sprays for Apple Scab

This post is in continuation to my previous post on Apple Diseases:Holistic Management of Apple Scab. Here we are going to discuss about Monitored spray control

There are two spray strategies for controlling the diseases i.e. preventive and curative. Since this disease is a polycyclic, the spray schedule should focus on reduction of inoculum and protective covering before the infection takes place based on the predictive models developed at RHRTS Mashobra.

Monitored Spray control:           
 Among two different monitored spray strategies (curative and eradicative) as developed and tried in the orchards, the curative sprays with well timed application of Ergosterol-biosynthesis-inhibiting (EBI) fungicides even after 72 and 96 hour of the predicted infection periods is not only more effective but also economical for control the disease with three lesser sprays.

Av Temp (oC)	Minimum wetness (hr)		Scab appear (days)
	Ascospores	Conidia
17.2-23.8	9.0	5.9	9
13.8-11.0	11.0	7.5	15
10.5-8.5	15.0	9.8	17

The monitored spray programme developed for Indian conditions at Regional Horticultural Research and Training Station, Mashobra, Shimla for the control of spring and summer scab conditions is described below. This strategy is recommended to orchard areas where scab is present.

First Spray:

At green tip stage if scab during last three years was present and temperature after rains remained above 10^oC. The spray strategy to control primary scab must include high residue fungicides for better protective action for longer duration. The strong bio-efficacy of dodine, mancozeb, dithianon, and captan is established on apple parts. The residues of these fungicides are persistent, stable and re-distributive on the foliage and remain effective against primary infection up to 36 days. Hence recommended at green tip stage as first spray under monitored control program in Himachal Pradesh.

Second Spray:

Second spray at pink bud stage is recommended to give protective coverage on plant parts to control primary scab infection during the long flowering session. However, according to monitored spray strategy, this spray is considered to be optional and should be given only if first spray is not given or continuous wet conditions prevailed after the first spray. The fungicides recommended at this stage are both protective as well as curative. However, it is also observed that at high altitude locations (above 6500 ft) where primary infection generally initiates after pink bud stage the first spray at green tip stage is inappropriate. Benzimidazole and EBI fungicides having protective/ curative and broad-spectrum mode of action is recommended for such locations at pink bud stage (as first spray) to control invisible infection caused by apple scab, canker fungi, powdery mildew, core rot and leaf blotch. However, the sensitive flowering stage is avoided for any spray as might obstruct the cross-pollination process.

Criteria for sprays:

In addition to its anti-fungal properties it also help in improving fruit set and can be used safely during bloom.

Third Spray:

Third spray at petal fall stage is very essential to protect the newly emerged fruit-lets against primary scab and powdery mildew infections. Moreover, the earlier sprays given either through first spray or at pink bud stage are found ineffective all through the long flowering period of apple. The brands of benzimidazole and EBI are recommended at this stage also having both protective curative and anti-sporulant actions. This group of fungicides is effective to other summer diseases as well and also acts as anti-senescent and increased fruit set.

Fruit Development Spray:

At fruit development stage the actual monitored spray strategy implies where curative fungicide sprays are recommended after the infection period instead of routine sprays. There are three options of sprays and type of fungicides use according to the prevailing weather and scab conditions in the orchards.

Most effective option of curative (EBI) fungicides is to kill the fungus in host tissues after the infection has occurred. However, the fruit development sprays can be extended for longer duration or discontinue in case there is no visible scab on leaves and fruits out of primary infection. This can also be ascertained by the overall scab records in the last three years and no primary symptoms have appeared till date in the current period.

Dormant spray:

Dormant sprays of 5 per cent urea a foliar nitrogenous fertilizer at leaves shedding stage and followed by a spray of Bordeaux mixture (1%) are most effective IDM strategy used to eradicate the most overwintering pathogen/diseases on apples.

In coming posts I shall be discussing about the cankers.