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 PPA 601
Plant Diseases and Their Management Lecturer: Esava Tabua WK 4 – Economic Importance, Symptoms, Causal Agents, Disease Cycles and Management of Groundnut, Sesamum and Sunflower Peanut (groundnut) Description • Peanut, Arachis hypogaea, is an herbaceous annual plant. • Family ‐ Fabaceae and its grown for its oil and edible nuts. • Peanut plants are small, usually erect, thin stemmed plants with feather‐like leaves. • The leaves are arranged in alternate pairs and have leaf‐like attachments near the stalk. • The peanut plant produces yellow, orange, cream or white flowers which produce 'pegs', characteristic floral structures which sink into the ground to grow the pod. Cont’d
• The pods can reach up to 10 cm (4 in) in length and can contain between 1 and 5 seeds. • The peanut plant can reach 0.6 m (2 f t) in height depending on the variety and as an annual plant, survives only one growing season. • Peanut may also be referred to as groundnut, monkey nut or earth nut and originates from South America. Uses • Most commercially grown peanuts are used for the extraction of their oil which is used in cooking. • The by product of oil extraction is a pressed cake which is used as an animal feed and also in the production of peanut flour. • Raw kernels are also commonly roasted and eaten as a snack food. DISEASES OF GROUND NUT (Arachis hypogea) • Tikka disease of ground nut: Cercospora
arachidicola (Mycosphaerella arachidis)
• Rust of ground nut: Puccinia arachidis
Tikka disease
DISEASE: Tikka disease PATHOGEN: ercospora • Early leaf spot: C
arachidicola ycosphaerella • Sexual Stage: M
arachidis ercosporidium • Late leaf spot: C
personatum • Sexual stage: Mycosphaerella
berkeleyii HOSTS: Ground nut Symptoms and Signs • The Tikka Disease occurs as two distinct types of leaf spots, caused by two species of Cercosporidium. • Early leaf spot ‐ Cercospora arachidicola • Early Infection leads to circular to irregular reddish brown or dark brown spots with some yellow halo on upper surface of leaves. • Symptoms may also appear on rachis, petioles, stipules and stalks as elongated, elliptical spots with definite border. Symptoms and Signs
• Late leaf spot (Cercosporidium
personatum): Usually late infection leads to circular brown to black spots on lower surface of leaves. • Severe disease attack leads to shedding of leaflets resulting in premature ageing of the crop.
The disease symptom difference ‐ Early leaf spot (ELS) ‐ Cercospora arachidicola to L ate leaf spot (LLS) ‐ Cercosporidium personatum )
Early leaf spot (ELS) ‐ Cercospora arachidicola
Late leaf spot (LLS) ‐ Cercosporidium personatum) Best Suited environmental factors •Wet weather‐High relative humidity (above 8 5 per cent) •Heavy rainfall •Leaf wetness •Moderate temperature of 22 ‐ 25 degrees Celsius. Disease Cycle • The mycelium and conidia of Cercospora in crop residues in the soil and volunteer groundnut plants serve as primary source of inoculum. • The conidia are septate and long. • Every conidiophore generates only a conidium at its tip. • The disease spreads by means of conidia that are dispersed by wind. Management strategy • Grow resistant varieties like Vemana (early and late leaf spots), Naveen, Tirupathi‐3 (early leaf spot only). • General Sanitation: ‐Remove and destroy the infected plant debris. ‐Eradicate the volunteer groundnut plants. • Crop rotation with millets • Seed Treatment with Captan or Thiram at 4g/kg or [email protected]% • Spray [email protected]%or [email protected]% or [email protected]%and if necessary, repeat after 15 days. Control • Plant disease debris should be burnt. • Seed dressing with a suitable fungicide like Benlate and Vitavax (2 gms/kg of seed). • Foliage spray with Bordeaux Mixture (4:4:50), Dithane M‐
45 (0.2%), Benlate and Bavistin (0.1%) gives good results. • Early maturing and spreading type varieties are less liable to attack of the disease. Rust of ground nut
• DISEASE: Rust
• PATHOGEN: Puccinia
arachidis
• HOSTS: Ground nut
Symptoms and Signs •
The disease attacks all aerial parts of the plant. •
Orange colored pustules (uredinia) on the lower surface of leaves. •
Corresponding to the sori, small, necrotic, brown spots appear on the upper surface of leaves. •
Rupture epidermis to release mass of reddish brown uredinio spores. •
Pustules appear first on the lower surface of leaves and then on the upper surface . •
Severely infected leaves turn necrotic and desiccate. •
Late in the season, dark pustules full of teliospores appear . Best Suited environmental factors • Wet weather‐High relative humidity (above 8 5 per cent) • Heavy rainfall • Leaf wetness • Moderate temperature of 22‐250 C. Disease Cycle ‐ Puccinia arachidis • The pathogen survives as uredospores on volunteer groundnut plants. • The fungus also survives in infected plant debris in soil. • The uredospores also spread as contaminants of seeds and pods. • The spread is mainly through wind‐borne inoculum of uredospores. Rain splash and implements also help in dissemination. • The fungus also survives on the collateral hosts like Arachis marginata and A. prostrata. Management strategy
• Avoid mono‐culturing of groundnut. • Remove volunteer groundnut plants and host plants. • Spray Chlorothalonilor [email protected]% ‐ a fungicide. • Arachis glabarata can be used in breeding programme. Cylindrocladium black rot ‐ Cylindrocladium crotalariae Symptoms •
Leaves on main stem turning chlorotic and wilting; entire plant wilts very rapidly when there is a period of water stress following high moisture; clusters of red‐brown fungal bodies occur on stems, pegs and pods; roots destroyed; roots blackened and shriveled. Cause •
Fungus Comments •
Crops planted early are more susceptible to the disease as they are often exposed to cooler temperatures and higher soil moisture; disease can be spread over long distances by wind. Cylindrocladium black rot ‐ Cylindrocladium crotalariae
DISEASES OF SUNFLOWER ‐ (Helianthus annuus L) • Downy mildew of Sunflower ‐ Plasmopara halstedii
• Rust of Sunflower ‐ Puccinia helianthi
Downy mildew of Sunflower
• DISEASE: Downy mildew
• PATHOGEN: Plasmopara halstedii
• HOSTS: Sunflower
Symptoms and Signs •
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Two different types of symptoms: systemic and localized. •
Localized secondary infection takes place through windblown zoospores producing small‐angular chlorotic lesions on the upper leaf surface. •
White cottony masses (fungal mycelium and spores) appear on the underside of infected leaves and are a good diagnostic sign of the disease. •
Flower heads of affected plants remain sterile. Systemic infection is characterized by a thickening and yellowing of midribs of leaves at seedlings stage and affected plants remain severely stunted which ultimately die. Best Suited environmental factors
• Cool –humid weather • Intermittent rains.
Disease Cycle • The pathogen perpetuates in the form of oospores in the soil. • Oospores are round‐to‐oblong and thick walled. They are highly resistant to adverse environmental conditions, and are capable of remaining dormant in soils for up to 10 years. • When soils are saturated and cool (54‐57°F), oospores can germinate and form zoosporangia that release motile zoospores that swim through soil water to infect seedling roots to cause systemic infections. • Those surviving plants will then exhibit signs and symptoms producing inoculum for further spread to cause secondary infections. Management strategy • Hybrids like LSH‐1, LSH‐3, KBSH‐1, Jwalamukhi have a high degree of resistance. • Follow spacing of 60cm x 30cm or 45cm x 30cm. • Rogue out infected plants and destroy. • Cropping sequence of sunflower followed by ground reduces the disease. • Seed treatment with metalaxyl @ 0.6%. • Spray Ridomil MZ( metalaxyl +mancozeb) @ 0.2% at 15 days intervals. Rust of Sunflower
• DISEASE: Rust • PATHOGEN: Puccinia helianthi
• HOSTS: Sunflower
Symptoms and Signs
• Small, reddish brown pustules (u
redina)
covered with rusty dust on the lower surface of bottom leaves. • Infection later spreads to other leaves and even to the green parts of the head. • In severe infection, when numerous pustules appear on leaves, they become yellow and dry. • The black colored T elia are also seen among u
redina on the lower surface. Best Suited environmental factors Warm –humid weather conditions, Intermittent rains and Leaf wetness Optimum temperature for urediniospores germination and new urediopustules formation is 18‐20 degrees Celsius. • Weather parameters like temperatures of 25. 5 degrees to 30.50 degrees Celsius with RH of 86‐92% ‐ favors rust disease severity. •
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Early Season on Seedlings and Volunteer Plants
Disease Cycle • Puccinia helianthi is autoecious rust. In its life cycle the fungus sporulates all stages of development on sunflower. • The pycnial and aecial stages occur on volunteer crops grown during off‐season. • Primary infection occurs by aeciospores released from volunteer plants of sunflower. • The disease spreads by wind (windborne disease – urediniospores. Management strategy • Grow tolerant variety like BSH‐1. • Remove and burn the infected plant debris in the field. • Remove the volunteer sunflower plants. • Crop rotation for 3 years. • Spray Mancozeb@ 0.2% or Tilt (Propioconazole) @ 0.1% 2‐3 times at 10 or 15 days interval. • The first spray should be given as soon as the dis ease is noticed. Crop: Sesamum/ Sesame • Scientific name: Sesamum indicum
• Family: Pedaliaceae
Bacterial blight: Xanthomonas
campestris pv. sesami Symptom • Plants of all stage are affected. • Water soaked, small and irregular spots are formed on the leaves which later increases and turn brown, under favorable conditions. • Leaves become dry and brittle, severely infected leaves defoliate. Management Crop rotation. Use resistant variety ‐ T‐58 variety Early planting i.e. immediately after onset of monsoon. Destruction of crop residues. Steep the seed in Agrimycin‐100 (250 ppm) or Streptocycline suspension (0.05%) for 30 minutes. • Foliar spray of Streptocycline (500 ppm) as soon as symptoms are noticed. • Continue two more sprays at 15 days interval if necessary. •
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Cercospora leaf spot / White spot: Cercospora
sesami, C. sesamicola Symptoms • Disease appears as small, angular brown leaf spots of 3 mm diameter with gray center and dark margin delimited by veins. • In severity of the disease defoliation occurs. Under favorable conditions, the disease spreads to leaf petiole, stem and capsules producing linear dark colored deep seated lesions. Management • Spray Mancozeb 1000g/ha. Damping off / Root Rot:
Macrophomina phaseolina Symptom • The fungus attacks young seedling, their stem become water soaked soft and incapable of supporting the seedling which falls over and dies. • On older seedlings elongated brownish black lesions appear which increase in length and width girdling the stem and plant dies. Management • Soil application of P. fluorescens or T. viride – 2.5 Kg / ha + 50 Kg of well decomposed Farm Yard Manure (FYM) or sand at 30 days after sowing. • Spot drench Carbendazim – 1 gm/ liter Powdery mildew: Oidium sp.,
Sphaerotheca fuliginia, Leveillula sp. Symptom • Small cottony spots appear on the infected leaves which gradually spread on the lamina. • Defoliation of severely infected plant occurs before maturity. Management • Apply any one of the following Sulphur dust 25 kg/ha or Wettable Sulphur 25 kg/ha Sesamum phyllody: Phytoplasma Symptom •
All floral parts are transformed into green leafy structures followed by abundant vein clearing in different flower parts. •
In severe infection, the entire inflorescences is replaced by short twisted leaves closely arranged on a stem with short internodes, abundant abnormal branches bend down. •
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Finally, plants look like witches broom. •
If capsules are formed on lower portion of plant they do not yield quality seeds. Transmission and favourable conditions The disease is transmitted by the vector Orosius albicintus. The phytoplasma survives in leaf hopper throughout its life. Management Remove and destroy infected plants. •
To control vector, spray Monocrotophos 36 or Dimethoate 30 EC 500 ml/ha combined with intercropping of Sesamum + Redgram (6 : 1) Phyllody of Sesame ‐ Sesamum indicum
• DISEASE: Phyllody
• PATHOGEN: Phytoplasma
• HOSTS: Sesamum
Indicum
Symptoms and Signs
• Sesame phyllody is destructive disease associated with Phytoplasma. • The disease transforms the floral parts into green‐ leaf like structures with no capsule / seed formation. • The affected plant gives a bushy appearance with abnormal branching and remains stunted with reduced internodes. • All floral parts are transformed into green leafy structures followed by
abundant vein clearing in different flower parts . • In severe infection, the entire inflorescences is replaced by short twisted leaves closely arranged on a
stem with short internodes, abundant abnormal branches bend down .
Cont’d
• An affected plant bears cluster of leaves and a malformed flower at the tip. • Disease causes considerable loss to sesame oil seed production. • The major symptoms of the disease are floral virescence, phyllody and proliferation. • Finally, plants look like witches broom. are formed on lower • If capsules
they do not yield portion of plant
quality seeds . Transmission is transmitted by the • The disease
albicintus. The vector, Orosius
survives in the leaf phytoplasma
hopper throughout its
life. Best Suited environmental factors
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Dry weather, Moderate temperature (250 C), Low humidity (65%) and Minimum rainfall (0.6mm)
Disease cycle • Phytoplasmas, formerly called mycoplasma‐like organisms (MLOs), are a large group of obligate, intracellular, cell wall less parasites. • The pathogen has a wide host range and survives on hosts like Brassica sp. and some weed hosts. • The disease is transmitted by the vector, Orosius albicinctus (plant/ leaf hooper) in a persistent manner. Management strategy • Grow resistant varieties. • General sanitation ‐Rogue out the infected plants periodically. ‐Remove all the reservoir and weed hosts. Delay sowing to reduce the vector population. Crop rotation‐Avoid growing sesamum near cotton, groundnut and grain legumes. Spray 2‐3 times with a broad spectrum insecticide at flowering stage. Reduces the vector population. •
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Root rot: Fusarium oxysporum f.sp. sesami Symptom • The plant gets infected at any stage of crop development. Symptoms are first visible in the lower leaves and then it progresses upwards. Yellowing, drooping and desiccation of leaves occur. In severe case, entire plant gets defoliated, bends down and ultimately dries up. Vascular bundles turn brown starting from root and gets extended up to tip. •
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Management
in
summer. • Deep ploughing
rotation
• Follow crop
with farm yard • Soil amendment
@ 12. 5 tonnes/ ha is helpful manure
the incidence of the in reducing
disease diseased plant debris by • Destroy the
burning of
burying in the soil .
with T.
• Seed treatment
viride @ 4 g /kg
or P. fluorescens @ 10 g/ kg of seed
or Carbendazim or Thiram 2 g/kg of
seed .
with Carbendazim • Spot drenching
1 g/liter. of P. fluorescens / T.
• Soil application
viride 2. 5 kg/ha
with 50 kg Farm Yard Manure ( FYM ) . Trichoderma viride & Pseudomonas fluorescens •
Trichoderma viride is a fungus and a biofungicide. It is used for seed and soil treatment for suppression of various diseases caused by fungal pathogens. It is also a pathogen in its own right, causing green mould rot of onion. •
Pseudomonas fluorescens is an obligate aerobe, gram negative bacillus. These bacteria are able to inhabit many environments, including: plants, soil, and water surfaces. Its name comes from its production of the soluble fluorescent pigment pyoverdin. •
P. fluorescens is well known for some of its more heroic properties. Firstly it is invaluable to agricultural technologies. These bacteria will reside around the roots of plants/crops. •
P. fluorescens get certain nutrients and environmental protection from the plants they reside near and in return, aid the plant in several ways. They destroy certain toxins and pollutants including styrene, polycyclic aromatic hydrocarbons, and TNT. •
P. fluorescens also protect the plants from infection by pathogens by producing secondary metabolites like antibiotics and hydrogen cyanide which kill other bacteria and fungi. They also keep other pathogens at bay by competitive exclusion due to their rapid colonization. •
It has been theorized that P. fluorescens could be a good alternative to synthetic pesticides because of its toxicity to larvae and the pupae of vector mosquitoes, two main concerns in the agricultural business. References • CABI Crop Protection Compendium. (2010). Arachis hypogaea (groundnut) datasheet. Available at: http://www.cabi.org/cpc/datasheet/6932. [Accessed 06 March 15]. Paid subscription required. • Duke, J. A. (1983). Arachis hypogaea L. Handbook of Energy Crops. unpublished. Available at: http://www.hort.purdue.edu/newcrop/du.... [Accessed 06 March 15]. Free to access. • Kokalis‐Burelle, N., Porter, D.M, Rodríguez‐Kábana, R., Smith, D. H. & Subrahmanyam, P. (Eds.) (1997). Compendium of peanut diseases. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press. • Wright, S. (2012). Peanuts. University of Kentucky College of Agriculture Cooperative Extension Service. Available at: http://www.uky.edu/Ag/NewCrops/intros.... [Accessed 06 March 15]. Free to access. Cont’d •
https://www.plantvillage.org/en/topics/peanutro undnut/infos/diseases_and_pests_description_us es_propagation http://agridr.in/tnauEAgri/eagri50/PATH272/lectu re09/001.html http://www.sunflowernsa.com/growers/diseases /rust‐damage‐and‐control/ http://web.mst.edu/~microbio/BIO221_2009/P_f luorescens.html •
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https://en.wikipedia.org/wiki/Trichoderma_viride THANK YOU