Diseases of Vegetable, Ornamental and Spice Crops

QUESTIONS

Q.No. 1. Tick the correct answers
1. Downy mildew of onion is caused by:

a) Fungi b) Bacteria c) Virus d) Nematode

2. Systemic infection of downy mildew occurs when:

a) Infected seed used b) Infected bulb used c) Weed host in the vicinity d) Allium weeds in the vicinity

3. Peronospora destructor perpetuate in the form of:

a) Chlamydospore b) Oospore c) Conidia d) Perithecium

4. Downy mildew development is favoured by:

a) Low temperature and high humidity b) High temperature and High humidity c) Low temperature and low humidity d) 13o C temperature and > 95% RH

5. Downy mildew severity can be checked by sprays of:

a) Metalaxyl + mancozeb b) Wettable sulphur c) Hexaconazole d) difenconazole

6. Sexual stage of Alternaria porri is:

a) Glomerella cingulata b) Diaporthe vexans c) Unknown

d) Helminthosporium sativum

7. Alternaria porri survives as:

a) Mycelium in plant debris b) Spores in plant debris c) Conidia in plant debris d) Ascospores in plant debris

8. The teleomorphic stage of Stemphylium vesicarium is:

a) Albugo candida b) Alternaria solani c) Pleospora allii d) Diaporthe vexans

9. Fusarium basal rot pathogen overwinters in the form of:

a) Sclerotia b) Conidia c) Chlamydospores d) Cleistothecia

10. The pathogen associated with white rot is:

a) Sclerotium rolfsii b) Sclerotium cepivorum c) Sclerotinia sclerotiorum
d) Rhizoctonia solani

11. Soil solarization for the management of white rot is normally done during the months of:

a) Winter b) Rainy c) Spring d) Summer

12. Onion smut fungus perpetuate in the form of:

a) Conidia b) Oospore c) Chlamydospore d) Cleistothecia

13. Onion smudge is caused by:

e) Colletotrichum lindemuthianum b) Colletotrichum capsici c) Colletotrichum circinans d) Colletotrichum gloeosporioides

Answers: 1 a 2 b 3 b 4 d 5 a 6 c 7 a 8 c 9 c 10 b 11 d 12 c 13 c

Q. No. 2. Fill in the blanks

1. ------------------------ and ----------------- coupled with ------------------------- favour Stemphylium blight initiation and development.
2. Downy mildew causes two types of infection i.e. ---------------- and----------------------.
3. Sporangiophores of Peronospora destructor are------------------ at the base and-----------------times dichotomously branched.
4. The main source of downy mildew primary infection is ------------------ in infected onion bulbs.
5. For downy mildew development ---------o C and --------% RH are optimum.
6. Alternaria porri conidia are ------------- and are usually--------------------.
7. Each cell of Alternaria porri conidium is capable of germination by-------------------.
8. Sexual stage of Alternaria porri is--------------------.
9. The optimum temperature for the growth of Alternaria porri is-----------------o C.
10. Spore germination of Alternaria porri increase with the increase in --------------- on leaves.
11. To avoid Alternaria porri seed borne inoculums, treat the seed with-------------------.
12. In garlic crop, Stemphylium blight symptom appear on the ------------- side of the leaf.
13. Conidium of Stemphylium vesicarium have ----------------- transverse septa and -------------- longitudinal septa.
14. Conidia of Stemphylium vesicarium are --------------- at the major transverse septa.
15. Perithecia of Stemphylium vesicarium mature within --------------- months.
16. ------------------ temperature and ------------------- coupled with ---------------- favour the Stemphylium blight.
17. Stemphylium blight is effectively managed by sprays of--------------------- along with ----------------.
18. Ascospores of Pleospora allii are---------------- and the --------------half is narrowly---------------.
19. The main symptoms of basal rot are ---------------- and rapid ----------- back of leaves from the tip.
20. Due to Fusarium basal rot infection, bulbs become-------------- and when cut a ---------------------- is noticed.
21. Species of Fusarium produce --------------, ----------------------- and ---------------------------.
22. Fusarium spp. disseminate widely through infected----------------- and --------------- cloves.
23. Fusarium spp. are-------------------- soil inhabitants.
24. Sclerotium cepivorum is ---------------- borne and remains ---------------------- indefinitely.
25. The symptoms of onion blast appear as -------------------- with------------------------ surrounded by --------------- halo.

Answers

1. 1 Moderate temperature, humidity, precipitation 2. Local, Systemic 3. Swollen, 3 to 4 4. Mycelium 5. 13 , > 95 6. Muriform, Solitary 7. Germtube 8. Unknown 10.Potassium, 11. Captan 12. Inner 13.One to six, one to three 14. Constricted 15. 3 to 6 16. Moderate, Humidity, Precipitation 17. Mancozeb, Sticker 18. Ellipsoidal, upper, tapered 19. Wilting, drying 20. Soft, Watering, Decay 21. Microconidia, Macroconidia, Chlamydospores 22. Onion sets, Garlic 23. Persistent 24. Soil, Viable 25. White specks, Necrotic centre, light green.

Subjective type questions:

1. Describe in detail the symptoms and management practices of following diseases

a) Purple blotch
b) Stemphylium blight
c) Downy mildew

Q. No. 3. Write down the management practices of the following diseases:

a) Onion smut
b) Onion blast
c) White rot