Disease of field crops

Disease of field crop in agriculture plant pathology

1. Assignment PLP-302 Diseases of field crops

2. 1-Loose smut of wheat Symptoms: All grain in spikes also be damage and infected Symptoms appear in maturity All grains are converted into black powdery masses Hard covering of grain is converted into very thin papery membrane Starching part of grain convert into black masses Trillion of spores produced in one spike

3. Causal organism: Ustilago Tritici Disease cycle: Fungus entirely seed borne. Primary infection is the source of first infection by infected seed and debris Secondary infection is the result of primary infection and the asexual spores are produced and spread by wind.

4. Spore shape:

5. 2-Coversmut of wheat Symptoms: Pericarp remain intact Grain converted into black powdery masses All grain in spikes are not effected only few grains effected and convert into black powdery masses Hard, thin and black The effected grain large in size than healthy grain

6. Disease cycle:

7. 3-Ergot of rye Symptoms: t he ovary of cereal and grass plants. no other part of the plant is infected. The infected ovary is replaced by a purplish black sclerotium, commonly ref erred t o as an ergot Size of the sclerotium is host plant dependent . They are generally 1 t o 5 times larger than the host seed the largest ergots (1­5 cm, 0. 5­2 in) are found in large seeded plants such as cereal rye

8. spores

9. Causal organism: Clavicep s purpurea Disease cycle:

10. 4- Karnal Bunt of wheat Introduction: First time reported from India in 1931 Karnal district of India and in Pakistan it’s reported in 1952 by the shipment of seed from India and spread throughout the Punjab. The incidence is 30% from Gujrat and Sargodha and also reported from the dry areas of Punjab i : e Multan and Rahim yar khan. Symptoms: Symptoms are not prominent during early growth stages of plants. They appear at the time of heading when more green ears are emerged. Few grain irregularly effected in the ear converted into black powdery mass enclosed by the pericarp . Not all the grains in a stool carry the disease and even in the same ear only few grains are smutted. Since the embryo is not always damaged such partially affected grains can germinate and even produce a healthy plants

11. casual organism: Disease cycle: Fungus survive in the soil as teliospores and remains viable for years. At the time of harvesting and threshing the teliospores dispersed and cause contamination. By the sowing of infected seeds the contaminated seedlings produced than the teliospores present in the soil germinate and produce single spore which cause the infection. Neovossia indica

12. Life cyle :

13. Management: Resistance verities Crop rotation with fodder crops 5- Downy mildew of maize This disease is reported from India Pakistan and other parts of the world casual organism: Sclerospora sorghai ,

14. Symptoms: Sorghai produce white streaks narrow long along the entire length of the leave. When the intensity of the disease increases these stripes coalesce and form whitish yellow patches. In some cases as a result of secondary infection the streaks are short and narrow not on entire length. The number of stripes coalesce and margin loss to form patches. The downy growth of fungus appears on both sides of leaves and lateral stages. There is browning of tissue, Pickering of young leaves also noticed. Wearing cholorotic stripes. Necrosis and cholorisis at lateral growth not on early growth. The major damage of downy mildew is complete loss of the plant in early growth stages. Varying degree of number of grains losses during formation of cobs with varying infection. Disease cycle : Oospores survive in the soil and remain in plant debris. It’s a soil borne fungus. It’s viable when next season and produce unicellular conidia spores and cause infection and then secondary infection is due to production of conidiophores and in one growing season they form several successive generations. . The loss of viability at temperature 25 C and 90% relative humidity. Germination is essential for the formation of conidia and moisture and night hours are important

15. Management: Planting of resistance verities. Destruction of alternate host and other crops. Use of fungicides like M-45 after 10 days sowing of crops with 7 days interval is recommended. It can be controlled 100% with seed treatment with Ridomil MZ75 (wet able powder)@4g/kg of seed. 6- Powdery Mildew of Cereals   The symptoms of this disease is very much alike in all type of cereals. The fungus growth appears on the upper surface of the leaf. The fungus develops numerous superficial colonies. The mycelium forms flocculent growth at first white when conidia are formed the color will change into the grey to reddish brown when cleistothecia are produce. Infected plants remains stunted due to reduction in size and number of leaves. Symptoms:

16. casual organism: Blumeria graminis Disease cycle: The fungus is soil borne in the form of cleistothecia (it can survive in 13 years at low temperature. The ascospores best germinate at 16-20 C but the optimum temperature for conidial growth is 15 C. Cultivation of mix verities delay and reduce the chance of powdery mildew Management: Treatment of crops stubble is recommended. Use of systematic fungicides like vitavex but use triazole fungicides. Payten and baliton @0.1-0.2% for 100% control

17. 7- RATOON STUNTING OF SUGARCANE Symptoms: Diseased stool (single plant) stunted growth, reduce tillering and internodel length is reduce. Stunting of canes with yellow leaves. These symptoms may be due to nutritional deficiencies or may be lack of and may be due to poor growth.

18. casual organism: Clavibacter xyli subsp. Xyli Management: Diseased free sets should be sow. Selection of seed from commercial crop. Dipping the sets in hot water at 50 C for 2 hours and pre-soaking.

19. 8- Aspergillus boll rot of cotton Symptoms: The fungal invade the cotton fiber as the result of colonization. It weaken the fiber and cause the discoloration called as yellow strain. Fungus penetrate in the seed coat and colonize the meal portion of the seed. The production of aflatoxins starts in the meal portion of the seed and not in the lint and fiber. Aspergillus f ulvous Disease cycle: Fungus colonize the dead organic matter and produce large number of spores and entry point for fungus into the ball is exit hole of larva of pink boll worm . casual organism :

20. Management: Cultural practices i : e discourage the excessive vegetative growth and moderate use of water and nitrogen. 9- Smut of pearl millet Symptoms: Infection is visible of scattered grains. The infected grains may be single or in the form of clusters and it usually confined in one side of the ear. Smut sori are pear or oval shaped. The top of the sorus is bluntly rounded to conical in shape. The smut grains always double then normal in size. In the beginning the color of the grains is dark green to chocolate brown and later on become dark black on maturity. The color is due to membrane covering the sorus, the enclosed spore mass being always black.

21. Disease cycle: The pathogen is soil borne. The primary inoculum consist of spores balls that have fallen on the ground. They germinate at the time of ear formation in next crop season. On germination they give rise to sporidia which are carried by wind. Secondary infection of late sown crops also occurred by the spores formed in the same season. Management: As the pathogen survive in the soil and the inoculum from soil is air-borne, control of the disease is difficult. So removal of smutted ears, clean seed, hot weather deep ploughing, field sanitation, crop rotation and use of resistant varieties casual organism: Moesziomyces bullatus Management:

22. Management: As the pathogen survive in the soil and the inoculums from soil is air-borne, control of the disease is difficult. So removal of smutted ears, clean seed, hot weather deep ploughing, field sanitation, crop rotation and use of resistant varieties. 10- Stinking Smut or Common Smut or Hill Bunt of Wheat Symptoms: Infected plants remain stunted about the half of the height of normal plant. It’s a systematic disease it starts from the seedlings. The symptoms appear at the time of heading. The smutted ears are darker green than the normal and remain green longer. At the milk stage of grain if punch the grain with thumb a soft black pasty mass id yield. At the time of maturity this black mass change into oily powdery like mass. The presence of stinking can be detected by the found of the presence of a volatile compound tri methyl amine

23. Disease cycle: Inoculum is seed and soil borne. Spores are easily disseminated during threshing and cause infection after 10 years. After passage into the intersnnnjtomal track of the cattle and sheep. Moisture and temperature, host variety, spore load, depth of sowing all these factors affect the infection. The spores usually germinate at 0-4 C. Management: Crop rotation Treatment of seed with 20% copper sulphate formalin 0.5kg in 200liters of water.

24. 1 1- BACTERIAL LEAF BLIGHT OF RICE Symptoms: Symptoms of BLB is vary with stage of infection and prevailing weather conditions. There are two types of phases which involve in the BLB of rice. Leaf blight phase is most commonly seen.it is characterized by Linear yellow to straw color stripes with wavy margins generally on both edges of the leaves rarely on one edge. These stripes usually starts from tip and moves downward .the leaf tip become dry and twisted.in some cases the linear stripes may develop on the lamina on the midrib with or with marginal stripes. In dry weather drops of bacterial ooze which dry into yellowish beads can be seen on the leaf surface. These drops are washed by the rains. The glumes of seed also get infected but symptoms are not well defined. The blight phase usually appear after 4-6 weeks of transplanting

25. casual organism: Xanthomonas oryzae PV. Oryzae Disease cycle: : There can be several modes of perpetuation of the bacterium from one season to other season. It survives during off season in the seeds, weeds host and infected rice straw and stubble. The bacteria survive in the soil only for short period of time. In pond water it has been found to remain viable for 15-18 days. Diseased wild rice growing ponds may provide primary inoculum. The pathogen and its phage (virus) survive longer at 15-20 C than at 30-45 C. The BLB bacteria may present in 54% seeds and may survive there for 120-180 days . Management: Healthy certified seed should be used Proper Field sanitation Deep ploughing and burning of plant debris

26. 12- Bacterial ear rot, Tundo, ear cockle of wheat Symptoms: The first symptom appear as a wrinkling of lower leaf and twisting of central leaf. Bright yellow sticky slimy exuded enveloping the entire ear. During summer the color of exudate become dry and dark yellow in color and this cause the distortion of plant pars. The galls are Produce in the seed that’s why the name as cockle of wheat. The symptoms appears only at the time of maturity. casual organism: Rathayibacter tritici previously known as Clavibacter tritici

27. Disease cycle: Both are necessary for infection. The bacteria survives in infected seed galls. Next year when these galls are sow transmit the disease. The nematode survive in the soil and mechanically enter into the plant and when plant become mature it cause infection so it cause the rooting of ears. Up to 50% symptoms shows presence of bacteria Management: Sowing of galls free seed. Galls can be remove by dipping the seed into brine solution @ 25Kg of salt into 125 liters of water. Collect the galls from the solution and then sow. hot water treatment resoaking at room temperature for 24 hours next day dip in the water temperature of 54-56 C for 10-12 minutes. Soil treatment with carbofuran to control the nematode and also prevent the infection from bacteria. Proper field sanitation

28. 13-Ascochyta blight of chick pea Symptoms: Symptoms almost appear on all Ariel parts. Circular spots on the leaves and pods of 3-4 cm long. Elongated spots on petiole and stem and these spots surrounded by the brownish red margins. In severe attack of the disease the spots may coalesce and cause entire browning of affected leave. Later on these leaves become scotched these Circular lesion occupied by black dots. These black dots are the fruiting body of fungi pycindia. These pycindia are appear in a circular fashion and these pycindia are arranged in concentric circles. The lesions will also appear on stem and gram. . In dry weather the disease spread restricted light shower the disease spread rapidly. The perfect stage of pathogen have been correlated with part of world. Causal organism : Ascochyta rabiei

29. Management: Removal and destruction of infected plant Intercropping of chickpea with cereals Control with agralol, copper sulphate, thiaram, roomy is effected for the control the disease. Use of resistance verities 14- Cotton leaf curl virus Causal organism: Disease causing virus belongs to Gemini group. Symptoms: Thickening of small veins. Thickening of large veins. Enation (leaf like structure) on the underside of the leaves

30. Transmission: White fly is the vector

31. 15-Red stripe and top rot of sugar cane Symptoms: The disease first appear as a water soaked elongated streaks which soon become cholorotic and carry long, uniformly dark red stripes than these stripes coalesce to form large bands. The lower half of the leaf is more affected than the tip. The stripes occur mostly on the young and middle aged leaves rather than oldest. Whitish flakes of dried bacterial ooze may be seen on the lower surface of the leaves. The casual organism: Pseudomonas rubrilineans and another name is Acidovorax avenge subsp. Avenae Disease cycle: The bacterium is not well survive in soil and plant debris. It can infect rice, sorghum, pearl millet etc.

32. These host may serve as agents for carry over the bacterium from season to season. Infection starts through wounds and stomata. The bacterium is confined to young tissues of the host. It rapidly multiplies in the parenchymatous tissues and moves to vascular bundles. Management: Once the disease sets in it’s very difficult to manage. Use of resistant cultivars is the best method to the disease in areas where its occurrence is common. 16-Bacterial leaf strikes of rice Symptoms: It’s a foliar disease. The first sign of the disease is the appearance of fine, water soaked to translucent inter-venial streaks which may be as long as 1 to 10 cm. these strikes are restricted by the veins and soon turn yellow and orange brown. Minute yellow beads of bacterial exudates are abundant on the streaks. Eventually the leaves may be completely blighted. In many susceptible verities streaks are surrounded by yellow halo.

33. The casual organism: Xanthomonas oryzae PV. Oryzicola Disease cycle: The pathogen can in infected seed from one season to other season but not in the crop debris in soil or through weeds. The bacteria hibernate under the glumes in mature seed. 2-3 continuous days with high humidity 83-93% or dew during morning hours are necessary for infection. Favorable temperature is 26-31 C. 17-Wilt of sugarcane Symptoms: The earliest symptoms of the disease is stunting. This is noticed when the plants are half grown. The most striking symptoms is the striking symptoms is the yellowing or withering of the top when the crop is getting ready for harvest , followed by rapid drying of canes. The canes becomes light and hallow. When the canes are split open in the early stage of disease development, the tissues particularly of the lowest internode, have a brick red color with individual vascular strands a dark red.

34. Cereal rust a) Black or stem rust of wheat. b)Yellow or stripe rust of wheat. c)Brown or leaf rust of wheat 18-Black or stem rust of wheat Symptoms. The rusty pustules on the upper surface of leaf, stalk and leaf sheath. These brown pustules burst release the brown powdery masses oral surface telia later on developed in same sorus. The rust fungus effects the physiology of wheat plant. Transpiration increase but translocation of nutrient especially carbohydrates related respiration increase at faster rate. So, this increase usually reflected in the form of symptoms . Causal organism: Puccinia graminis tritici .

35. 19-Stripe rust of wheat or yellow rust Symptoms: This disease appear earlier than black stem rust of wheat before the grains formation. In mild attack uredia appear on leave but in severe attack the pustules also developed on leaves sheath, stalk and glumes. The green color of leaf blade faded in the form of streaks which are usually consist of urediospores of the fungi. So each row consist of series of oval lemon yellow pustule. Pustules arranged end to end like the stitching machine. In severe attack the serial arrangement lost and large patches covered with crowded pustules developed. Causal organism: Puccinia striiformis

36. 20-Leaf or brown rust of wheat Causal organism: Puccinia recondita Symptoms: The uredia develop on leave sheath and stalk. These uredia burst on the upper surface of the leaves as bright orange color points. It appear earlier than stripe rust. They are gathered in small clusters, regular scattered on leave surface. They are bigger in size than the uredia of yellow rust only difference between yellow and leave rust is the leaf rust uredia burst earlier exposing the powdery masses. The sometime teliospore may not develop but if they develop, they are similar to yellow rust. Like small, oval, dull black and covered by the epidermis. Excessive transpiration rate the plant take much more time to produce mature ears. Heavy rusting of foliage result in poorly develop root system Poor quality and quantity of grain and reduce the yield of wheat straw.

37. Dispersal of Urediospore . The dissemination of Urediospore in little initial inoculum increase the varies infection center being continuous by disseminated by wind so, it increase the infection center subsequently because of long distance dispersal of Urediospore, it’s difficult to know whether the primarily inoculum has been brought from nearby place or by hill area. The dispersal distance of uredia spore 38km/h when wind will be about 1760km/h. Epidemiology: Humidity and temperature plays an important role. Germination of Urediospore effected by temperature the optimum temperature is 24 C and very low temperature is not favorable for Urediospore germination. If wetness is prevail for long time than usually 6 hours at 60-65% humidity is required for pustules production, so for the germination of Urediospore in free water or dew deposit on leaf surface for two hours is essential for all three types of rust

38. Management: . Sowing of two different crops at sometimes there is only hypothesis may minimize the primary inoculum. Nitrogen increase the incidence of rust disease whereas potash decrease, so balance application. Use of resistant varieties. . Use of systematic fungicide. . Soil and seed treatment with fungicide.