Agriculture Farming

How to Control Pests and Diseases in Mustard Crop: Causes, Symptoms, Chemical, and Biological Management

By: Jagdish Reddy
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Mustard is an annual herbaceous plant of the Brassicaceae family that is cultivated for its seeds, which are used as a spice. Yellow flowers adorn mustard plants, which are thin herbaceous herbs. The plant leaves are toothed, lobed, and occasionally have larger terminal lobes. Plants can reach 16 cm in length. The yellow flowers grow in spike-like clusters of 2 to 12, and individual flowers are 8 mm in diameter. The seeds are red to brown and are produced from each flower. 

How to Control Pests and Diseases in Mustard Crop

Mustard can grow 1.2 to 2 m in height and survives only one growing season as an annual plant. It is believed that mustard originated in Europe’s temperate regions, which can be called brown mustard, red mustard, yellow mustard, or wedlock. If you plan to cultivate mustard, you must know that the diseases and pests discussed below significantly affect mustard crop yield and quality.

How to control pests and diseases in Mustard crop

Diseases in Mustard crop

Alternaria blight

Two species of Alternaria, Alternaria brassicicola And Alternaria brassicae, attack a mustard crop, and it is also called “Leaf spot” or “Black leaf spot” disease. It caused seed yield loss of up to 35% in mustard. In addition to damaging fresh crops, this infection can also damage stored crops. These pathogens are transmitted primarily by seeds with mycelium or spores underneath or on the seed coat.

Aside from water, wind, animals, and infected tools, spores may also be spread by water, wind, and animals. Most infections result from leftover infected crops on the ground after harvest. Also, perennial plants, vulnerable weeds, and crop debris can harbor this phytopathogen dormant.

Disease symptoms
  • The disease will attack the lower leaves as small circular brown necrotic spots slowly increase in size.
  • In severe cases, many concentric spots coalesce to cover large patches showing brightening and defoliation.
  • Also affected are stems and pods, which develop circular to linear, dark brown lesions.
  • Seeds from infected pods are small, discolored, and shriveled.
Chemical control and management methods
  • Mustard varieties such as Pusa Kranti and Seeta var are resistant to disease. It is also recommended to grow multiple disease-resistant varieties of Indian mustard, like DIR-157 & DIR-1522, that are resistant to Alternaria blight, white rust, powdery mildew, and downy mildew.
  • The use of healthy seeds for sowing should be preferred.
  • Spray Mancozeb 75 WP at the rate of 2 kg in 1000 liters of water per hectare at ten days intervals as soon as the symptoms appear on the plants.
  • Collect and burn the affected plant portions after the harvest of the crop.

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White rust

Albugo candida causes this disease, also called “White Blisters of Crucifers.” In severe conditions, it caused yield losses of up to 55% in late-sown crops. Other crucifers hosts are Radish, Tumip, Cabbage, Cauliflower, Taramira, Spinach & sweet potato (non-crucifers). A rusty white appearance is caused by white creamy pustules and sporangia exposing powdery masses of spores on infected surfaces; that’s why it’s called white rust. Stag heads are also produced on floral parts due to systemic infection. 

Disease symptoms
  • Both local and systemic infections are observed.
  • In case of local infection, white creamy yellow raised bumps appear on the leaves, which later merge to form patches.
  • Mixed infections of white rust and downy mildew cause swelling and distortion of the stem and floral parts in humid weather and develop “stag heads” due to hypertrophy and hyperplasia.
Chemical control and management methods
  • Use healthy & clean seeds or certified seeds.
  • Destroy weeds in & around the field.
  • Collect & destroy infected plant parts.
  • Follow long crop rotation with non-host crops.
  • Treat the seeds with Metalaxyl at 6 grams per kg, which protect for 60 days, or mancozeb 92.5 g per kg seed.
  • Spray the crop with Bordeaux mixture 0.8% or mancozeb 0.25% at ten days intervals.
  • Use recent fungicides like fosetyl-Al. It has both apoplastic (through the xylem) & symplastic (through the phloem) movement. So, this is an Ambimobile fungicide.
Downy mildew

Peronospora parasitica causes this disease, which can affect plants at any stage of development, including seedlings, cotyledons, and harvest. As an obligate parasite, the fungus reproduces by forming oospores inside host tissues and on host plants. Wind-borne sporangia also cause secondary spread.

Disease symptoms
  • Grayish-white irregular necrotic patches develop on the lower surface of leaves.
  • Later under favorable conditions, brownish-white fungal growth may also be seen on the spots.
  • The most conspicuous and pronounced symptom is inflorescence infection, causing hypertrophy of the peduncle of inflorescence and developing stag head structure.
  • All aerial parts of the plant exhibit symptoms, but leaves and inflorescences are most prominent.
Chemical control and management methods
  • Infected plant debris can be collected and destroyed, crops can be rotated with non-host crops, and seeds can be sown early in the season to control the disease to a certain extent.
  • The disease can be managed chemically by treating seeds with 6g/kg Metalaxyl followed by spraying 0.2% Metalaxyl.
  • Spray the crop with 0.2 % Ridomil or 0.1% Karathane as soon as the symptoms are noticed, and repeat the spray two to three times at ten days intervals.

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Powdery mildew

Powdery mildew, a worldwide plant disease, causes a powdery growth on the surface of leaves, buds, young shoots, fruits, and flowers. Erysiphe cruciferarum is responsible for this disease. The disease affects all parts of the plant above the ground. The white powdery appearance is due to large microscopic spores borne in chains.

The fungus is ectophytic and spreads on the leaf’s surface, sending haustoria into the epidermal cells. In addition, wind-borne conidia spread the disease. This disease is favored by dry climates and gets severe in inundated conditions.

Disease symptoms
  • Powdery mildew fungi produce structures inserted into plant cells, allowing them to extract nutrients required for development and spore production. 
  • Symptoms appear as dirty white, circular, floury patches on either side of the leaves.
  • Under favorable environmental conditions, entire leaves, stems, floral parts, and pods are affected.
  • The whole leaf may be covered with a powdery mass.
Chemical control and management methods
  • Agricultural practices like the collection and destruction of infected plant debris are helpful in the management of this disease.
  • Water plants early in the morning to allow them to dry during the day. Watering with drip irrigation and using soaker hoses will keep foliage dry.
  • Use a slow-release, organic fertilizer on crops and avoid excess nitrogen. Soft, leafy, new growth is most susceptible
  • The disease can be managed by applying sulfur dust at 30kg/ha or by spraying 2g wettable sulfur or 1 ml dinocap, or 1 ml tridemorph per liter of water.
Bacterial blight/ black rot

Most crucifer crops can be affected by black rot, caused by the bacteria Xanthomonas campestris pv campestris. The disease is difficult to manage for growers and is considered the most severe disease of crucifer crops worldwide. If warm, humid conditions follow periods of rainy weather during early crop development, the disease can cause significant yield losses. Furthermore, late infections can allow other rot organisms to enter and cause significant damage during storage.

Disease symptoms
  • The leaf tissue turns yellow, and chlorosis reaches the leaf’s center, forming a V-shaped area with a base of V towards the midrib. The veins show brown to black discoloration. 
  • Dark-colored streaks are formed on the stem from the ground level; gradually, these streaks enlarge and wrap around the stem.
  • The stem becomes hollow due to internal rotting.
  • Midrib cracking of lower leaves, browning of veins, and withering are observed.
  • In severe cases, the vesicular bundles of the stem also turn brown, and the plant collapses.
Chemical control and management methods
  • Seed treatment with mercuric chloride for half an hour effectively eradicates seed-borne infection.
  • A hot water bath for 30 minutes at 50 °C is the recommended treatment to sterilize the seeding material. It is not 100 percent effective against black rot but considerably reduces the disease’s incidence. The drawback is that it might lower the germination rate.
  • Seed treatments with hot water are very effective in blocking the contamination of fields. Foliar treatments with copper-based fungicides every seven to ten days can also slow the spread of the disease. 
  • A three-year rotation of the crop is desirable.
  • Strict sanitary precautions should be maintained.

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Club root

Plasmodiophora brassicae is a soilborne fungus that causes clubroot in mustards and related crucifers. Unlike most fungi, it does not form mycelia and is an obligate parasite, meaning it can only develop and multiply in living cells. The vegetative phase consists of a multinucleate mass of protoplasm without a cell wall.

Even though the organism primarily attacks members of the Cruciferae, different crops cause the disease to be more intense. In addition to the specialized forms, the organism exists in many different races, explaining the variation in resistance and ability to survive in different environments.

Disease symptoms
  • The first signs of clubroot are abnormal wilting and yellowing of leaves, especially on warm days.
  • When infection occurs at an early stage of growth, young plants are stunted and may die, whereas infected plants fail to form marketable heads.
  • Diseased plants usually have swollen and distorted roots when they are pulled from the soil
  • Leaves turn pale green or yellow, followed by wilting, and under severe conditions, the plants die.
  • Root malformation may vary from small swellings on the tap and lateral roots to large club-shaped roots, depending on when the plants became infected.
Chemical control and management methods
  • The only organic control available is to raise the pH of the soil to a more alkaline 7.2 by mixing oyster shells or dolomite lime into the soil in the fall (small gardeners and farmers). Simple and affordable soil test kits are available to check pH often.
  • Soil fumigation is not recommended because they are not 100 percent effective. However, adding limestone (calcium carbonate CaC03) and hydrated lime (calcium hydroxide Ca(OH)2) before planting will reduce the incidence of the disease by raising the pH (7.2).
Sclerotinia stem rot

The fungus Sclerotinia sclerotiorum causes Sclerotinia stem rot, also known as white mold. Sclerotia are hard dark structures that the fungus forms from year to year. Sclerotia are shaped bodies of tightly packed white mycelium covered in a dark, melanized coating. Saturated soils and a full canopy favorably influence the emergence of apothecia from the sclerotia. A mushroom-like body produces millions of airborne spores almost daily over seven to ten days. During favorable weather conditions, these spores are released and can travel to other fields.

Disease symptoms
  • Elongated water-soaked lesions appear on the stem near the crown region, later covered with cottony mycelial growth.
  • The plant looks whitish from a distance at the internodes or base.
  • Premature ripening and shredding of stem, wilting, and drying.
  • Brown to black sclerotial bodies may also be seen on infected plant parts.
Chemical control and management methods
  • The spores of Coniothyrium minitans or Trichoderma species have been applied to soils to reduce the fungal load of Sclerotinia and hinder disease development.
  • Applications of foliar fungicides are recommended only in fields with severe disease development. Depending on the crop and its developmental stage, treatment will differ. However, fungicides based on iprodione or copper oxychloride (3 g/l of water) effectively control these fungi. Unfortunately, it has been reported that some of these compounds are prone to developing resistance.

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Mustard Flowering

Pests in Mustard crop

Mustard aphid

The mustard aphid is a severe pest of mustard in India and other tropical regions worldwide. The population dynamics of this species are considerably influenced by immigrant alate, which migrates to the mustard crop from the off-season shelter. Aphids reproduce at a higher rate in the early vegetative stage of mustard plants, when the developmental period is shortest, and the production of winged morphs is lowest.

Damage symptoms
  • Nymphs and adults suck leaves, buds, and pods.
  • Infested leaves can curl, and at an advanced stage, the plant may wither and die.
  • As a result, plants remain stunted and sooty mold grows on the honeydew excreted by insects.
Biological control
  • Conserve the following natural enemies: ladybird beetles are the most efficient mustard aphid predators. An adult beetle may feed on an average of 10-15 adults per day.
  • Several entomogenous fungi, including Cephalosporium spp., Entomophthora, and Verticillium lecanii infect aphids
  • The lacewing, Chrysoperla carnea, predates the mustard aphid colony
  • In February and March, the predatory bird Motacilla cospica is actively feeding on aphids
Chemical control
  • Spray the crop with oxy-dematon methyl 25 EC (1 ml / l) or dimethoate 30 EC (1 ml / l), or thiamethoxam 25 WG (0.2 g/l). If the population builds up again, repeat the spray at 15-day intervals or follow agro-advisory and aphid forecasts to schedule insecticide spray.
Painted bug

Pests such as the painted bug are serious problems for mustard. In addition to adults, nymphs also cause damage. Nymphs are about 4mm long and 2.66mm wide when fully grown. There are many brown markings on their black bodies. An adult bug will measure about 3.71 mm in length and 3.33 mm in width. They are sub-ovate, black, and have several orange or brown spots.  

Damage symptoms
  • Adults and nymphs suck all parts of the plant.
  • The attack causes young plants to wilt and wither.
  • A resinous substance excreted by adult bugs spoils pods.
  • The yield quality and quantity (31% losses) are affected when grown-up plants are infected.
  • Harvested crop on the threshing floor is also infested.
Biological control
  • Conserve bio-control agents such as Alophora spp. (tachinid fl y) parasitizing eggs of painted bugs.
  • Burn the remains of the mustard crop so that the stages of the insect do not reach the following year’s crop.
  • The bugs usually congregate on the leaves and stem, which can be jerked to dislodge them and killed in kerosene water
Chemical control
  • Spray one liter of malathion 50 EC or 625 ml of endosulfan 35 EC or quinalphos 25 EC in 150-200 liters of water per ha.
  • The pest can also be controlled by spraying the crop with oxy-demeton methyl (0.025%) or permethrin (0.008%) or fenvalerate (0.01%) or deltamethrin (0.0028%) or dimethoate (0.03%).
Mustard sawfly

Adults are orange-bodied with smoky transparent wings. The pest is active during the crop’s seedling stage, i.e., October – November. The larva is greenish-black with a wrinkled body and eight pairs of pro-legs. On the slightest touch, the larva falls to round and feigns death. The larvae had six instars, fed on the leaves, and pupated after 14-16 days.

Damage symptoms
  • Initially, the larva nibbles leave and feed on the midrib from the margins.
  • In addition to causing numerous shotholes, the grubs also riddle the leaves with their voracious appetite.
  • Seedlings and older plants fail to produce seeds when they devour the epidermis of the shoot.
  • It is estimated that this pest results in yield losses of up to 18%. At the seedling stage, severe cases require resowing the crops.
Biological control
  • Hand-picking the grubs early in the morning has been useful in controlling the population of the grubs.
  • Parasitoids: Perilissus cingulator ( larvae)
  • Entomopathogen: Bacterium Serratia marcescens

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Mustard Farm
Chemical control
  • Bt formulations at 0.05- 0.2 percent exhibit excellent control 
  • Spray the crop with malathion 50 EC at 1000 ml/ha and quinolphos 25 EC at 625ml/ha. All this should be applied in about 600 to 700 liters per ha.
  • Dusting the 2% Methyl Parathion dust at the rate of 20-25 kg per hectare controls the pest effectively
Larger moth (leaf Webber)

During the larval stage of Crocidolomia binotalis, the damage is caused. Larvae rarely attack seedlings, which feed on plants at all stages. At first, they look pale green, but shortly before hatching, they turn a bright yellow and brown color. A newly hatched caterpillar larva is about 2 mm long and matures to 20 mm long with long hairs.

Eventually, they make thick webs over the leaves, and the caterpillars feed beneath them. From the early stages of the crop to harvest, moths can infest it. They are usually active at night. Other crucifers such as radish, turnip, and cabbage are also affected.

Damage symptoms
  • In the early stages of life, larvae feed on the chlorophyll of young leaves, and as they grow older, they eat older leaves, buds, and pods. Finally, they make webbings and live within them.
  • Defoliation occurs on severely attacked plants.
  • There is no seed in the pods because they are eaten away.
Biological control
  • The pest is regulated by two larval parasitoids viz., Microbracon mellus and Apanteles crocidolmiae
Chemical control
  • Spray fenvalerate 20 EC or cypermethrin 10 EC or deltamethrin 28 EC 250 ml, cartap hydrochloride 50 SP 500 ml, 
  • Alternatively, spinosad 45 SC 125 ml/ha or azadirachtin 0.03% 2.5-5.0 L/ha can be spayed for control over leaf Webber. 

Conclusion

Mustard is susceptible to several diseases. The incidence of these diseases varies yearly, but it is more prevalent in years with wetter than normal conditions. Along with diseases, pests also significantly affect the mustard crop yield. Therefore, keep a close eye on above discussed major pests and diseases to save your crop from infections at the early stages.

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