Everything you need to know about controlling diseases of vegetables. Learn about how to control diseases of:- 1. Cluster Beans 2. Indian Bean 3. French Bean 4. Bitter Gourd 5. Bottle Gourd 6. Round Melon 7. Luffa 8. Pointed Gourd 9. Snake Gourd 10. Beet Leaf.
Contents:
- How to Control Diseases of Cluster Beans?
- How to Control Diseases of Indian Bean?
- How to Control Diseases of French Bean?
- How to Control Diseases of Bitter Gourd?
- How to Control Diseases of Bottle Gourd?
- How to Control Diseases of Round Melon?
- How to Control Diseases of Luffa?
- How to Control Diseases of Pointed Gourd?
- How to Control Diseases of Snake Gourd?
- How to Control Diseases of Beet Leaf?
1. How to Control Diseases of Cluster Beans?
The common diseases affecting the crop are bacterial blight, Alternaria leaf spot, Myrothecium leaf spot, powdery mildew, anthracnose and dry root/basal rot. Two new fungal diseases, namely sclerotial disease caused by Pellicularia rolfsii and a new wilt caused by Neocosmospora vasinfecta, in cluster bean have been reported.
Some major diseases with their control measures are discussed below:
I. Bacterial Blight (Xanthomonas Axonopodis Pv. Cyamopsidis):
It is the most serious seed-borne bacterial disease, which usually occurs in Kharif season throughout the cluster bean growing areas of this country because high humidity, warm temperature (28- 30°C) and spattering rains favour the spread of this disease.
The disease appears as small, circular, and water-soaked spots on dorsal surface of the leaf, which coalesce to form bigger spots surrounded by chlorotic area on older leaves. Flaccidity of the affected portion due to invasion of vascular tissues turns the necrotic spots to brown and finally cause defoliation and occurrence of black longitudinal streak on stem.
i. Remove plant debris before sowing.
ii. Grow tolerant varieties, like RGC 471, HG 75, HG 182, and GAUG 63.
iii. Dip the seed in 0.02% aqueous solution of Streptocycline for 3 hours.
iv. Treat the seed with 0.025% Streptocycline in hot water at 56°C for 10 min.
v. Spray the standing crop twice with 250 ppm solution of Treptocycline.
II. Alternaria Leaf Spot (Alternaria Cucumerina Pv. Cyamopsidis):
This fungal disease is mainly prevalent in Haryana, Tamil Nadu, and parts of Rajasthan. The disease appears as dark brown round to irregular spots varying from 2 to 10 mm in diameter on leaf blades, which spread rapidly to form circular lesions under humid weather conditions. In severe cases, concentric rings of dark-brown conidiophores are developed and the leaflets become chlorotic, and usually drop off.
i. Spray the standing crop with zineb (0.2%) twice at an interval of 15 days.
ii. Apply iprodione, which enhances the activities of oxidative enzymes.
iii. Apply micronutrients, which are effective in controlling the disease.
iv. Grow tolerant variety, like HG 182.
III. Myrothecium Leaf Spot (Myrothecium Roridum):
This fungal disease is usually favoured by high temperature conditions, and appears as small to minute oil-soaked spots of 1-2 mm diameter, which later turn brown, coalesce and cover large area of leaf.
Spray the standing crop with 0.2% Indofil Z-78 five weeks after sowing.
IV. Anthracnose (Collectotrichum Capsici Pv. Cyamopsicola):
This fungal disease appears as brown to black spots on leaves, petioles, and stems during rainy season.
Spray the crop with Indofil Z-78 at 0.2%.
V. Powdery Mildew (Oidiopsis/Leveillulu Taurica):
The fungal disease appears as white mycelial patches dotted with the fruiting bodies on the abaxial leaf surface, stem, and even on pod, which is mostly prevalent in Karnataka, Gujarat, and parts of Rajasthan. Severely infected plants are defoliated and weakened by premature drying up and death of infected leaves.
i. Spray the crop with 0.025% Benomyl or 0.1% Dinocap.
ii. Grow tolerant variety, like GAUG 63.
VI. Dry Root Rot (Macrophomina Phaseolina/Sclerotium Rolfsii):
This disease caused by the seed and soil borne pathogens is most common in sandy soils of all cluster bean growing regions and favoured by warm temperature (28°-35°C) and moisture stress conditions during post flowering period. Reddish-brown discolouration on stem is caused initially, which becomes darkened with the formation of numerous small black sclerotia both inside and outside of tissues and on roots in advanced stage of attack, resulting production of very few pods.
i. Follow crop rotation with non-host or less susceptible crops, like moth bean, pearl millet, etc.
ii. Seed treatment with 0.2% Bavistin, which reduces seed-borne infection, improves germination and consequently leading to high fodder and seed yield.
iii. Grow tolerant varieties, like Kutch-8 and RGC 471.
iv. Mulching with crop stubbles (3.5 t/ha), which reduce plant mortality.
v. Drench the soil with quintozone 4 days prior to seed sowing.
2. How to Control Diseases of Indian Bean?
I. Alternaria Leaf Spot (Alternaria Alternata):
Circular to angular spots with gray center and reddish border appear on leaves. They gradually cover the entire leaf surface.
i. Crop rotation and destruction of infected plant debris are useful in checking the disease infection.
ii. Spray the crop with Indofil M-45 0.2% or Bevistin 0.1% at an interval of 10 days.
II. Ashy Stem Blight [Macrophomina Phaseolina (Tassi) Goid]:
Brown lesions, which spread rapidly covering the entire stem portion and killing the growing point, appear on collar region. Vascular tissues turn brown and rootlets rot ultimately causing plant death. It is seed borne disease.
i. Use only disease free seed.
ii. Treat the seed with Thiram or Captan/Captaf @ 2-3 g per kg of seed.
III. Powdery Mildew (Laveillula Taurica Var. Macrospora):
It attacks almost all parts of the plant. First whitish powdery mass appears on leaves and then spread onto the stem and pods. Defoliation occurs in severe cases. The disease is more severe under dry weather conditions.
Spraying of wettable sulfur 0.5% can control the disease.
IV. Bacterial Leaf Spot (Xanthomonas Phaseoli):
Bacterial leaf spot is most destructive disease of Indian bean. The disease not only reduces total yield but also affects quality of pods, thus, rendering them unmarketable. The disease intensity is more on younger plants than on older ones.
At initial stages, small, round or irregular water soaked lesions, which later turn to reddish or brownish with yellow halo spots, appear on leaves. In severe cases, several such spots coalesce and leaves turn yellow resulting in defoliation.
Spray of Agallol @ 1000 ppm and Agrimycin @ 200 ppm completely inhibits the pathogen growth.
Leaves of the diseased plants are reduced in size, and they develop blight yellow patches interspersed with green areas. It is a viral disease spread by the insect vector white fly (Bemisia tabaci).
i. Uproot and destroy the infected plants.
ii. Spray Rogor or Metasystox 1 ml/l of water at 10 day intervals to control the virus vectors.
3. How to Control Diseases of French Bean?
I. Anthracnose (Colletotrichum Lindemuthiatium):
Dark brown black sunken lesions appear along the leaf veins on underside of leaves. On pods, the brown to black circular sunken lesions with light grey margins characterize this disease. The infection may extend to the seeds, which carry the fungus from season to season. Stems of seriously affected plants may break, causing them to topple.
The fungus can survive from one season to another on debris of infected plants and diseased seeds as well. Optimum range of temperature and humidity for disease development is 18° to 27°C and 90 to 100%, respectively. Disease incidence has been found to increase with the age of plant.
i. Follow crop rotation of at least 2-3 years.
ii. Seed treatment with bavistin or benomyl (0.2%) has proved very effective.
iii. The severity of disease spread can also be reduced by spraying with mancozeb (0.25%) or carbendazim (0.05%), and may be repeated at 10-15 days interval, if required.
II. Angular Leaf Spot (Phaeoisariopsis Griscola):
Reddish brown spots appear on leaves, turning them yellow and leading to their defoliation. Sometimes, the spots are dark brown to grey with a distinct margin and are angular. Severely spotted leaves show premature senescence and drop off. The disease occurrence is severe in wet weather, and fungus can survive 2-3 years on residues from diseased plants in soil. Infection-sometimes also carries to seeds, which in turn show yellow discoloration.
i. Follow long crop rotation with non-leguminous crops.
ii. Destroy the disease debris from infected crops.
iii. Treat the seed with carbendazim (0.2%).
iv. Spray the crop with mancozeb (0.25%), combination of mancozeb (0.2%) and carbendazim (0.05%), or hexaconazol (0.05%).
III. Floury Leaf Spot (Mycovellosiella Phaseoli):
Characteristic symptoms include the appearance of floury patches on underside of leaves followed by necrosis. The corresponding upper surface shows brown spots with yellow margins.
i. Collect the infected plant debris and destroy them.
ii. Always use disease free healthy seed for sowing.
iii. Spray the crop with Bavistin/Benomyl (0.1%) and repeat at 10 days interval, if required.
IV. Root Rot (Rhizoctonia Solani):
Root rot shows the characteristic symptoms, which appear initially on roots and then on stems with reddish brown sunken spots near the soil line and leading to complete rotting of root system. Root rot should be suspected whenever plant withers and dies, leaves turn yellow and drop off, and plants are stunted.
Control:
i. Follow long Crop rotation.
ii. Use healthy and disease free seed.
iii. Treat the seed with carbendazim (0.2%).
iv. Spray the crop with carbendazim (0.1%), mancozeb (0.25%), or combination of mancozeb (0.2%) and carbendazim (0.05%) and repeat after 10-15 days, if required.
V. Common Blight (Xanthomonas Axonopodis Pv. Phaseoli):
Small water soaked lesions and yellowing of interveinal areas of leaves are recorded as the characteristic symptoms of common blight. Small water soaked spots surrounded by distinct zones of narrow reddish-brown or brick red band of tissues appear on pods. Discolouration near the helium region of seed is also recorded as a distinguish symptom of this disease.
Control:
i. Collect and destroy the infected plant residues and weeds.
ii. Follow long crop rotation.
iii. Use healthy and disease free seed.
iv. Treat the seed with Streptocycline and Captan @ 0.01% and 0.25%, respectively.
v. Spray the crop with Blitox 0.35% as and when the disease symptoms appear.
Bean common mosaic virus (BCMV) and bean golden mosaic virus are the two common similar viral diseases of beans. BCMV produces chlorotic, crinkled, and stiff young-leaves as primary symptoms, and secondary symptoms are produced on half-blade of trifoliate leaves as general chlorosis and mottling with definite pattern of dark and light green areas.
The compound leaf shows downward curling and rolling, which differentiate the disease from BYMV. Both the viruses are mechanically transmitted and Myzus persicae is a common aphid vector transmitting the disease. BCMV is also transmitted through seed.
Control:
i. The only alternative is to use resistant varieties/lines like CO-40696 developed by Brick et al. (2002).
ii. Germplasm lines USCR-7 (PI 618811) and USCR-9 (PI 618812) possess the ‘be’ gene, which conditions an immune reaction to the BCMV and BCMNV strains from USDA-ARS (USA).
iii. Cultural practices like adjustment in sowing time, especially planting in the Aphid free periods also helps in reducing the attack of viruses.
iv. Intercropping of bean with maize also proved effective in lowering down the disease incidence.
v. Always use healthy and disease free seed form a certified source.
4. How to Control Diseases of Bitter Gourd?
I. Anthracnose (Colletotrichum spp.):
Bitter gourd is very less affected with this disease. Symptoms appear on all aerial parts of bitter gourd plant. The spots on the foliage begin as small yellowish or water soaked areas that enlarge rapidly and later turn brown. The spots on fruits are roughly circular, sunken, water soaked with dark borders and of considerable size. Red gummy exudates may appear on lesions.
Control:
i. Field sanitation by burning crop debris is advised to prevent further infection.
ii. Seed treatment with carbendazim or Captan @ 2.5 g per kg of seed is recommended.
iii. Foliar spray of carbendazim (0.1%) or chlorothalonil (0.2%) before infection is recommended.
II. Downey Mildew (Pseudoperonospora Cubensis):
Bitter gourd is less susceptible to downy mildew. This disease is very common in northern India, particularly on bottle gourd, ridge gourd, muskmelon, and cucumber. It becomes serious during later part of rainy season. The first symptom on the leaves resembles as symptom of mosaic mottling. The pale green areas are separated by darker green boundaries.
Soon the spots well defined, become irregular, yellow colored and restricted by the veins of the upper surface. In moist weather, a purplish downy growth appears on undersurface of the leaf, however, the growth is not very pronounced in dry weather. Young leaves are less susceptible than older ones. Infection occurs more readily on lower surface than on upper surface.
Control:
i. Crop should be grown in well-drained soil with wider spacing.
ii. Burning of crop debris is advocated to reduce the inoculums.
iii. Two protective sprays of mancozeb (0.25%) at 7 days interval give good control.
iv. In severe infestation, one spray of metalaxyl + mancozeb (0.25 %) may be applied.
III. Powdery Mildew (Sphaerotheca Fuliginea Syn. Erysiphe Cichoracearum):
Bitter gourd is less infected with powdery mildew. The symptom is appeared as white to dirty gray tiny spots on the foliage and green stems, which on enlarging become powdery. The superficial powdery mass may ultimately cover the entire green surface of the leaf.
Control:
i. The disease crop debris should be collected and burnt.
ii. Regular spray of fungicides such as penconazole (0.05 %) or carbendazim (0.5-1.0 g/liter) or Calixin (1.0 g/liter) is effective to minimize the disease incidence.
IV. Alternaria Blight and Leaf Spot (Alternaria Cucumerina Elliot):
This disease causes damage in summer squash, pumpkin, snake gourd, and bitter gourd too. The yield losses reported are about 77% in bitter gourd and 80% in pumpkin. The initial infection is noticed as small spots on leaves, which rapidly increase in number and size.
In advance-stages, the burning effect and blight symptoms are also seen after coalescing of adjoining spots. The pathogen perpetuates in soil on plant debris. A temperature of 25-30°C coupled with 92-100% relative humidity is the most ideal condition for the growth and spread of this fungus.
Control:
i. Collecting and burning of plant debris are effective for reducing inoculums.
ii. Following crop rotation for at least 3 years is advantageous for reducing inoculums.
iii. Providing proper drainage reduces the incidence of this disease.
iv. Borax wash (2.5%) at 45°C for 30 seconds before packaging of fruits reduces incidence in storage.
Viral Diseases:
Bitter gourd is susceptible to viral diseases. In severely infected early crops, the yield loss may be up to 100%.
Some important viral and mycoplasmal diseases of bitter gourd, their mode of transmission, symptoms, and management practices are briefly described below:
The leaves of infected plants develop vein clearing, scattered small yellowish patches, and reduction of leaf lamina. Severe mosaic symptoms in bitter gourd are characterized by typical mosaic, upward leaf curling, crinkling, mottling and severe stunting. Inoculated plants show typical symptoms of mosaic and leaf curling at 8-12 days after inoculation.
Early flower shed results in reduction of yield, but the fruits that develop on diseased plant appear normal. Transmission studies in India show that the mosaic virus in bitter gourd is transmitted through mechanical means, grafting and by the aphid vectors, Aphis gossypii, Aphis malvae, Myzus persicae and Aphis craccivora. There is no evidence of disease transmission by seeds.
Still no information is available on the management of this disease.
b. Gemini Viruses:
Gemini viruses have been found to be associated with bitter gourd, pumpkin, and muskmelon. The Gemini virus infecting bitter gourd is not transmitted by sap inoculation but it is easily graft-transmissible and efficiently transmitted by whitefly in a persistent manner. The virus is also seed borne in bitter gourd.
i. Collect seeds only from healthy plants and always use disease free seed.
ii. Collect disease debris from the bitter gourd field and burnt them.
iii. Foliar spray of Dimethoate (1.0-1.5 ml/litre) is effective in reducing whitefly population.
5. How to Control Diseases of Bottle Gourd?
I. Powdery Mildew (Sphaerotheca Fuliginea):
Powdery mildew is a fungal disease that appears very severely in dry season on underside of leaves. Severely infested leaves become brown and shriveled.
Control:
i. Seed treatment with systemic fungicides also gives protection to young seedlings.
ii. Spray carbendazim (0.1%), Thiophenate M 0.05%, Calaxin 0.05%, Karathane 0.5%, or Sulfex 0.2% at fortnightly interval, however, the best control of powdery mildew on bottle gourd was given by 1-2 sprays of Calixin (tridemorph), followed by Bavistin (carbendazim) and Sulfex-80. In terms of the cost-benefit ratio, Sulfex is recommended.
II. Downy Mildew (Pseudopernospora Cubensis):
A fungal disease appears under humid conditions, especially when rains frequency is very high. The symptoms appear as more or less angular yellow spots on upper surface of leaves. The disease spreads very fast and kills the plants quickly.
Control:
i. Spray Indofil M-45, Daconil, Difolatan, or copper oxychloride 0.2%.
ii. Chlorophyll ‘a’ and ‘b’ contents, and NPK contents increased in leaves of bottle gourd after spraying with hexaconazole.
III. Anthracnose (Colletotrichum Sp.):
The disease is characterized by dark necrotic lesions with pointed ends on petioles and stem. In case pedicels of fruits are infected, young fruits shrivel, darken, and finally dry up. Lesions on fruits are circular, water soaked, sunken, dark brown to black and variable in size, depending upon plant age and weather conditions.
Control:
Apply Indofil M-45 0.2% or Bavistin 0.1% as foliar spray at 10-12 days interval.
IV. Fusarium Wilt (Fusariuin Solani):
In early stages, cotyledons drop and plants wither. In older plants, leaves wilt suddenly and vascular bundles in the collar region become yellow or brown. It is easy to restrict the spread of disease but once the disease is spread, it is difficult to check. The endogenous level of auxin appeared to play a major role in the pathogenesis of bottle gourd wilt.
Young leaves and stems of infected plants showed 175 and 154% endogenous auxin, respectively, in comparison with healthy plants. The higher level in infected plants resulted from lower activity of IAA oxidase. In resistant plants, auxin activity declined after an initial increase at 20 and 40 days after sowing. In susceptible plants, the auxin level remained high at 60 days, causing extensive tylosis and wilt.
Control:
i. Use disease free healthy seeds.
ii. Cultivate resistant varieties
iii. Drench the soil with Captan 0.2 to 0.3%.
V. Rhizoctonia Root Rot (Rhizoctonia Solani):
The fungus causes both pre- and post-emergence mortality of seedlings. However, older plants are less susceptible to this disease.
Control:
i. Follow long rotation with non-host crops.
ii. Treat the seed with Vitavex or Brassicol 3-4 g/kg of seed.
iii. Drench the soil with 0.2% Brassicol.
VI. Mosaic Disease:
A large number of viruses attack the bottle gourd crop and cause serious damage. The leaves show symptoms like mosaic mottling, crinkling, and twisting. Internodes are shortened and flowering is affected adversely. In rainy season, insects like whitefly spread the viruses rapidly. Watermelon mosaic virus 1 (watermelon papaya ringspot potyvirus) infects this crop under field conditions, reducing yield and fruit quality.
Infection during the early stages of growth (5-30 days) caused up to 100% loss in yield. However, the plants infected at 40-70 day were affected less severely, and thus, produced 3-6 fruits per plant as compared with 6-7 fruits from healthy plants. Fruits from infected plants were small, blistered, and unfit for marketing.
Control:
i. Collect the seeds from virus free plants.
ii. The only solution is to develop and grow cultivars resistant to virus.
iii. Spray the crop with systemic insecticides like 0.05% Malathion at 5-7 days interval to control the virus vectors.
6. How to Control Diseases of Round Melon?
I. Powdery Mildew (Sphaerotheca Fuliginea Schelcht Fr.):
Powdery mildew is caused by Sphaerotheca fuliginea Schelcht Fr. and Erysiphe cichoracearum during winter season. Initial symptoms appear as white or fluffy circular patches or spots on under surface of older leaves. The whitish powdery growth covers most of the leaves and leads to heavy reduction in photosynthesis. Sometimes, due to severe infestation, defoliation may occur and growth of plant and fruits seized.
i. Destroy the crop residue as soon as possible.
ii. Follow clean cultivation practices to suppress the host plant near by the field.
iii. Spray carbendazim (0.1%), thiophanate M (0.05%), Calixin (0.05%), Karathane (0.5%) or Sulfex (0.2%) at fortnightly interval.
II. Downy Mildew (Pseudopernospora Cubensis):
Downy mildew is caused by Pseudopernospora cubensis during summer. Symptoms appear as irregular, numerous, small, yellow angular spots surrounded by green tissues scattered all over the leaf lamina. It appears just like in a definite mosaic pattern. It spread promptly in the field when humidity increased. The severe disease attack kills the plant quickly through rapid defoliation.
Control:
i. Grow the crop at wider spacing in well-drained soil.
ii. Plough the field deep in hot summer months.
iii. Follow long crop rotation with non-host crops.
iv. Collect seed from healthy crop and use disease free seed.
v. Air movement and sunlight exposure helps in checking the disease initiation and development.
vi. Keep the field clean by burning disease debris to reduce the inoculums.
vii. Seed production should preferably be carried out in summer season.
viii. Spray Griseofulvin (100-1000 ppm) isolated from Penicillum griseofulvum.
ix. Follow protective spray of Indofil M-45, Daconil, or Difoltan 0.2% at 10 days interval or mancozeb 0.25% at 7 days interval.
III. Anthracnose (Colletotrichum Orbiculare):
Anthracnose is a common problem of this crop during rainy season. Disease symptoms are found on all above ground plant parts started from cotyledonary leaf to fruits. It can be identified easily by small yellowish water-soaked areas, which enlarge in size and turn brown to black in colour. The necrotic portion dries and shatters. Girdling of branches and dark brown circular lesions on fruits are secondary symptoms.
i. Collect seed from healthy fruits and disease free area.
ii. Treat the seed with carbendazim 0.25%.
iii. Keep the field clean by burning disease debris.
iv. Maintain proper drainage in the field.
v. Spray chlorothalonil @ 0.2% just after notice of infection.
vi. Spray systemic fungicides such as Benomyl, Bavistin or thiophanate M (0.1%) for effective control.
IV. Fusarium Wilt (Fusarium Oxysporum):
A soil borne fungus attacks the crop at young seedling stage. As a result, the cotyledons drop down and wither. The older plants leaves wilt suddenly and vascular bundles in the collar region become yellow or brown.
i. Treat the seed with carbendazim @ 2 g/kg of seed.
ii. Drench the soil with Captan, Hexocap, or Thiride @ 0.2-0.3% solution.
V. Gummy Stem Blight (Didymella Bryoniae):
Initially water soaked areas are observed on the stem near soil line. Later on translucent gum like exudates released from the affected portion are deposited over it. Black dot like pycnidia is also observed on the affected bark.
i. Follow summer ploughing and green manuring followed by Trichoderma application.
ii. Maintain proper drainage and aeration in the field.
iii. Treat the seed with carbendazim @ 0.25%.
iv. Drench the soil near collar region with 0.1% carbendazim.
v. Avoid injury near collar region.
VI. Rhizoctonia Root Rot (Rhizoctonia Sp.):
Rhizoctonia root rot disease causes both pre- and post-emergence mortality of seedlings to a greater extent and older plants to a lesser extent. It is more prevalent in areas where cultivation is done during rainy season. Lesions start developing on stem near collar region at or below the soil level and move downward into the roots.
Initially, the bark becomes wet and soft with macerated tissue, and later on, drooping and wilting of plant is observed. Disease is more common in poorly drained soil and the fields having prolonged excessive moisture.
i. Follow long crop rotation with non-host crops to reduce inoculums.
ii. Uproot and burn the infected plants.
iii. Summer ploughing followed by irrigation in between April and June, and then, again ploughing reduce the activated soil inoculums.
iv. Treat the seeds with vitavax or brassicol @ 2 g/kg of seed.
v. Drench the soil with Trichoderma @ 1% suspension after germination.
VII. Fruit Rot (Phythium Aphanidermatum and Phytophthora Cinnamoni):
Fruit rot is a common problem of round melon during Kharif season. The infestation of fungus produces water soaked spots, and soft rotting of the fruits starts from lower portion, which is close to moist soil. In early morning, white fluffy mycelium web growth can be observed on the affected portion. Relative humidity of 70-90% favors the mycelium web growth.
i. Keep the fruits away from moist soil by adopting bower system of cultivation.
ii. Adopt single plant staking to avoid disease incidence.
iii. Proper drainage in the field
iv. Green manuring followed by soil application of Trichoderma @ 5.0 kg/ha in soil is very effective in checking most of the fruit rotting.
v. Collect affected fruit and burn them to reduce primary inoculum.
7. How to Control Diseases of Luffa?
I. Powdery Mildew (Sphaerotheca Fulginea):
The fungus forms a white floury coating on leaves, stem, and other succulent parts of the plant in dry weather. The superficial powdery mass may ultimately cover the entire green surface of the host. The severely attacked leaves become brown and shriveled, and premature defoliation and death of the vines are occurred. The fruits get undersized and deformed.
i. Remove the weeds around the field.
ii. Destroy the disease debris by burning.
iii. Treat the seed with Thiram/Captan 2.5-3 g/kg of seed.
iv. Drench the soil with Thiram/Captan dissolving 2 g/litre of water.
v. Spray the crop with Karathane, Bavistin, or Calixin 0.1%, or 0.2% Sulfex.
II. Downy Mildew (Pseudoperonspora Cubensis):
The disease is found prevalent in areas of high humidity, especially when summer rains occur regularly. The early symptoms on leaves resemble those of mosaic mottling. The pale green areas are separated by islands of darker green, which become well defined with visible symptoms of small water soaked lesions on the leaves. These lesions appear yellow on upper surface and grayish downy growth of fungus develops on lower surface of leaves. Later these lesions turn brown in the center and veins are blighted.
i. Destroy over wintering vines.
ii. Spray Indofil M-45 (0.3%) at weekly interval.
iii. Spray Ridomil MZ (0.2%) at weekly interval under a situation of heavy disease risk.
III. Collar Rot (Rhizoctonia Solani):
The fungus also known as Rhizoctonia root rot causes mortality at pre- and post-emergence stages. The stem shows brown to dark brown lesions at the level of soil, which eventually kill the plant. The older plants are less susceptible than the younger ones. The fungus also causes damping off disease of seedlings in nursery.
i. Follow crop rotation with non-host crops.
ii. Treat the seed with Vitavax, Brassicol, or Thiram @ 3 g/kg of seed.
IV. Pythium Rot (Pythium Butleri):
The water soaked lesions girdling the stem extend upwards and downwards. The affected tissues start rotting, and even grown up plants start collapsing. The disease appears as a luxuriant wooly mycelial growth on the affected fruits, which appear as if wrapped in cotton. The fruits in contact with soil suffer most.
On the margin of cottony growth, the skin of the fruit looks dark green and water soaked. The fruits become watery and soft and emit foul smell. The disease is common in the field on fruits lying on the ground. It also spreads among fruits during transit and storage.
i. Treat the seed with Thiram or Bavistin @ 3 g/kg of seed.
ii. Avoid flood irrigation, especially in hot hours.
iii. Avoid direct contact of fruits with the soil.
iv. Maintain sanitary conditions during transportation and storage.
The small greenish-yellow areas those are more translucent than the remaining parts developed on young leaves. The leaves become chloritic, reduced in size and deformed into finger like structure at the end of season. Plants show stunted growth and yellow mottling appears on fruits. The cucumber mosaic virus is transmitted through sap, seeds, and aphids.
i. Collect seeds from virus free plants.
ii. Rogue out and destroy the virus-infected plants including weeds.
iii. Spray the crop with Dimethoate 0.05%, Monocrotophos 0.03%, or endosulfan 0.05% at weekly interval to control the virus vectors, i.e., aphid.
8. How to Control Diseases of Pointed Gourd?
I. Rot Disease (Pythium Spp. and Phytophthora):
The incidence of shoot and fruit rot caused by soil borne fungi is mostly seen in rainy season, particularly when water stagnation occurs. The fungi attack the tender shoots, leaves, and fruits as a consequence white cottony growth develops on the affected plant parts. The spread of fungi is aggravated through rain splash and irrigation water.
The other soil borne fungus, Macrophomina phaseolina, causing collar rot attacks root and collar region of the vines and the affected portion gradually rot and finally become dry. This disease becomes rampant in the crop preceded by jute.
Control:
i. Grow the crop on raised beds with good drainage facility to avoid water stagnation.
ii. Spray the crop with Blitox or Fytolan @ 4 g/litre of water at 7-10 days interval.
II. Cucumber Green Mottle Mosaic Virus (CGMMV):
The causal virus (Tobamo virus), an undeveloped rod shaped virus, causes irregularly distributed chlorotic spots on leaf lamina. It is transmissible by contact and mechanical inoculation. Vectors of the virus are not confirmed. The virus is carried over through seasons by infected crops, weeds and contaminated seed materials.
III. Cucumber Mosaic Virus (CMV):
The virus particle, an isometric cucumo virus, causes mosaic mottling, irregularly distributed yellowish patches and green vein banding with deep brown to blackish vein areas on the lamina. It is transmissible by mechanical inoculation and vectored by aphids (Aphis gossypii and Myzus persicae) but it does not persist in vectors. The inter-seasonal carryover of virus occurs through infected crops, weeds and contaminated seed materials.
Control:
i. Destroy the infected crop plants and weeds to check the carryover of virus.
ii. Spray the crop with imidacloprid (5 ml/10 litre of water) to control the aphids, which are the vectors of this virus.
9. How to Control Diseases of Snake Gourd?
I. Anthracnose (Colletotrichum Lagenarium (Pass.) Ellis & Halsted):
The disease infects all the above ground parts of the crop. Yellowish water-soaked areas, which coalesce with each other on enlarging, and turn brown to black, appear on leaves. The necrotic portion gets dried and shattered.
Elongated water-soaked sunken lesions also appear on stem. Light yellow to brown discoloration of the stem lesions takes place due to abundant sporulation. Sunken dark brown to black lesions, which vary in size, also appear on fruits, depending upon age of the crop plants and weather conditions.
i. Field sanitation by burning of crop debris reduces the primary inoculums.
ii. Always collect seed from healthy fruits and disease free fields.
iii. Seeds must be treated with carbendazim or Captan @ 2.5 g/kg of seed.
iv. Foliar spray of Chlorothalonil 0.2% gives good control of the disease but spray must be started before the infection occurs.
v. Foliar spray of fungicides such as Benomyl, Bavistin, and Thiophanate-M (0.1%) reduces the disease incidence.
II. Downy Mildew (Pseudoperonospora cubensis (Berk. & Curt.) Rosto.):
Symptoms appear as numerous small irregular yellow lesions surrounded by green tissues scattered all over the leaves. In due coarse of time, lesions grow in size and coalesce with each other. Old lesions become necrotic, and are clearly demarcated with slightly yellowish areas.
Severely infected leaves roll upward with brownish tinge that produces a blighted appearance. Grayish black downy fungal growth is observed on under surface of the leaf. Crop should be grown with wide spacing on well-drained soil.
i. Field sanitation by burning crop debris helps in reducing the inoculums.
ii. Protective spray of mancozeb (0.25 %) at seven days interval gives good control.
iii. In severe cases, one spray of metalaxyl + mancozeb @ 0.2% may also be done.
III. Powdery Mildew (Sphaerotlieca Fuliginea (Schlecht.) Pollacci.):
The infection appears first on upper side of the leaves and stem as white to dull white powdery growth, which quickly covers most of the leaf surface and leads to serious reduction in photosynthetic rate. In due course of time, all the above ground parts are infected. Finally, the lesions turn brown and necrotic. The affected leaves become yellowish, dry, and get defoliated. The fruits do not develop properly, and sometimes, covered with white powdery masses.
Control:
i. The fungicidal spray of penconazole (0.05 %) can give very good control of the disease.
ii. Spray the crop with Karathane 1.5 ml/liter, carbendazim 0.1%, Calixin 0.1%, or Sulfex 2.5g/litre.
IV. Fusarium Root Rot (Fusarium Solani F. Sp. Cuciirbitae Snyder & Hansen):
The symptoms include vascular browning, gummosis, and tyloses in xylem vessels of mature plants, and subsequently the whole plant gets wilted. The pathogen is both seed and soil borne.
Control:
i. Follow long crop rotation and clean cultivation.
ii. Use only disease free healthy seed.
iii. Grow resistant varieties in disease-infested areas.
iv. Avoid root injury during intercultural operations.
v. Soil application of Trichoderma (5 kg/ha) during soil preparation is advantageous.
Mosaic:
Mosaic caused by CMV is also prevalent in snake gourd. Joseph and Menon (1978) also reported the mosaic diseases in snake gourd. Symptoms include a mosaic with dark green raised blisters on the leaf lamina, reduced leaf size, shortened-internodes, and retarded growth. Infected plants flowered sparingly and set only few fruits. The virus is sap and insect (Aphis gossypii and Aphis craccivora) transmissible.
Aphis craccivora acquires this virus with 5 minutes acquisition feeding and transmits it with 5 minutes feeding on healthy plants. A minimum of 5 aphids is required for its transmission. The vector could not retain the virus for long periods, the relationship being non-persistent. The virus was identified as a strain of Cucumis virus-1 (cucumber mosaic virus).
Management of Mosaic:
The most effective management of viral diseases demands integration of management practices such as avoidance of sources of infection, control of vectors, modification of cultural practices and resistance of host plant. Rouging and destroying of virus-infected plants is an effective measure to restrict the spread of mosaic disease.
10. How to Control Diseases of Beet Leaf?
I. Damping Off (Phythium Ultimum and Rhizoctonia Solani):
It is a very serious soil borne fungal disease, which causes damage to the seedlings during germination or even after emergence of seedlings. The fungus attacks the seedlings at a region of the stem touching the ground. Many of the attacked seedlings die and fall over the ground.
i. Follow long crop rotation with non-host crops.
ii. Treat the seeds with Captan or Thiram at 2.5-3.0 g/kg of seeds before sowing.
iii. Avoid excess moisture by providing optimum quantities of irrigation water.
iv. Drench the soil with Captan 0.2% + Bavistin 0.1%.
II. Leaf Spot (Cercospora Beticola Sacc.):
Small dot like circular spots with ash colour center and deep violet or reddish purple border appear on the lower leaves. Later, these spots coalesce and turn to lesions covering the whole leaf as a result the leaves wrinkle, and ultimately, dry and fall down.
i. Remove all previous crop plant residues (debris).
ii. Follow long crop rotation with non-host crops.
iii. Grow tolerant variety, e.g., Pant Composite-1.
iv. Treat the seeds with Bavistin (carbendezim) 0.05%.
v. Spray the crop with Indofil M-45 or Blitox at 0.2% (2 kg/ha) at 15 days interval.