Wheat Disease

Wheat Disease

Powdery mildew Wheat Disease

Powdery mildew is caused by Blumeria graminis f. sp. tritici 

Disease symptoms(Wheat Disease)

• Powdery mildew can easily be diagnosed by the white, powdery patches that form on the upper surface of leaves and stem.
• Greyish white powdery growth appears on the leaf, sheath, stem and floral parts.
• Powdery growth later become black lesion and cause drying of leaves and other parts.
• The disease infects plants during periods of high humidity (not necessarily rain) and cool to moderate temperatures (20-21°C).

Disease Cycle. Fall infections of newly planted wheat occur when spores develop on volunteer wheat or within cleistothecia. The powdery mildew fungus overwinters as cleistothecia on plant debris or as mycelium on infected plants. Conidia form on infected winter wheat plants and serve as the primary means of inoculum. Conidia are wind dispersed and germinate under cool, humid conditions. Under favorable conditions the disease can complete a life cycle in 7 to 10 days. Development ceases at around 77°F (25°C).

HOW TO CONTROL POWDERY MILDEW Wheat Disease

• Rubbing the infected leaves together can help partially remove the disease from your plants.
• Remove all the infected plant parts and destroy them. Remember, do not compost any infected plant, as the disease can still be spread by the wind.
• Spray infected plants with fungicides. Effective fungicides for powdery mildew treatments or cures include sulfur, lime-sulfur, neem oil, and potassium bicarbonate.

PREVENT POWDERY MILDEW(Wheat Disease)

• Choose plants that are resistant or tolerant to powdery mildew.
• Powdery mildew thrives in hot and humid weather, so avoid overhead watering to reduce humidity. Also selectively prune overcrowded areas to increase air circulation; this also helps reduce humidity for your plants.
• Spray your plants with fungicides according to their directions. If you don’t want to use fungicides, try spraying your plants with a solution of 1 teaspoon baking soda in 1 quart of water. Remember to spray your plants thoroughly.

Loose smut Wheat Disease

Loose smut is caused by Ustilago tritici

Disease symptoms Wheat Disease

• It is a seed borne disease; infection occurs during Loose Smut flowering through wind-borne spores.
• The infection remains dormant inside the otherwise healthy looking seed but the plants grown from such seeds bear infected inflorescence.
• At this time, infected heads emerge earlier than normal heads. The entire inflorescence is commonly affected and appears as a mass of olive-black spores, initially covered by a thin gray membrane.
• Once the membrane ruptures, the head appears powdery.

Disease Cycle . Loose smut is a seed and wind-borne fungal disease. The pathogen survives in the wheat seed until germination and then grows up the shoot and infects the head. Healthy wheat plants can be infected during the first two days of flowering by wind-borne spores from infected plants. Rain and insects can also help spread the fungus. Humid weather, including light rain and heavy dew, and cool to moderate temperatures, between 60 and 71°F (16-22°C), promote infection. When spores land on healthy flowers, they germinate and become dormant within the ovary until seeds germinate. Yield loss is in direct proportion to the number of smutted heads present.

Cultural control Wheat Disease

• Plant certified smut-free seed. Do not use seed wheat from fields with loose smut.
• Use resistant cultivars.
• Seedborne inoculum can be destroyed with hot water treatments.

Chemical control Seed treatment with a systemic chemical controls the disease.

• Baytan 30 at 0.75 fl oz/100 lb seed plus a dye. Not registered for use in WA. See label for reentry restrictions.
• Charter at 3.1 fl oz/100 lb seed plus a dye. See label for rotation and reentry restrictions.

Brown rust Wheat Disease

disease of wheat caused by the fungus Puccinia recondita f. sp. tritici.

Disease symptoms Of This Wheat Disease

• The most common site for symptoms is on upper leaf blades, however, sheaths, glumes and awns may occasionally become infected and exhibit symptoms.
• The pustules are circular or slightly elliptical, smaller than those of stem rust, usually do not coalesce, and contain masses of orange to orange-brown Urediospores.
• Leaf rust pustules form on infected wheat and are small (.04-.08 mm in length), reddish-orange oval fruiting bodies (uredinia) on the leaf surface .
• Pustules can be either scattered or clustered. Each pustule contains thousands of orange, powdery rust spores that rupture the epidermis of the leaf surface as the fungus matures and then are disseminated by the wind and rain.
• Pustules are usually surrounded by orange dust, and sometimes also a narrow, yellow or white border or “halo” . Unlike other rusts, the orange spores will rub off of your finger and, if infection is severe, field scouts may find the orange dust on their hands and clothing.
• As plants mature, pustules begin producing black spores. These pustules resemble tar spots and are most noticeable on lower leaves and leaf sheaths. Orange spots (not pustules) may also form on the heads and culms of diseased plants. Leaf rust, unlike stem rust, does not form pustules on these organs.

Disease Cycle. The severity of leaf rust is affected by the growth stage at the time of infection, weather conditions, and the amount of rust inoculum present. Damage is greater when plants are infected before flowering, especially when the flag leaf becomes infected. Late-maturing varieties of wheat and cool (60-75°F or 16-24°C), wet weather, including rain and dew, also promote the disease. However, heavy rain washes spores off of the plant, and dry, windy conditions favor spore dispersal. Losses due to leaf rust are caused by a reduced number of kernels per head, reduced size of kernels, lowered test weights, and reduced protein content of the grain.

Stripe rust /Yellow rust(Wheat Disease)

Stripe rust is caused by the fungus Puccinia striiformis.

Disease symptoms of this Wheat Disease

• Mainly occur on leaves than the leaf sheaths and stem. Bright yellow pustules (Uredia) appear on leaves at early stage of crop and pustules are arranged in linear rows as stripes.
• The stripes are yellow to orange yellow. The teliospores are also arranged in long stripes and are dull black in colour.
• The pustules of stripe rust, which, contain yellow to orange-yellow urediospores, usually form narrow stripes on the leaves.
• Pustules also can be found on leaf sheaths, necks, and glumes.

Disease Cycle. Stripe rust develops in cooler temperatures (55-75°F or 13-24°C) than other rust diseases, allowing it to develop earlier in the season. Stripe rust develops most rapidly between 50 and 60°F (10-16°C), and development slows when temperatures exceed 75°F (24°C). Cool, wet falls, mild, open winters, and long, cool, and wet springs all promote disease development.

Stripe rust over-summers on volunteer wheat and perennial grasses. It also develops in the fall and winter in the southern United States, and then spores are carried north into the central Great Plains in the spring. The fungus can persist through cold climates (as low as 23°F or -5°C), overwintering on wheat and grassy weeds or as dormant mycelium under snow cover.

Black rust Wheat Disease

Stem rust, caused by the fungus Puccinia graminis f. sp. tritici,

Disease symptoms of this Wheat Disease

• Symptoms are produced on almost all aerial parts of the wheat plant but are most common on stem, leaf sheaths and upper and lower leaf surfaces.
• Pustules (containing masses of urediospores) are dark reddish brown – occur on both sides of the leaves, on the stems, and on the spikes.
• Pustules are usually separate and scattered, heavy infections -coalesce.
• Prior to pustule formation, “flecks” may appear. Before the spore masses break through the epidermis, the infection sites feel rough to the touch.
• As the spore masses break through, the surface tissues take on a ragged and torn appearance.

Disease Cycle. The stem rust fungus requires two hosts to complete its life cycle. Telial stage hosts include wheat, barley, and several grasses, and aecial hosts, or alternate hosts, include European barberry such as Berberis vulgaris (Figure 9.27a & b), B. fendleri, and B. canadensis.

The fungus overwinters as teliospores on plant residue (Figure 9.28) or in the soil in colder climates and as urediospores on winter wheat grown in warmer climates. Wind-borne urediospores from southern states are the primary inoculum for disease in the Great Plains. Diseased plants produce more urediospores, creating a second inoculums.

Stem rust occurs worldwide, and is especially important in areas exhibiting warm, humid conditions (65-85°F or 18-29°C). Losses tend to be greatest when severe infection occurs before grain fill. Diseased plants produce shriveled grain and lodging results in loss of spikes.

CONTROL AND PREVENTION of this Wheat Disease

Flag smut Wheat Disease

Disease symptoms Wheat Disease

• Symptoms can be seen on stem, clum and leaves from late seedling stage to maturity.
• The seedling infection leads to twisting and drooping of leaves followed by withering.
• Grey to grayish black sori occurs on leaf blade and sheath. The sorus contains black powdery mass of spores.

Soil or seed borne spores infect the new wheat plant before emergence. Infection is favoured by early sowing into relatively dry and warm soils. Optimal temperature for infection is 20°C, but infection may occur at as low as 5°C and as high as 28°C. The fungus grows inter and intra cellularly between vascular bundles of the leaf tissue and other effected plant parts.

Cultural control Wheat Disease

• Resistant cultivars are available.
• Rotate 2 years out of winter wheat.
• Plant seed shallow (less than 1 inch) when soils cool in fall.

Chemical control Seed treatment is effective against seedborne and soilborne inoculum.

• Baytan 30 at 0.75 fl oz/100 lb seed plus a dye. Not registered for use in WA. See label for reentry restrictions.
• Dividend Extreme at 2 to 4 fl oz/100 lb of winter wheat or triticale seed and at 4 fl oz/100 lb of spring wheat. Do not graze green forage for 55 days after planting. Do not plant any crop other than wheat within 30 days in fields in which treated seeds were planted. See label for reentry restrictions.

Hill bunt or Stinking smut Wheat Disease

Disease symptoms of this Wheat Disease

• The fungus attacks seedling of 8-10 days old and become systemic and grows along the tip of shoot.
• At the time of flowering hyphae concentrate in the inflorescence and spikelets and transforming the ovary into smut sorus of dark green color with masses of chlamydospores.
• The diseased plants mature earlier and all the spikelets are affected.

Life cycle
The spores on the seed surface germinate along with the seed. Each produces a short fungal thread terminating in a cluster of elongated cells. These then produce secondary spores which infect the coleoptiles of the young seedlings before the emergence of the first true leaves. The mycelium grows internally within the shoot infecting the developing ear. Affected plants develop apparently normally until the ear emerges when it can be seen that grain sites have been replaced by bunt balls. In India disease occurs only in Northern hills, where wheat is grown.

Management of this Wheat Disease

• Treat the seeds with carboxin or carbendazim at 2g/kg.
• Grow the crop during high temperature period.
• Adopt shallow sowing.
• Grow resistant varieties like Kalyan sona, S227, PV18, HD2021, HD4513 and HD4519.

Karnal bunt Wheat Disease 

Disease symptoms of this Wheat Disease

• Symptoms of Karnal bunt are often difficult to distinguish in the field due to the fact that incidence of infected kernels on a given head is low.
• There may be some spreading of the glumes due to sorus production but it is not as extensive as that observed with common bunt.
• Symptoms are most readily detected on seed after harvest.

Karnal bunt was reported as a soil borne disease by Mitra (1931), but now it is considered as an air borne disease. The fungal spores are also transferred by means of equipment, tools or by man moving from milling places. The spores remain viable for several years in soil (Bonde et al. 2004), wheat straw and farm yard manure. Soil or seeds are primary sources of inoculum. Environment plays a key role in disease progression. Teliospores germinate at suitable temperature (15–25oC) and humidity in the soil. This condition generally dominates during February to March in North Indian plains.

Control measures of this Wheat Disease

Sowing crops at night time.

• Seed treatment with Vitavax@2.5gm/kg seed
• Avoid excess irrigation at flowering time
• In crop meant for seed ,spray the crop with Indofil M-45@2.5kg/ha or Tilt @500 ml /ha in 1000 litres of water at ear emergence stage.

Leaf blight(Wheat Disease)

Disease symptoms(Wheat Disease)

• Reddish brown oval spots appear on young seedlings with bright yellow margin. In severe cases, several spots coalesce to cause drying of leaves.
• It is a complex disease, having association of A. triticina, B. sorokiniana and A. alternate.

Life Cycle

Many forms of bacterial leaf blight are seedborne, and are able to survive for long periods of time in this way. The bacteria are also able to survive in plant debris, but not in soil alone. Seed allows for the spread of bacteria, while rain and sprinkler irrigation helps the disease develop further. Wet conditions and splashing water distribute bacteria amongst surrounding plants. Bacteria will initially appear in the mid to upper parts of the canopy, and then it will spread throughout the plant, possibly affecting leaves, pods, and fruits. The disease will likely be seen early on in the season while seedlings are beginning to develop. Once infected, the bacteria will affect all growth stages of the plant. In many cases, premature defoliation will occur, leaving the plants’ fruit vulnerable to direct sunlight. Ultimately, this can lead to substantial yield loss, so long as the bacteria are able to fully occupy the plant.

Chemical control(Wheat Disease)

• Seed treatment with 0.1 g Streptocycline and 0.1 g Copper Sulfate or 0.3 g Agrimycin-100 and 0.1 g Copper Oxychloride in one liter of water for 20 minutes
• Foliar spray of 0.05 g Streptocycline and 0.05 g Copper Sulfate 

Foot rot(Wheat Disease)

foot rot caused by Fusarium spp

Disease symptoms(Wheat Disease)

• The disease mainly occurs in seedlings and roots and rootlets become brown in colour.
• Seedlings become pale green and have stunted growth.
• Fungus produces sporangia and zoospores and oospores.

Life cycle

The fungi that cause root, foot, and crown rots are primarily soil- and residue-borne. Plants get infected early in the season as roots pass through the soil. Bipolaris sorokinianainfection is more common when seedlings are stressed by drought, high temperatures, freezing or flooding conditions. Fusarium spp. in addition to being residue- and soil-borne, can also survive on seed. The take-all pathogen also survives in the soil and plant debris and infection is favored by neutral to alkaline soil pH conditions.

Management(Wheat Disease)

• Zinc sulfate (10% solution = 16 pounds in 20 gallons of water) is perhaps the most effective and least toxic of the two baths. 
• Copper sulfate (bluestone) solutions (10% solution = 16 pounds in 20 gallons of water) are also useful but are toxic if consumed by the sheep. 

Head scab/ Fusarium leaf blotch (Snow Mold)(Wheat Disease)

PATHOGEN: Fusarium graminearum (anamorph)

Disease symptoms(Wheat Disease)

Leaf blotch

• The blotching caused by this organism becomes evident on leaves at about late-joint to early-boot growth stage.
• Young lesions occur as oval to elliptical, greyish green mottled areas, usually located where the leaf bends. The lesions enlarge rapidly, developing into large, “eyespot” blotches with bleached or light grey centers; the leaves tend to split or shred, beginning at the centers of the lesions.
• The fungus also can cause head scab.
• Symptoms of Fusarium head blight include tan or light brown lesions encompassing one or more spikelets. Some diseased spikelets may have a dark brown discoloration at the base and an orange fungal mass along the lower portion of the glume.
• Grain from plants infected by Fusarium head blight is often shriveled and has a white chalky appearance.
• Some kernels may have a pink discoloration.
• Infected florets (especially the outer glumes) become slightly darkened and oily in appearance.

The disease cycle

Fusarium graminearum overwinters on infested crop residues (corn stalks, wheat straw, and other host plants) (Figure 12). On infested residues, the fungus produces asexual spores (macroconidia) which are dispersed to plants and other plant debris by rain-splash or wind. When conditions are warm, humid, and wet, the sexual stage of the fungus (Gibberella zeae) develops on the infested plant debris. Bluish-black perithecia form on the surface of these residues, and forcibly discharge sexual spores (ascospores) into the air (Figure 13). The ascospores are picked up by turbulent wind currents and may travel great distances in the air.

Disease Management(Wheat Disease)

• Plant healthy, high germ seed
• Crop rotation to a broadleaf crop
• Withhold irrigation prior to and during flowering, which can extend up to 7-10 days
• Incorporate cereal straw or corn stubble to accelerate degradation and inoculum destruction.
• Foliar spray must be applied at the first sign of anthers extruding from the head to protect the flowers for 7-10 days.

Helminthosporium leaf blotch (Spot Blotch)(Wheat Disease)

Disease symptoms(Wheat Disease)

• Lesions caused by this disease are elongated to oval in shape and are generally a dark brown color.
• As lesions mature, the centers often turn a light brown to tan color, surrounded by an irregular dark brown ring (21 on leaf; 22 on spike).
• Primary infections tend to be on the lower leaves, beginning as chlorotic flecks or spots. These infection sites enlarge, turn dark brown, and often coalesce. When the disease is severe, affected leaves or leaf sheaths may die prematurely.

Life Cycle

Although spot blotch is often a seedborne disease, primary infections can also be initiated from inoculum surviving on crop residues, collateral hosts (e.g. rice, barley and other grasses) or conidia in the soil. The fungus can survive on straw or in the soil for several months, after which its viability begins to decline. It has been shown that the conidia found on wheat straw tend to aggregate into clumps after storage for 5 months. Although the sexual state of this fungus (C. sativus) is known (see later), it is not a source for infection, leaving conidia as the major vehicle for dispersal and survival of the pathogen.

Management(Wheat Disease)

• Allow one or preferably a two-year break between susceptible crops.
• If available, use varieties which have some resistance.
• Burying residue may reduce disease incidence. Foliar-applied fungicides will reduce losses

Seedling blight(Wheat Disease)

Disease symptoms(Wheat Disease)

• This symptom is seen when ears become infected during the early flowering stages. Later infections may result in infection of the grain but without obvious bleaching of the ears.
• Fusarium lesions often begin in the leaf sheath at the stem base where crown roots split the leaf sheath when emerging. This infection can then spread up the leaf sheath causing long dark brown streaks at the stem base
• The ear blight phase of the disease can cause yield loss but is most important as it can result in mycotoxin production in the grain.

Life Cycle

 seedlings (post-emergence damping-off or seedling blight) that can be caused by many fungi, primarily Pythium spp., Phytophthora spp., Fusarium spp., Rhizoctonia spp., and perhaps others. These fungi are common inhabitants in soils worldwide and have a broad host range. They survive between crops as dormant resting structures (oospores, sclerotia), in crop debris, saprophytically, and pathogenically on weeds and other hosts.

Disease Management(Wheat Disease)

• Management options are generally the same for all corn seedling diseases. Wet and cool soil temperatures (less than 50° to 55° F) can delay seed germination and emergence and predispose corn seedlings to disease.
•   Seedlings become more susceptible to infection the longer a seed is in the ground before emergence and the more stress germinating corn endures.  Be sure to plant high quality seed at the appropriate planting depth and soil conditions to promote rapid germination and emergence. 
• Fields that have good drainage and warm quickly should be targeted for earlier planting.  Fields that have a tendency to stay wet or have a history of seedling disease should be planted slightly later in the season when soil temperatures are more favorable for germination. 
• Avoid mechanical injury to the seed and herbicide injury, as these stresses may influence the occurrence of seedling diseases.