Mustard.disease pest management and their control measure

Mustard

1. Diseases of Mustard

2. Importance of Mustard India occupies the first position both in area and production of rape seed and mustard. 2 nd – edible oilseed (27.8% in Indian oilseed economy) Oil cake Oil content (30-40%) Oil content [White mustard] (25-33%) Condiment Used as vegetable

3. Alternaria blight of mustard Alternaria blight causes 32-57 % of average yield loss Symptoms The fung u s att a cks t h e lower l e aves as sma l l c irc u l a r brown necrotic spots and slowly increase in size. In severe c as e s m any conc e n tr i c s pots c o ale s ce t o co v er l a r g e patches showing blightening and defoliation. Circular to linear dark brown spots also develop on stems and pods which becomes elongated at later stage. Infected pods produce small discolored and shriveled seeds.

4. Alternaria blight of mustard

5. Causal organism Alternaria brassicae (fungus) Pathogen Conidia are the asexual spores formed. They are formed in chains or solitary, typically ovoid to obclavate, often beaked, pale brown to brown, multi-celled and muriform. Disease cycle C o nid i a are spre a d b y w i nd or rain. They fall on leaves and also on pods. The i n fec t e d i n fec t ed seeds pods c o n t ain and conidia remains in stubbles. Infected seeds give rise to seedlings which contains the pathogen.

6. SU R VI V AL AND SP R EAD Disease is externally and internally seed borne Pathogen survives through conidia or mycelium in diseased plant debris or weed Relative humidity more than 70% coupled with warm weather (12-25 ° C) and intermittent rains favor disease development

7. DISEASE MANAGEMENT Healthy seeds to be used for sowing. Affected plant portions should be collected and burnt. De e p p l o u g h ing, ti m ely we e d i ng and m a i n tenance of optimum plant population. Spraying soil isolates of Trichoderma viride at 45 and 75 days after sowing. S p rayi n g M a ncoz e b @ . 2 K g in 100 l of w a ter per hectare as soon symptoms appears.

8. WHITE RUST OF MUSTARD Symptoms All aerials parts of the plant are attacked. White or creamy yellow pustules of various shape and size appears on the surface of the leaves, mainly on the lower surface. I n sev e re i n fec t ion the le a ves be c o m e thi ck , f l esh y , inrolled and their size becomes reduced. I f you n g ste m s and i n fl o r e sc e nce a r e i n fec t ed the fungus becomes systemic inside tissues and produces def o r m it i es like s w el l ing and dist o r t i o n of the fl o ral parts m ainly du e t o hyp e r t rophy a n d hyp e r p l a sia forming a staghead structure.

9. SYMPTOM ON FLORAL PART

10. SYMPTOM ON LEAF

11. CA U SAL ORG A NISM Albugo candida Mycelium of fungus is intercellular forming knob like haustoria in the host cells Hyphae for m s beneath t h e e p i d er m is and i t give s rise t o t h e sporangial beds or sori Sporang i op h ore s arise from the sor i are free fr o m each other laterally and are very thick towards the base Sporangia a r e for m ed i n bas i p etal succes s i o n i n cha i ns a r e hyaline, and spherical and produces zoospores Oogonia and anthredia are formed from intercellular mycelium in intercellular spaces Oospores a r e for m ed f r om th e ir fe r ti l iz a tion i n host s and their germination takes place by formation of zoospores

12. Disease cycle Pathogen perpetuates through the oospores lying in soil or diseased debris. Weed hosts serve as primary source of inoculum. Secondary spread of pathogen is by sporangia and zoospores.

13. EPI D EMIOL O GY The sporangia germinates at an optimum temperature of 10 ° C . RH should be more than 65% with less temperature of 15 ° C. Crops sown late are more disease prone.

14. MANAGEMENT Destruction of weeds in and around the fields should be done. Crop rotation. Rotation with non-cruciferous crops. Seed dressing with Metalaxyl @6g/kg seed followed by a single spray with Metalaxyl + Mancozeb (Ridomil gold)@0.2%.

15. DOWNEY MILDEW OF MUSTARD Symptoms Grayish w h i t e i r r eg u lar necr ot ic p atches dev e l o p o n the l o wer surface of the leaves. The upper surface o f the lea v es y e l l ow spot i s t h e r e corresponding to necrotic spot on lower surface. La t er under favoura b le con d itions brownis h wh i te fung a l m ay also be seen on the spots. The most pronounced symptom is the infection of inflorescence causing hypertrophy of peduncle.( Stag head) The affected inflorescence does not produce any siliqua or seed.

16. DOWNEY MILDEW OF MUSTARD

17. CA U SAL ORG A NISM Peronospora parasitica Peronospora is an obligate parasite , mycelium is intercellular with large finger shaped haustoria. Nu m e r ous branc h ed s poran g iophores e m e r ge th r ough t h e stomata on undersurface of leaves. Sporangiophores are 6-8 times dichotomously branched at the tip, each tip producing one sporangium . Spherical, hyaline oogonium is fertilized by single anthredium and produces pale yellow coloured globose oospores.

18. DISEASE CYCLE Sporang i a lands on suitable host germinates, produces appressoria and enters into the host epidermis. The hyphae grows intercellularly forming haustoria. They produce spora n giophore b earing sp o rang i a (ase x ual cycle)and also anthredium and oogonium which fertilizes to give the oospores (sexual cycle) . Pathogen survives in the form of oospores. They occur on the surface and in the hypodermis of seed coat and these infected seeds produce seedlings with downey mildew symptoms. Wild hosts also serve as a source of primary inoculum. Secondary spread caused by sporangia.

19. EPIDEMIOLOGY Temperature in the range of 10-20 ° C and relative humidity more than 90% favours disease development. Disease management Collect and destroy infected plant debris. Rotation with non-cruciferous crops. Seed d r essi n g wi t h Met a laxyl (Ap r on 35 SD) @ 6 g / kg seed . Si n g l e spray with Met a lax y l + Mancoz e b (Ri d o m il gold)@0.2%.

20. SCLEROTINIA STEM ROT SYMPTOMS Stems develop water soaked spots near to crown region which later may be covered with cottony white mycelium. As disease progresses the affected portions of stem develops a bleached appearance at the internodes and eventually the tissues shreds. Premature ripening and shredding of stem , wilting, and drying In later stage black sclerotial bodies are also seen on infected plants.

21. SCLEROTINIA STEM ROT

22. CA U SAL ORG A NISM Sclerotinia sclerotiorum Asexual spores (conidia) are not formed Sclerotia is the survival structure. Disease cycle Primary infection : scleroticnia survive in soil. Secondary infection : By irrigation water. Favourable conditions High hu m i d ity (90-95 % ) and aver a ge t e m pera t ure (18-25 o C ) along with wind current favours the disease development.

23. MANAGEMENT Use crop rotation; do not plant highly susceptible crops more than once in four years, including dry edible beans, sunflowers, mustard and canola. Use at least a five year rotation for severely infested fields. Avoid planting next to a field that had severe Sclerotinia in the past four or five years. Control broad-leaved weeds. Plant thoroughly cleaned seed. Avoid dense stands of canola.

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