Tag: fungal diseases

• Potato is susceptible to various fungal and viral diseases.
• Major diseases include early blight, late blight, black scurf, leaf roll, and mosaic viruses.
• Effective management requires understanding pathogen biology and disease cycles.

• Small, dark lesions with concentric rings (bull’s eye) on older leaves.
• Yellowing tissue around spots; severe cases cause foliage death.
• Stem lesions may girdle plants near soil line.

Etiology:

• Septate, branched, light brown mycelium; conidia borne in chains, obclavate, muriform.

Disease Cycle:

• Primary infection from mycelium/conidia in plant debris.
• Secondary spread by wind, water, or rain splash.

Management:

• Use disease-free seed and crop rotation.
• Remove and destroy infected debris.
• Fungicide sprays: Mancozeb 0.25%, Chlorothalonil 0.2%, or Zineb 0.25% at intervals.

• Water-soaked, dark lesions on lower leaves, expanding rapidly in cool, moist weather.
• Lesions not limited by veins; entire leaves may die quickly.
• Tubers show irregular, sunken, brown to purplish areas with granular rot beneath skin.

Etiology:

• Coenocytic, hyaline, branched mycelium; sporangia are oval/pear-shaped, germinate by zoospores.

Disease Cycle:

• Primary infection from infected tubers and soil.
• Airborne sporangia cause secondary spread.

Management:

• Protective fungicide sprays (Mancozeb/Zineb 0.2%).
• Use resistant varieties (e.g., Kufri Naveen, Kufri Jeevan).
• Destroy foliage before harvest; avoid tuber injury during harvest.

• Necrosis at sprout tips, sunken lesions on stolons, roots, stems.
• Black sclerotia (scurf) on tuber surface.
• Stunted plants, purplish leaves, deformed tubers.

Etiology:

• Basidiomycete fungus; produces sclerotia, rarely basidiospores.
• Mycelium is septate, branched; sclerotia are dark brown to black, irregular.

Disease Cycle:

• Primary infection from sclerotia in soil.
• Seedlings from infected soil spread disease.

Management:

• Plant only disease-free seed tubers.
• Seed treatment with fungicides (e.g., mercuric chloride; safer alternatives preferred).
• Crop rotation and shallow planting reduce severity.

• Upward rolling of young leaves; leaves become dry, thick, and brittle.
• Plants are stunted, erect, light green; tubers reduced in size and number.
• Net necrosis may develop inside tubers.

Transmission:

• Spread by aphids (Myzus persicae, Aphis gossypii) and infected tubers.

Management:

• Use disease-free, certified seed tubers.
• Rogue and bury diseased plants.
• Control aphids with insecticides (e.g., Phorate 10G, 10 kg/ha).

• Light yellow mottling, slight crinkling, interveinal necrosis, mild stunting.

Severe Mosaic (Potato virus Y – PVY):
Symptoms:

• Chlorotic and necrotic streaks, leaf drop, interveinal and stem necrosis, stunting, leaf rugosity.

Rugose/Common Mosaic (PVX & PVY):
Symptoms:

• Black streaks on veins/stems, shriveled and mottled leaves, dwarfing, reduced tuber size.

Transmission:

• PVX: Mechanical (sap), seed, tools, contact.
• PVY: Aphids (Myzus persicae, Aphis gossypii), infected tubers.

Management:

• Use disease-free, certified seed tubers.
• Grow resistant varieties (e.g., Chippewa, Irish Cobbler).
• Rogue diseased plants; control aphids (Phorate 10G, 10 kg/ha).
• Early harvesting and hygiene reduce spread.

• Use certified, disease-free seed tubers for all plantings.
• Practice crop rotation and field sanitation to reduce inoculum.
• Apply recommended fungicides and insecticides judiciously.
• Grow resistant varieties where available.
• Monitor fields regularly for early detection and management.

• Botanical name: Camellia sinensis
• Chromosome number: 2n = 30
• Origin: China
• Tea is susceptible to various fungal, algal, and oomycete diseases affecting yield and quality.
• Effective disease management is crucial for sustainable tea cultivation.

• Circular, raised, purple to reddish-brown lesions on leaves.
• Older spots become greenish-gray, resembling lichen.
• Most lesions develop on upper leaf surface; rarely harmful to plant vigor.

Disease Cycle:

• Alga produces rust-colored spore-like bodies on leaf spots.
• Dispersed by wind or rain; favored by high humidity and poor drainage.

Management:

• Avoid plant stress and poorly drained sites.
• Promote air circulation; prune and destroy infected parts.
• Apply Bordeaux mixture; improve soil nutrition (NPK).

• Small, oval, pale yellow-green spots on young leaves.
• Spots enlarge, turn brown/gray with concentric rings and black dots.
• Leads to defoliation; affects leaves of all ages.

Disease Cycle:

• Fungal spores in black dots on lesions.
• Spread by rain splash; infect new leaves under wet conditions.

Management:

• Avoid plant stress; ensure adequate spacing for air flow.
• Spray Copper Oxychloride or Bordeaux mixture (0.1%) in winter and summer.

• Pinhole-sized spots on young leaves (<1 month old).
• Spots enlarge, become transparent, then light brown.
• Blister-like symptoms with water-soaked zones; blisters turn white and velvety, then brown.
• Young stems may bend, break, or die.

Disease Cycle:

• Continuous cycle in wet conditions; spores dispersed by wind.
• Direct penetration of leaf tissue; symptoms in 10 days.

Management:

• Prune and destroy affected leaves and shoots.
• Spray Bordeaux mixture, Copper Oxychloride (0.1%), or triazole fungicides (e.g., hexaconazole).
• Apply fungicides at 5-day intervals during rainy season.

• Black, hair-like fungal threads on upper branches and twigs.
• Rapid leaf drop due to volatile substances produced by fungus.

Disease Cycle:

• Spread via extension of hair-like threads from infected to healthy twigs.

Management:

• Remove and destroy crop debris.
• Prune out infected or dead branches.

• Small, brown, irregular spots on flower petals.
• Whole flower turns brown and drops prematurely.

Disease Cycle:

• Emerges in early spring during high moisture periods.

Management:

• Remove infected flowers and crop debris.
• Apply soil drenches with suitable fungicides.

• Browning and drooping of leaves; shoots dry and die.
• Cankers form on branches; tip dieback.

Disease Cycle:

• Spores produced on dead branches; spread by rain splash.
• Entry through wounds; survives on pruned branches.

Management:

• Plant in well-drained, acidic soils.
• Remove diseased twigs below cankered areas; disinfect tools.
• Apply protective fungicides during wet weather.

• Originates from dead leaves above soil; spreads to roots.
• Star-like mycelium under bark; mycelium surrounds stem base.
• Swollen ring of tissue above dead patch.

Management:

• Remove and destroy infected plants.
• Practice clean cultivation; remove fallen leaves.
• Dig trenches around infected bushes to expose soil to sunlight.

• Sudden yellowing and wilting of leaves; branch tip dieback.
• Gray blotches and sunken cankers on bark and stem.
• Cankers girdle stem; upper parts lose vigor and die.

Comments:

• Fungus enters through wounds; symptoms worsen in hot, dry weather.

Management:

• Plant in well-drained, acidic soils.
• Remove diseased twigs below cankers; disinfect tools.
• Apply protective fungicides during wet periods.

• Yellowing leaves; poor growth; wilting; discolored roots; rapid plant death.

Comments:

• Favored by poorly drained, warm soils.

Management:

• Plant in well-drained soils; avoid waterlogging.
• Apply appropriate fungicides to protect plants.

• Yellowing foliage; wilting or sudden death of plant parts.
• Withered leaves remain attached; red discoloration of roots; whitish mycelium visible.

Comments:

• Spread by mycelial strands in soil.

Management:

• Remove infected bushes and adjacent symptomatic plants.
• Remove all living/dead roots and stumps; destroy by burning.
• Treat surrounding bushes to prevent spread.

• Apply Benomyl or Copper Oxychloride (0.01%).
• Use botanical extracts (e.g., Azadirachta, A. nilagirica) at 10% concentration.
• Apply biocontrol agents (Bacillus sp., Pseudomonas sp., Trichoderma viride).

• Use Bacillus megaterium as a plant growth promoter and biocontrol agent.
• Induces systemic resistance and reduces disease incidence.

• Apply antagonistic fungi (e.g., Aspergillus niger, Trichoderma atroviride, T. citrinoviride) as foliar sprays.
• Reduces symptom severity and disease index.

• Combine cultural, chemical, and biological control methods for sustainable management.
• Use resistant varieties where available.
• Maintain field hygiene: remove debris, prune infected parts, ensure proper spacing.
• Apply fungicides judiciously to avoid resistance.
• Promote beneficial microorganisms for biocontrol.

• Papaya is susceptible to various fungal, viral, and post-harvest diseases.
• Diseases affect yield, fruit quality, and marketability.
• Effective management requires accurate diagnosis and integrated approaches.

• Powdery Mildew: Oidium indicum, Oidium caricae, Leveillula taurica
• Leaf Blight: Corynespora cassiicola
• Damping-Off: Pythium aphanidermatum, Rhizoctonia solani
• Foot Rot: Pythium aphanidermatum
• Anthracnose: Colletotrichum gloeosporioides

• Speckled, water-soaked spots on leaf underside.
• Powdery patches enlarge, covering leaves.
• Leaves become chlorotic, distorted, and fall prematurely.

Management:

• Clean cultivation and balanced fertilization (increase K, reduce N).
• Dusting sulfur (30 g/10 L water) at symptom onset.
• Spray Triadimefon (0.1%) or systemic fungicides (Bayleton, carbendazim) at intervals.

• Water-soaked patches at stem base, girdling stem.
• Tissues turn brown/black and rot; terminal leaves yellow and wilt.
• Fruits shrivel and drop; plant may topple and die.
• Roots deteriorate; bark appears dry, honeycomb-like.

Management:

• Use well-drained nursery beds; remove and destroy diseased seedlings.
• Apply Trichoderma viride (15 g/plant) with FYM at planting.
• Seed treatment with captan (4 g/kg) or chlorothalonil (2 g/kg).
• Drench stem base with COC (0.25%), metalaxyl (0.1%), or Bordeaux mixture (1.2%).

• Gray to brown spots with dark margins and yellow halo on leaves.
• Necrotic areas form as spots coalesce.
• Fruits develop light spots that enlarge, become dark brown, and may show concentric rings.
• Premature fruit drop common.

Management:

• Remove and destroy affected fruits.
• Harvest fruits at maturity.
• Spray copper oxychloride (0.3%), carbendazim (0.1%), or thiophanate-methyl (0.1%) every 15 days.
• Hot water or fungicidal wax treatment for export fruits.

• Papaya Mosaic Virus (transmitted by Aphis gossypii)
• Papaya Leaf Curl Virus (transmitted by Bemisia tabaci)
• Papaya Ring Spot Virus (PRSV; transmitted by aphids)

• Mild mosaic pattern and deformation in young leaves.
• Dark green blister-like patches on yellowish-green leaves.
• Leaf vein clearing, downward curling, and shortened petioles.

• Severe curling, crinkling, and deformation of young leaves.
• Vein clearing and thickening; twisted petioles.
• Stunted growth, reduced yield, and possible defoliation.

• Prominent mosaic and chlorosis on leaves.
• Oily streaks on petioles and trunk.
• Distorted young leaves; concentric rings and C-shaped markings on fruits.

• Use disease-free seedlings for planting.
• Rogue and destroy infected plants promptly.
• Control vectors with insecticides (monocrotophos 0.05%, dimethoate 0.2%, metasystox 0.1%).

• Macrophomina Rot: Macrophomina phaseolina
• Rhizopus Rot (Soft Rot): Rhizopus stolonifer
• Phomopsis Rot: Phomopsis caricae
• Anthracnose: Colletotrichum gloeosporioides

• Small water-soaked spots on fruit surface.
• Spots deepen, causing internal rot and sclerotia formation.
• Inner tissues turn brownish-black with dark mycelial growth.

• Irregular water-soaked lesions on injured fruits.
• Lesions covered with whitish fungal growth, turning dark brown.
• Fruit becomes watery, emits foul odor, and infection spreads rapidly.

• Initial water-soaked spots become sunken and dark brown to black.
• Spots may be surrounded by white, raised tissue.
• Infected area becomes soft and pulpy.

• Harvest fruits at proper maturity and during cool hours.
• Dipping fruits in TBZ (1000 ppm) or benomyl (20 ppm) reduces storage decay.
• Dusting fruits with benzoic acid (0.1%) in kaolin reduces rotting.

• Adopt clean cultivation and use disease-free planting material.
• Monitor and manage vectors for viral diseases.
• Apply recommended fungicides and biological agents for fungal diseases.
• Practice proper post-harvest handling to minimize losses.

• Cabbage is susceptible to several economically important fungal diseases.
• Fungal pathogens affect yield and quality.
• Early identification and management are crucial for disease control.
• Integrated approaches are recommended for sustainable management.

• Pathogen: Rhizoctonia solani.
• Symptoms: Stem constriction at base, stunted growth, seedlings may break at ground level.
• Favored by mechanical injury and wet conditions.
• Management: Use certified disease-free transplants, avoid injury, ensure good drainage.

• Pathogen: Fusarium oxysporum f. sp. conglutinans.
• Symptoms: Leaf yellowing, wilting, stunted growth, twisted stems, unilateral midrib curvature.
• Soil-borne and persists for years.
• Management: Grow resistant varieties, crop rotation, use disease-free seed.

• Pathogen: Leptosphaeria maculans (Phoma lingam).
• Symptoms: Light brown stem lesions with purplish margins, black dots (pycnidia), cankering at base.
• Seed and residue-borne.
• Management: Use disease-free seed, hot water seed treatment, crop rotation, sanitation.

• Pathogen: Alternaria brassicae, A. brassicicola.
• Symptoms: Circular brown to black spots with concentric rings and yellow halos.
• Seedborne and airborne spread.
• Management: Remove crop debris, seed treatment, crop rotation, fungicide application.

• Pathogen: Plasmodiophora brassicae (plasmodiophoromycete, not true fungus).
• Symptoms: Root galls, wilting, stunted and yellow leaves, premature bolting.
• Favored by acidic, moist soils.
• Management: Use clean seedbeds, long crop rotations, lime soil to raise pH, resistant varieties.

• Pathogens: Fusarium spp., Pythium spp., Rhizoctonia solani.
• Symptoms: Seedling collapse, wet rot at stem base, missing or wilted seedlings.
• Favored by high moisture and poor drainage.
• Management: Use sterilized soil, raised beds, good drainage, biocontrol agents.

• Pathogen: Hyaloperonospora brassicae (formerly Peronospora parasitica).
• Symptoms: Yellow patches on upper leaf surface, white fluffy growth below, leaf drop, black spots on curds.
• Favored by cool, moist conditions.
• Management: Resistant varieties, crop rotation, debris removal, avoid leaf wetting, fungicides.

• Pathogen: Erysiphe cruciferarum.
• Symptoms: White powdery growth on upper leaf surfaces, reduced vigor.
• Favored by dry, warm conditions.
• Management: Resistant varieties, fungicides, avoid excess nitrogen, reduce drought stress.

• Pathogen: Albugo candida (oomycete, not true fungus).
• Symptoms: White blisters on leaf undersides, yellow patches above, stem distortion, leaf galls.
• Favored by cool, moist weather.
• Management: Resistant varieties, crop rotation, fungicides.

• Pathogen: Mycosphaerella brassicicola.
• Symptoms: Grey leaf lesions with black dots in concentric rings, reduced growth, delayed harvest.
• Spread by seed and debris.
• Management: Hot water seed treatment, fungicides, remove infected plants and debris.

• Pathogens: Sclerotinia sclerotiorum, S. minor.
• Symptoms: Water-soaked lesions, fluffy white mycelium, black sclerotia inside stems.
• Favored by high humidity and dense canopy.
• Management: Improve air circulation, avoid injury, crop rotation, remove infected debris.

• Pathogen: Rhizoctonia solani.
• Symptoms: Tan or brown lesions on outer leaves, rapid head rot.
• Favored by wet, poorly drained soils.
• Management: Raised beds, proper fertilization, maintain plant health.

• Pathogen: Phytophthora megasperma.
• Symptoms: Leaf margin discoloration (red/purple), root and stem rot, plant wilting and death.
• Favored by poorly drained soils.
• Management: Improve drainage, crop rotation, soil treatments, fungicides.

• Use disease-free seed and resistant varieties.
• Practice crop rotation and field sanitation.
• Maintain proper drainage and avoid plant injury.
• Apply fungicides judiciously as needed.
• Monitor regularly for early detection and control.

• Pea (Pisum sativum) is susceptible to several fungal diseases.
• Major diseases include Fusarium wilt, powdery mildew, downy mildew, rust, and Ascochyta blight.
• Effective management requires understanding pathogen biology and disease epidemiology.

• Caused by Fusarium oxysporum f. sp. pisi.
• Initial symptoms: drooping, yellowing, and premature leaf drop.
• Pod formation is severely affected; collar region shows necrosis and discoloration.
• Dark brown vascular discoloration visible in stem cross-section.

• Pathogen survives in soil for long periods; infects via root hairs.
• Primary infection: soil, seed, water; secondary: conidia via rain splash.
• Favored by soil temperatures of 23–27°C and warm weather.
• Seed treatment with carbendazim (2 g/kg) and soil drenching with copper oxychloride (0.25%) recommended.

• Caused by Erysiphe pisi.
• Appears as white powdery spots on leaves, stems, and pods.
• Severely infected leaves become chlorotic, distorted, and may fall.
• Pods may be small and malformed.

• Spread by airborne spores; thrives in warm (15–25°C), humid (>70%) conditions.
• Cultural control: use resistant varieties, destroy infected stubble, avoid adjacent sowing to previous pea fields.
• Chemical control: sprays of benomyl, carbendazim, sulphur, or triadimefon as per recommended doses and intervals.

• Caused by Peronospora viciae.
• Grayish-white mold on lower leaf surface; yellowish area on upper side.
• Infected leaves turn yellow, die; stems may be stunted and distorted.
• Brown blotches and mold may develop on pods.

• Primary infection: soil, seed, water; secondary: sporangia via rain splash or wind.
• Favored by high humidity and low temperatures (5–15°C).
• Remove and burn diseased plants promptly to reduce inoculum.

• Caused by Uromyces pisi.
• Initial symptoms: leaf flecking, progressing to reddish-brown pustules.
• Pustules merge, burst, and release brown spores; severe cases cause plant drying and yield loss.

• Survives on infected plant debris and alternate hosts (e.g., Euphorbia).
• Favored by frequent precipitation, dew, and temperatures of 20–25°C.
• Cultural control: destroy debris, crop rotation with non-legumes, mixed cropping.
• Chemical control: sulphur or triadimefon sprays as per recommendations.

• Caused by Ascochyta pisi, A. pinodes, and A. pinodella.
• Symptoms: purplish-brown flecks on lower leaves, stems, tendrils; lesions enlarge and coalesce.
• Severe infection causes foot rot (purplish-black lesions at soil line), lodging, and pod lesions.
• Pod infection leads to small, discolored, or shrunken seeds.

• Ascospores spread by wind; conidia by rain splash.
• Primary infection from diseased seed or soil debris.
• Favored by warm, humid conditions (15–25°C).
• Use resistant varieties (e.g., B-90, CDC Frontier, CDC Luna), seed treatment with thiabendazole, and crop rotation.

• Combine cultural, chemical, and genetic resistance strategies for effective control.
• Use certified disease-free seed and resistant varieties.
• Practice crop rotation and field sanitation.
• Apply fungicides judiciously based on disease monitoring and recommendations.

• Cucurbits include cucumber, melon, watermelon, pumpkin, squash, and gourds.
• Major diseases: Downy mildew, Powdery mildew, Fusarium wilt, Angular leaf spot, Cucumber mosaic, and Tospovirus.
• Diseases caused by fungi, bacteria, and viruses.
• Effective management requires accurate diagnosis and integrated control strategies.

• Pathogen: Pseudoperonospora cubensis (oomycete fungus).
• Hosts: All major cucurbits.
• Symptoms: Small yellow, water-soaked lesions on upper leaf surface; lesions turn brown and necrotic.
• Severe infection causes leaf curling, death, and reduced fruit quality.

• Survives on collateral hosts and plant debris.
• Spread by wind-borne sporangia and rain splash.
• Management: Remove weeds, avoid overhead irrigation, use resistant varieties.
• Fungicide sprays: Metalaxyl, chlorothalonil, or zineb at recommended intervals.

• Pathogens: Erysiphe cichoracearum and Sphaerotheca fuliginea.
• Symptoms: White, powdery mycelium on both leaf surfaces, stems, and petioles.
• Leads to leaf yellowing, drying, premature defoliation, and fruit deformation.

• Overwinters as cleistothecia or on collateral hosts.
• Spread by wind-borne conidia.
• Management: Use resistant varieties, ensure good air circulation, apply fungicides (e.g., Calixin, Karathane).

• Pathogen: Fusarium oxysporum f.sp. niveum.
• Symptoms: Seedling damping-off, yellowing and wilting of leaves, vascular discoloration, stem lesions.
• Older plants may collapse suddenly, especially under stress.

• Survives in soil as chlamydospores for years.
• Primary infection from soil; secondary spread by water and wind.
• Management: Seed treatment (Carboxin/Carbendazim), crop rotation, use resistant varieties, balanced fertilization, maintain soil pH 6.5–7.0.

• Pathogen: Pseudomonas syringae pv. lachrymans (bacterium).
• Symptoms: Small, angular, water-soaked leaf spots; milky exudate under moist conditions.
• Lesions dry to form shot-holes; fruit spots cause internal decay and deformation.

• Seed-borne and survives in crop debris.
• Spread by irrigation water and handling wet plants.
• Management: Use pathogen-free seed, crop rotation, avoid overhead irrigation, apply bactericides (e.g., Streptomycin), destroy crop debris.

• Pathogen: Cucumber mosaic virus (CMV).
• Symptoms: Mosaic, leaf distortion, stunting, flower abnormalities, fruit deformation.
• Transmitted by aphids (non-persistent) and cucumber beetles; survives on weeds and alternate hosts.

• Rogue infected plants and eliminate weed hosts.
• Control aphid vectors with insecticides (e.g., monocrotophos, phosphamidon).
• Use resistant varieties where available.

• Pathogen: Tomato spotted wilt virus (TSWV), a tospovirus.
• Symptoms: Leaf bronzing, chlorotic spots, mosaic, die-back, stunting, fruit ring spots and necrosis.
• Transmitted by thrips (e.g., Frankliniella occidentalis, Thrips palmi).

• Use mesh screening and phytosanitary measures in nurseries.
• Avoid planting near thrips reservoirs (ornamentals, older crops).
• Control weeds and volunteer cucurbits.
• Implement early insecticide programs to manage thrips populations.

• Combine cultural, chemical, and biological methods for effective disease control.
• Use resistant varieties and certified seeds.
• Practice crop rotation and field sanitation.
• Monitor regularly for early detection and timely intervention.