Everything you need to know about controlling diseases of vegetables. Learn about how to control diseases of:- 1. Coriander 2. Fenugreek 3. Spinach 4. Mustard 5. Baby Corn 6. Ivy Gourd.
Contents:
- How to Control Diseases of Coriander?
- How to Control Diseases of Fenugreek?
- How to Control Diseases of Spinach?
- How to Control Diseases of Mustard?
- How to Control Diseases of Baby Corn?
- How to Control Diseases of Ivy Gourd?
1. How to Control Diseases of Coriander?
I. Wilt (Fusarium Oxysporum and Fusarium Coriandrii):
This is a serious disease of coriander and causes on an average 40-50% loss in Madhya Pradesh and Rajasthan. The disease is more prevalent in light soils and can attack the crop at any stage. The affected plants show yellowing and drooping of terminal portion followed by withering and drying of leaves, eventually resulting in death of plants, which can be pulled out of the ground easily. Partial wilting and discoloration of vascular bundles may also be seen if the disease infection is not severe. The growth of affected plants is arrested.
The fungus attacks the crop suddenly and capable of growing at a temperature from 12° to 35°C, however, the optimum temperature range for swift development is 24-27°C. High soil moisture favors the disease. The wilt is seen always more under irrigated than unirrigated conditions, because irrigation water plays a vital role in the spread of disease inoculums from one place to another place.
The disease is typically soil borne and not the seed borne. Since the infection arises in roots, it is tricky to control this disease, thus, following preventive measures may be taken into consideration to diminish the scope of this disease.
i. Follow soil solarization during hot summer by ploughing the field repeatedly.
ii. Adjust the soil pH 8.2 by applying oilcakes to reduce the incidence.
iii. Follow long crop rotation with non-host crops.
iv. Use only disease free healthy seed.
v. Avoid sowing in already fungus-infected fields.
vi. Follow late sowings in 1st and 2nd week of November.
vii. Treat the seed with Captan, Thiram, or Agrosan GN 2.5 g/kg of seed before sowing.
viii. Dress the seed and drench the soil with 0.2% carbendazim.
ix. Reduce irrigation frequency to keep the soil moisture low.
x. Seed pelleting with Trichoderma viride 4 g/kg of seed + neem cake application (150 kg/ha) reduces wilt incidence.
II. Powdery Mildew (Erysiphe Polygoni DC.):
The disease attacks the crop late in the season usually in February-Mach. Under warm humid conditions, the disease spreads very fast. In initial stages, the symptoms appear as small white or grayish specks on lower leaves, which later spread rapidly to stem, flowers and fruits. These small specks gradually enlarge and coalesce, covering the entire surface with floury mycelial growth and conidia of fungus. The young leaves are also soon affected. When the infection is severe, the leaves show an ashy-white appearance and dry up.
Flowers are so badly covered with mycelial growth that proper setting and development of fruits may not take place, and consequently, resulting in heavy yield reduction. The fruits if developed become light in weight. Under favorable conditions, the intensity of disease is so severe that the infected plants appear to be dusted with white flour.
The spread of disease under dry conditions is checked, and the temperature below 25°C has not been found favorable for the development of disease. The late sown crop grown under irrigated conditions is severely infected by this disease, which can destroy the crop absolutely, if adequate control measures are not taken timely.
Control:
i. Grow resistant/tolerant varieties.
ii. Treat the seeds with thiram or captafol before sowing.
iii. Foliar spray of onion extract (5%) is effective in reducing the severity.
iv. Dusting the crop with sulfur 5% dust @ 20-25 kg/ha and repeat 10-15 days later.
v. Spray the crop twice with 0.25% solution of wettable sulfur, 0.1% Karathane/Dinocap, Cosan, Calaxin, Sulfex, Thiovit, Morocide, or carbendazim.
III. Stem Gall (Protomyces Macrosporus Unger):
Coriander suffers most by the attack of gall forming fungus Protomyces macrosporus, which survives in soil for a long time and causes present day great economic loss than ever before due to manifests tumor like swellings on all aerial plant parts. The infection becomes systemic in the host stem before or during pre-flowering period. The affected leaves and fruits appear to lose their characteristic flavor and other properties.
Infected fruits become larger than the normal and poor in total fat content, free amino acids and sugar contents. Infection of this fungus reduces germination ability of seed markedly. Rise in atmospheric temperature lowers the infection due to change in host susceptibility. The incidence is severe in crops grown in alkaline soils with pH range 7.4 to 8.4 and the least incidence takes place in soils with 4.8 pH. Application of phosphatic fertilizers increases the intensity of disease, especially in the absence of nitrogen.
Control:
i. Follow long crop rotation with non-host crops.
ii. Follow soil solarization in hot summer months by ploughing the field repeatedly.
iii. Grow resistant variety like Karan (UD-41).
iv. Grow cv. Pant Haritima that had the lowest (3.2%) incidence of stem-gall
v. Grow late maturing varieties that showed greatest difference in disease severity
vi. Remove and burn all affected plant parts.
vii. Formalin 1% prevents chlamydospores germination absolutely.
viii. Spray the crop with penicillin and streptomycin at 400 mg/l after every 3rd weeks.
ix. Combined soil and seed treatment with Thiram or Emisan-6 @ 2.5 g/kg seed is effective.
x. Spray of Dinocap provides greater disease control.
xi. Spray with Thiram 0.2%, Captafol 0.2%, Carboxin 0.1%, or carbendazim 0.1% at fortnightly interval starting from the time of disease appearance.
xii. Treat the seed with Perenox, Agrosan GN, and Sulpha drugs like sulphathiazole and sulphadiazine at 0.1% concentration inhibits germination of chlamydospores.
xiii. Seed treatment with tetrachloronitroamisole (TCNA) at 0.5 kg/100 kg seed is effective.
xiv. Use bioinoculant Azospirillum or Azotobactor as seed treatment and soil treatment in combination with sheep manure 10 t/ha reduces the incidence up to 8%.
IV. Root Rot (Curvularia Pallescenns Boedjin):
The crop at seedling stage is susceptible more than the crop at later stages. The disease incidence at seedling stage has been estimated up to 50-75%, particularly under waterlogged conditions. The seedling roots due to the attack of this disease turn brown to black and the lower leaves give pale sick appearance.
The young leaves tips of severely infected plants show yellowing, which gradually spread downwards to the base of leaf, and later, the entire plants turn yellow and collapse due to rotting of basal portion.
i. Treat the seed with dry hot air at 53°C for 30 minutes.
ii. Drench the soil with formaline 0.4%, panogen 0.1%, or mercury sublimates.
iii. Drench the soil with Bavistin (carbendazim) 0.1% at least twice at 30 days interval.
V. Grain Mould (Fusarium Sp., Helminthos Orihlom and Curvularia Sp.):
The disease appears on grains when the mature dry seeds become wet due to rains at crop maturity stage and weather remains cloudy for few days as a result the grains turn white, grayish, and black, which adversely affect their appearance and market quality.
The disease affects the grains severely when the crop is harvested somewhat green and placed in stacks of bundles without drying properly by turning them daily. The disease also attacks the grains in storage if they are not dried precisely before storage or humidity in the storehouse is very high.
i. Harvest the crop at full maturity.
ii. Dry the produce properly to a safest moisture level.
iii. Store the seeds in cool and dry place.
iv. Spray the crop with 0.1% carbendazim (Bavistin) 20 days after flowering.
VI. Blight (Alernaria Poonensis):
The disease mostly appears under a condition of cloudy weather, and the symptoms appear as dark brown spots on stem and leaves. As a result, the appearance and quality of green leaves are affected severely, however, the disease is of minor importance, and its occurrence is sporadic.
Follow prophylactic spray of 0.2% Indofil M-45, or 0.1% Bavistin, especially under a condition of cloudy weather.
In addition, some minor diseases that appear sporadically in coriander are bacterial soft rot of leaves (Erwinia aroida), bacterial rot (Xanthomonas tranlucens), fungal stem rot (Rhizoctonia solani Kuhn), and seed-borne mycoflora such as Phoma multirostrata, Alternaria alternata, Fusarium moniliforme, F. semitectum and F. solani, etc. The diseases may be controlled through seed treatment and other measures adopted for control of major diseases.
The crop at flowering is susceptible to frost, which causes serious damage to coriander crop by affecting fruit setting adversely so it is essential to protect the crop from frost during flowering.
The following measures may be adopted to protect the crop from frost:
i. Adjust the sowing time so that flowering may not coincide with the occurrence of frost.
ii. Irrigate the crop when there is a danger of frost.
iii. Create smoke in environment around the field before sunset.
iv. Spray 0.1% sulfuric acid at flowering stage, and repeat after 10 days, if required.
2. How to Control Diseases of Fenugreek?
I. Root Rot (Rhizoctonia Solani Kuhn.):
This is soil-borne bacterial disease. The symptoms include varying degree of rotting of roots, leading to foliage yellowing in 30-45 day old plants. The affected plants wither and dry up. The problem may sometimes be serious, especially in fields where fenugreek is grown regularly, and may cause drastic yield reduction.
i. Adopt soil solarization and deep summer ploughing.
ii. Follow long crop rotation with non-host crops.
iii. Use disease free healthy seed.
iv. Grow only resistant varieties in disease prone areas.
v. Treat the seed before sowing with Trichoderma viridae @ 4 g/kg of seed.
vi. Use soil amendments like neem cake @ 10 q/ha and farm yard manure @ 10-25 t/ha.
vii. Treat the seed with 0.1% carbendazim or drench the soil twice with 0.1% carbendazim.
viii. Apply Trichoderma viride (5 kg/ha) + neem cake (150 kg/ha) in soil.
ix. Use bioinoculants, Azospirillum or Azotobactor to reduce the incidence of root rot to 8.2%.
II. Powdery Mildew (Erysiphe Polygoni D.C. and Laveillula Taurica Lev.):
The disease generally appears late in the season, and thus, is of minor importance. The symptoms include the appearance of whitish fungal growth on leaves. The disease that deteriorates the quality of leaves becomes serious at 15°-25°C temperature and relative humidity 60-70%.
i. Grow resistant/tolerant varieties.
ii. Spray sulfur 0.2%, Karathane 0.05%, or Calixin 0.05%.
iii. Dust the crop with sulfur powder at 20-25 kg/ha.
III. Downy Mildew (Peronospora Trigonella Gaum.):
This is also a fungal disease. Symptoms include the presence of yellow patches on upper surface and a cottony grayish-white mycelium at lower surface of leaves in the corresponding areas. In advance stages of infection, the leaves turn yellow and shed, and the plant growth is checked due to the attack of this fungus.
i. Give hot water treatment to seed before sowing.
ii. Spray any copper-based fungicides like Blitox, Fytolon, or Difolaton @ 0.2%.
iii. Spray the crop with Bordeaux mixture (1%).
IV. Damping Off (Pythium Aphanidermatum):
The fungus attacks the seedlings mostly at or below the collar region, which starts rotting, and the seedlings as a result topple down over the ground and wither off. The infected seedlings show water-soaked, discoloured and soft symptoms. High humidity coupled with moderate temperature favors the development of this disease.
i. Follow long crop rotation.
ii. Adopt repeated deep summer ploughing.
iii. Sow the seeds sparsely.
iv. Avoid excessive watering.
v. Use soil amendments like neem cake @ 10 q/ha and farmyard manure @ 10-25 t/ha.
vi. Drench the soil with 0.1% carbendazim, Brassicol, or Captan.
vii. Apply antagonistic fungi Trichoderma viride @ 5 kg/ha.
V. Leaf Spot (Cercospora Traversiana Socc):
This is a minor disease of fenugreek in India. Presence of round spots beneath the leaves, which are white at the center and brown at the periphery, indicates the disease. Such leaves drop-off prematurely and later symptoms also appear on pods. The occurrence of disease adversely affects the market quality of greens.
i. Follow at least 2 years crop rotation in infested areas.
ii. Use disease free healthy seed for sowing.
iii. Spray the crop with fungicides like Mancozeb 0.2%.
VI. Rust (Uromyces Anthyllidis):
This disease is of minor importance. Yellow spots bearing aecia in clusters are earlier symptoms. The disease is observed in the form of minute brown pustules on both the surfaces of leaves. In northern India, entire plant may be killed by the fungus under cool and wet climatic conditions.
Fungicide like Mancozeb is effective against this disease.
VII. Fenugreek Mosaic Wilt:
This is a virus disease transmitted by aphids. Symptoms include vein clearing, severe mottling, curling at the edges, leaf size reduction, stunting of plant and ultimately wilting. Young developing leaves are completely distorted, filiform and malformed. The disease causes severe losses on the part of leaf yield and quality.
i. Use disease free seeds.
ii. Remove all the infected plants and weeds.
iii. Spray the crop with 0.05% Malathion, 0.04% Quinalphos, or 0.03% Methyl demeton against virus vectors.
3. How to Control Diseases of Spinach?
I. Damping Off (Rhizoctonia, Pythium, Fusarium, and Phytophthora Spp.):
This is very common soil borne fungal disease. These fungi attack the seedlings at collar region near the ground. Due to their attack, the seedlings start rotting and collapsing. The disease may cause damage to the seedlings during germination or even after emergence. Many of the attacked seedlings die and fall over the ground. High humidity and moderate temperature favor the development of this disease.
i. Follow long crop rotation with non-host crops.
ii Sterilize the soil with formaldehyde (1 : 100 parts) about 2 weeks before seed sowing.
iii. Treat the seed with Captan, Foltaf, Captafol, or Agrosan GN 2 g/kg of seed.
iv. Drench the field with Captan at 0.1% solution.
v. Use less quantity of seeds per unit area.
vi. Avoid excessive irrigation.
II. Leaf Spot (Pliyllosticta Chenopodil Sacc. and Heterosporium Variabile Cke.):
This is a fungal disease. Leaves affected by Phyllosticta chenopodil fungus show light yellow specks, which develop into spot. Later on, the affected leaves are shriveled and dried up. The fungus Heterosporium variabile restricted to prickly seeded cultivar and causes dirty white water soaked circular spots on older leaves.
i. Grow disease tolerant/resistant cultivars of prickly-seeded type.
ii. Spray the crop with Blitox (copper oxychloride) 0.2%.
III. White Rust (Albugo Occidentallis Wilson):
This fungus causes white blister like circular or irregular pustules, which appear on the lower surface of the leaves, and opposite each blister on the upper surface, a yellow patch is developed. More than 80% yield is reduced due to this disease.
i. Keep the field free from weeds.
ii. Follow long crop rotation with non-host crops.
iii. Grow flat or smooth leaf cultivars, which are usually resistant than the Savoy or crinkled leaf cultivars.
IV. Downy Mildew (Peronospora Effusa):
The leaves affected by this fungus show light yellow irregularly shaped areas without distinct margins on their surface. Whitish-gray mycelium grows on leaf surface at high humidity, while the mycelium is generally found absent in low humid atmosphere. The disease develops in cool and moist weather. It appears at any stage of the plant.
The infection of downy mildew occurs primarily in the field but it becomes prominent after harvesting of crop, especially at 14-24°C temperature and > 85% relative humidity.
i. Use only disease free healthy seeds.
ii. Follow long crop rotation with non-host crops.
iii. Remove and destroy crop residues (debris).
iv. Spray the crop with Indofil M-45 or Indofil Z-78 at 0.2% at 15 days interval.
V. Anthracnose (Colletotrichum Spinaciae Ellis and Halsted):
This disease is caused by fungus in which affected leaves show water soaked spots. Later on, these spots coalesce and cause drying of the elongated grayish spots on seed. In case of seed crop of spinach black spots on seeds also form.
i. Use disease free healthy seeds.
ii. Remove and destroy the crop debris.
iii. Follow long crop rotation with non-host crops.
iv. Treat the seed with Captan, Thiram, or Bavistin @ 2 g/kg of seed or dip the seed in 0.125% solution of for half an hour.
v. Spray the crop with Indofil M-45, Indofil Z-78, Blitox, or Bavistin at 15-20 days interval
VI. Bacterial Soft Rot (Erwinia Carotonova):
It is a post-harvest bacterial disease causing severe losses of spinach in transit. The bacteria generally enter through wounds or via fungal lesions. Rotting occurs in the packed leaves due to lack of aeration and cleanliness. The infected leaves become gray-green and give a mushy look. Water-soaked areas are developed on the leaves. The decay progresses at a faster rate at high humidity and temperatures above 7°C.
i. Clean the harvested leaves before packing.
ii. Remove all the broken leaves before packing.
iii. Do not pack the leaves tightly.
iv. Send the harvested leaves immediately to the market.
v. Use clean packing material.
vi. Store the produce at perfectly cleaned place before marketing.
4. How to Control Diseases of Mustard?
A number of diseases have been recorded on this crop. Of these, some of the major diseases that adversely affected the quality and quantity of mustard greens as well as seed and oil yield making them unfit for human consumption are described below along with their control measures.
I. Alternaria Blight/Leaf Spot (Alternaria Brassicae):
This disease is most common in all the mustard growing states of India. The extent of damage ranged from 10 to 70%. Moist (more than 70% relative humidity) and warm (12-25°C temperature) weather with intermittent winter rains plays vital role for the development of this disease.
The pathogen perpetuates through seeds and affects the plant portion (refuse) in the soil. The disease is characterized by the appearance of concentric black spots on leaves, stems and siliquae. In years of severe outbreak, siliquae turn black in colour and may rot. Such siliquae contain shriveled and undersized seeds.
Control:
i. Follow crop rotation, which minimizes the inoculum buildup.
ii. Practice deep ploughing during summer season to eliminate the fungus.
iii. Use balanced fertilizers because heavy application of nitrogen makes the crop susceptible to the diseases.
iv. Avoid over irrigation and drain out excess water as high humidity favours pathogen development.
v. Sow the crop timely (10-25th October).
vi. Use only healthy and disease free certified seeds.
vii. Remove the weeds to reduce disease spread.
viii. Burn the crop debris of previous year.
ix. Spray the crop with iprodione (Roval) or mancozeb (Diathane M-45) @ 0.2 % (2 g/litre of water) at fortnightly interval soon after the disease appearance, maximum 3 sprays.
II. White Rust (Albugo Candida):
This disease occurs in all the mustard growing areas of India. It can be of serious menace if occurs along with downy mildew. The extent of damage ranges from 17.0 to 54.5% in case of mixed infection. Moist (more than 75% relative humidity) and cool (5- 12°C temperature) weather with short days (2-6 h sunshine) favours the disease development. The pathogen survives through oospores in crop residue, soil and as a contaminant of seed with diseased plant parts (primary inoculums).
White to creamy yellow pustules (1-2 mm in diameter) develop on lower side of the leaves at an early stage of the crop, i.e., 25-35 days after sowing if viewed critically which corresponds to tan yellow colour on the upper surface. In severe cases, white pustules also appear on stems and siliquae. These pustules burst and liberate a white powder.
Swelling and distortion of the stem and floral parts result into hypertrophy and hyperplasia, commonly known as staghead. In humid weather, mixed infection of white rust and downy mildew develop on staghead structure.
Control:
i. Follow crop rotation, which minimizes the inoculum buildup.
ii. Practice deep ploughing during summer season to destroy the fungus.
iii. Use balanced fertilizers because heavy application of nitrogen makes the crop susceptible to the diseases.
iv. Avoid over irrigation and drain out excess water as high humidity favours pathogen development.
v. Grow resistant varieties like Basanti, JM 1 and Maya.
vi. Sow the crop timely (10-25th October).
vii. Collect the seeds from staghead free plants to avoid carryover of the oospores.
viii. Treat the seed with metalaxyl (Apron 35 SD) 6 g/kg seed, or Thiram 2.5 g/kg of seed.
ix. Keep the crop field weed free.
x. Destroy the crop debris particularly stagheads of previous year crop.
xi. Avoid application of excessive irrigation.
xii. Spray the crop with Ridomil MZ-72 WR or mancozeb (Diathane M-45) @ 0.2% (2 g/litre of water) at fortnightly interval soon after the disease appearance, maximum 3 sprays.
III. Downy Mildew (Peronospora Parasitica):
This disease appears at young stage of the crop. Due to early infection, the crop plants become week and feeble, and ultimately, heavy yield losses are observed. The extent of damage and mode of survival of pathogen are similar to white rust. Disease development is favoured by cool (10- 20°C temperature) and wet (more than 90% relative humidity) weather.
In disease-affected plants, the yellow irregular spots appear on upper surface of the cotyledonary leaves at 10-15 days after sowing, and white growth is visible on under surface opposite to spots. If the attack is severe, the inflorescence is also affected. The affected inflorescence is malformed, twisted and covered with a white powder. No siliquae are produced on such inflorescence.
i. Follow crop rotation, which minimize inoculum buildup.
ii. Practice deep ploughing during summer season to eradicate the fungus.
iii. Use balanced fertilizers because heavy application of nitrogen makes the crop susceptible to the diseases.
iv. Avoid over irrigation and drain out excess water as high humidity favours pathogen development.
v. Grow moderately resistant variety (Narendra Ageti Rai 4) and moderately tolerant variety RLM 619.
vi. Sow the crop timely (10-25th October).
vii. Collect the seeds from staghead free plants to avoid carry over of the oospores.
viii. Treat the seed with metalaxyl (Apron 35SD) 6 g/kg seed or Thiram 2.5 g/kg of seed.
ix. Keep the crop weed free.
x. Destroy crop debris particularly stagheads of previous year crop.
xi. A void excessive irrigation.
xii. Spray Ridomil MZ-72 WP or mancozeb (Diathane M-45) @ 0.2% (2 g/litre of water) at fortnightly interval soon after the disease appearance, maximum 3 sprays.
IV. Sclerotinia Stem Rot (Sclerotinia Sclerotiorum):
This disease has been reported from Rajasthan, Uttar Pradesh, Uttaranchal, Madhya Pradesh, Chhattisgarh, Bihar, Haryana, Punjab, Delhi and West Bengal but it is most common in temperate regions. It is a soil borne disease and mono-cropping of mustard results in severe development of this disease in a specific geographical area. The extent of damage is up to 35% in low-lying areas. In individual affected plants, sometimes, no grain is formed.
This disease results in premature ripening of the crop and may cause additional yield loss due to the shattering of siliquae. High humidity (90-95% of relative humidity) and average temperature (18-25°C) along with wind current are the most favourable factors for the disease development. Elongated water soaked lesions develop on stem which are covered with cottony mycelial growth later on.
Affected plants look whitish from a distance especially at the base or at internodes. As such, the disease is also known as white blight. The affected plants show stunting and premature ripening, shredding of stem, wilting and drying. Grayish white to black spherical sclerotia develop either on the surface or in the pitts.
i. Follow long crop rotation with non-host crops like wheat, barley, rice and maize.
ii. Practice deep ploughing during summer season to make the field fungus free.
iii. Use balanced fertilizers because heavy application of nitrogen makes the crop susceptible to the diseases.
iv. Avoid over irrigation and drain out excess water as high humidity favours pathogen development.
v. Sow healthy seeds free from the sclerotial bodies.
vi. Burn the crop debris of previous year along with the sclerotia.
vii. Plough the field deep during hot summer.
viii. Spray carbendazim (Bavistin) 0.1% twice during flowering at 20 days interval at 50 and 70 days after sowing.
V. Powdery Mildew (Erysiphe Cruciferarum):
The disease is commonly observed in Gujarat, Rajasthan, Haryana, Maharashtra and southern part of the country. Yield losses vary considerably depending on the stage at which the disease occurs. High temperature (15-28°C), low relative humidity (60%) and low or no rainfall with wind current are most favourable factors for epidemic development of the disease. Infection first occur on the lower most leaves near the soil surface through Cleistothecia present in crop debris in the field (primary inoculum).
Dirty white circular floury patches develop on leaves, stems and siliquae. As the disease advances, the whole plant looks to be dusted with white talcum like powder. Minute spherical black fruiting bodies called Cleistothecia can be seen on the affected parts. The disease usually appears late in the season when temperature begins to rise.
i. Follow long crop rotation with non-host crops.
ii. Follow deep ploughing during summer to destroy the fungus.
iii. Use balanced fertilizers because heavy application of nitrogen makes the crop susceptible to the diseases.
iv. Avoid over irrigation and drain out excess water as high humidity favours pathogen development.
v. Grow resistant variety like GM-2.
vi. Sow the crop timely and avoid late sowing.
vii. Burn the crop debris of previous year.
viii. Spray wettable sulfur @ 0.2%, dinocap (Karathane) @ 0.1%, or carbendazim (Bavistin) @ 0.05% at the initiation of the disease.
5. How to Control Diseases of Baby Corn?
I. Downy Mildew (Sclerophthora Rayssiae):
The affected plant leaves show long and narrow yellowish parallel stripes, and purplish downy growth appears mainly on the lower surface of leaves, especially when the days are hot, nights cool and humidity is high. If the weather is hot or dry, only pale white patches are seen. Plant become pale, stunted, and bunchy and the affected leaves may die. As the infection proceeds, the purple irregular spots also develop on stems.
The fungus penetrates the leaf growing between leaf cells and sending fruiting branches above the leaf surface. These branches bear asexual spores (conidia), which are blown into the air and carried to the healthy plants by wind currents. Since irrigation water spreads the disease, thus, over watering should be avoided. This disease is soil as well as seed borne, and pathogen survives over-winter either on perennial hosts or on infected plant debris.
Control:
i. Use healthy and disease free seed.
ii. Provide proper drainage.
iii. Follow three years long crop rotation.
iv. Remove infected leaves, disease debris from the field and destroy them.
v. Treat the seed with hot water at 52°C for 30 minutes to kill the pathogens present on seed.
vi. Prophylactic sprays of mancozeb 0.25%, Indofil M-45 0.2%, or Indofil Z-78 0.2% 20 days after transplanting and repeat the spray at 10-12 days interval
II. Corn Smut (Ustilage Zeae):
The disease is apparent as black puffy masses on ears, tassels, and other parts of the plant. Early, open-pollinated yellow varieties of sweet corn are particularly susceptible to the disease.
Control:
i. Early removal and destruction of the infected plant parts check the further dissemination of spores of the pathogen.
ii. Treat the seeds with @ 2.5 to 4.0 g/kg of seeds.
III. Turcicum Leaf Blight (Helminthosporium Turcicum):
Long elliptic greenish brown lesions are formed, especially more severe on lower leaves, as a result the plants get burnt.
Control:
i. Treat the seeds with Captan, Thiram, or Agrosan GN @ 3 g/kg of seed.
ii. Prophylactic sprays of any of the fungicides, like mancozeb, Zineb, Maneb and Indofil M- 45 at 0.25% at 10-12 days interval should be followed.
IV. Maydis Leaf Spot (Drechslera Maydis):
The disease is characterized by the development of brown, small to large necrotic lesions on the leaves.
Control:
Follow protection measures that are taken for the control of turcicum leaf blight.
V. Stewart’s Wilt (Erwinia Steward Smith):
This disease sometimes causes severe losses, especially in the warmer regions, resulting in complete failure of very susceptible varieties. Root rot of baby corn is caused by a number of pathogens.
VI. Stalk-Rot (Cephalosporum Maydis):
The vascular bundles of infected plants become black, and consequently the growth becomes stunted. The upper leaves followed by lower leaves start drying, and finally, the affected plants are died.
Control:
i. Grow only the resistant varieties.
ii. Spray the crop with systemic insecticides to keep the insect-pests under control.
iii. Avoid mechanical injury to the plants.
VII. Bacterial Leaf Stripe (Pseudomonas Andropogonis):
The bacteria usually affect leaves below the ear, which show narrow, linear, and buff colored lesions that extend up on the leaf blade between the heavier veins. The disease is not so destructive since it is severe only on a few susceptible open pollinated varieties and hybrids.
Grow only the resistant hybrids/varieties.
VIII. Bacterial Soft Rot (Erwinia Carotovora):
This is most destructive disease, especially in humid weather. Excessive rain and irrigation also favor this disease. The infected plants show water soaked spots on stem bit above the ground level as a result the infected stem tissues start rotting at this point and the plants topple down over the ground. The bacteria of this disease survive in soil and decaying plant material.
i. Follow long crop rotation with non-host crop.
ii. Avoid application of sewerage water in field.
iii. Treat the seed with hot water at 52°C for 30 minutes.
iv. Spray the crop with 10 g Streptomycin or 50 g Agrimycin + Ceresan 2 kg/ha.
IX. Crazy Top (Sclerophthora Macrospora):
Infection results in excessive tillering, rolling, and twisting of upper leaves, and it is coupled sometimes with proliferation of tassels and/or ears into a mass of leafy structures. The infected plants produce no pollen since the flower parts in the tassel get completely deformed.
i. Provide adequate soil drainage.
ii. Keep the grassy weeds under control.
X. Maize Chlorotic Mottle Virus (MCMV) and Maize Dwarf Mosaic Virus (MDMV):
The synergistic infections of these viruses cause lethal necrosis. Infected upper leaves show bright yellow mottling or mosaic symptoms, which later turn dull yellow or camel colored. Death of leaves occurs from top to downward. Ears are reduced in size with small or aborted kernels.
i. Follow long crop rotation with non-host crops such as soybean, sorghum, or small-grain crops.
ii. Grow only the varieties and hybrids that are resistant to these viruses.
XI. Sting Nematodes (Belonolaimus Nortoni):
The nematodes damage the maize seedlings in young stage. Severely infected seedlings are died, and surviving seedlings are chloritic and stunted, resulting in less frugal plants that yield poorly.
The below ground roots show deep necrotic lesions, and root tips are frequently destroyed, resulting in thick and stubby structures.
i. Maintain adequate inter-row spacing.
ii. Adjust garlic in crop rotation to reduce the population of nematodes.
iii. Marigold as intercrop reduces the nematode population.
iv. Apply neem cake @ 80-100 kg/ha at the time of land preparation.
v. Apply Carbofuran 3G or Aldicarb at 25 kg/ha or Phorate 10 kg a.i./ha during field preparation.
vi. Soil fumigation with Nemagon or DD mixture at 20-25 kg/ha is effective for controlling nematodes.
6. How to Control Diseases of Ivy Gourd?
I. Powdery Mildew (Sphaerotheca Fulginea or Erysiphe Cichoracearum DC.):
Powdery mildew damages the ivy gourd crop in rainy season to the highest degree. White powder coating on upper and lower surface of the infected leaves is the symptom to recognize the disease. Sometimes, spots developed on the leaf, stem, petiole, and other parts, which later on turn brown and dry.
Severe infestations lead to stunted growth of plant and browning of leaves by leaf desiccation. High humidity, moderate temperature, low light intensity and heavy dew at night favor the development of spores but good conidial germination is observed within a temperature range of 22-31°C with optimum at 28°C and low relative humidity of 20% for less than 2 hours.
Control:
i. Collect and burn the plant debris.
ii. Follow long crop rotation with non-host crops.
iii. Spray fungicides like Kerathane 0.06% or Penconazol 0.05% at 10 days intervals.
iv. Spray tidermorph 0.05% or carbendazim 0.1% just after appearance of disease.
II. Downy Mildew (Pseudoperonospora Cubensis Berk. and Curta):
Downy mildew damages the ivy gourd crop severely in later part of rainy season. The spores of downy mildew perpetuate on various cucurbitaceous host due to continuous cropping and the prevailing conducive environment in rainy season. It is more virulent during long and cool nights (more than 11 h 30 min. and 18-22°C temperature).
Translucent yellowish spots appear on the underside of the leaves. When the leaves are examined early in the day, the conidia can be seen on the undersurface as a purplish downy growth. The conidia disperse after 8 a.m., and the disease symptoms are less marked and can be confused with a bacterial attack. When the disease reaches an advanced stage, the spots dry out and the leaf undergoes necrosis.
i. Follow clean cultivation with wider spacing in well-drained soil.
ii. Collect and burn plant debris immediately after harvest.
iii. Seed should be collected from disease free and healthy fruits.
iv. Spray sevimol @ 0.75 ml/liter of water to protect the disease.
v. Apply mancozeb @ 0.25% at 7 days intervals.
vi. In severe infestation, follow one spray of Metalaxyl + Mancozeb @ 0.2% to control the disease.
vii. Avoid the use of copper-based fungicides due to their phytotoxic effects, causing necrosis or marginal leaf chlorosis.
III. Fruit Rot (Colletotrichum Destructivum or Colletotriclium Lagenarium Pass.):
In ivy gourd, a considerable yield loss (60-75%) is reported in field condition due to fruit rot. Infection occurs on newly emerged shoots, fruits, and tendril. Light brown circular spots appear on the leaves, which later turn to deep brown. Elongated lesions are observed on stem and circular to oval sunken lesions on fruits, and subsequently, the fruits shrivel, show darkness, and finally, dry up. This disease infects fruits at both immature and mature stages.
i. Follow clean cultivation and wider spacing for planting.
ii. Follow at least 4 years crop rotation with legume or cereal crops.
iii. Spray Penconazol @ 0.05% regularly at 10 days interval.
iv. Spray systemic fungicide such as carbendazim (0.1%) to control the disease effectively.
IV. Gummy Stem Blight (Didymella Bryoniae):
Gummy stem blight is a serious problem in ivy gourd. Canker on stem, petiole, and fruit stalk, stem decay and wilt are some common symptoms appear during infection. Watery scoop exudates from the nodal portion of the stems, which turn yellowish brown gum, are other major symptoms.
i. Follow deep ploughing during summer.
ii. Use disease free healthy planting material.
iii. Collect and burn the disease debris.
iv. Harvest the fruits carefully to avoid injury.
v. Spray carbendazim 0.1% to reduce the infection.
V. Wilt (Fusarium Oxysporum):
Wilt is a soil born fungal disease, which can attack at any stage of plant growth. The major symptom is yellowing of plant and drying of infected leaves. The pink colour mycelia growth can be observed by digging the roots. Brown colour lining is developed inside the roots and translocation of nutrients is stopped.
i. Follow deep summer ploughing.
ii. Collect and burn the plant debris.
iii. Adopt crop rotation regularly.
iv. Treat the seedlings with Derosal (carbendazim).
v. Drench the soil with Captan, Hexocap, or Thiride 0.2-0.3% solution.
VI. Watermelon Mosaic Virus (WMV):
In ivy gourd, watermelon mosaic virus (WMV) is commonly prevalent throughout the growing season and transmitted through sap sucking insects like Aphis gossypii, Acalymma spp., Diabrotica spp., Epilachna spp. and Myzus persicae in a non-persistent manner. The symptoms appear on leaves in the form of curling mosaic or mottling accompanied by green vein banding and reduction in leaf size.
Sometimes, the petiole and internodes length also shortened. This virus checks the transmission of nutrients in the plant system. Since this crop is commercially propagated by stem cuttings, transmission through seed is having no meaning.
i. Use disease free healthy planting material.
ii. Follow wider spacing and clean cultivation in well-drained soil.
iii. Collect and destroy the infected debris from the field as soon as possible.
iv. Spray the crop with Dimethoate 0.1% (1 ml/liter of water) to reduce the population of whitefly.
v. Spray the crop with Oxytetracycline hydrochloride 500 ppm to control phyllody.
vi. Spray Emidacloprid @ 3 ml per 10 liter of water at regular interval to check the vector.