Bordeaux mixture, used in agriculture, is prepared from
- A.copper sulphate and lime
- B.zinc sulphate and urea
- C.sulphur and common salt
- D.ferrous sulphate and gypsum
Correct answer
Explanation
The correct answer is A, copper sulphate and lime. Bordeaux mixture is a suspension made by adding a solution of copper sulphate to one of lime, and it is the oldest fungicide still in regular use; it was devised in the Bordeaux region of France against downy mildew of the grapevine and is sprayed today on fruit trees, potatoes and vegetables against leaf spots and blights. Option B is wrong because zinc sulphate is applied to correct a zinc deficiency, as in khaira of rice, and urea is a nitrogen fertiliser, so neither acts against a fungus. Option C is wrong because sulphur alone is indeed a fungicide against powdery mildew, but common salt is not part of any standard mixture. Option D is wrong because ferrous sulphate corrects iron chlorosis and gypsum is used to reclaim alkaline soils and to supply calcium and sulphur, which are soil amendments rather than disease control.
Read the full article: Plant Diseases and Their Causes: Notes for Exams
Practice Questions
View allLate blight of potato is caused by which organism?
- A.A virus
- B.Phytophthora infestans
- C.Xanthomonas citri
- D.Meloidogyne incognita
Show answer
The epidemic of the 1840s destroyed the potato crop of Ireland and brought on the famine, and the study of that outbreak by Anton de Bary established plant pathology as a science.
Read the full explanation →Rust of wheat is caused by a fungus of which genus?
- A.Puccinia
- B.Ustilago
- C.Fusarium
- D.Claviceps
Show answer
The rusts of wheat, named black, brown and yellow after the colour of the pustules they raise on the stem and leaves, are caused by species of Puccinia, and resistance to them was one of the traits selected in the dwarf wheats of the Green Revolution.
Read the full explanation →Red rot, one of the most serious diseases of sugarcane, is caused by
- A.Colletotrichum falcatum
- B.Ralstonia solanacearum
- C.a phytoplasma
- D.a nematode
Show answer
The correct answer is A, Colletotrichum falcatum, a fungus that rots the internal tissue of the cane, turning it red with white patches and giving it a sour smell, and which spreads mainly through infected setts used for planting.
Read the full explanation →Citrus canker in plants is caused by
- A.a fungus
- B.a bacterium
- C.a virus
- D.a deficiency of boron
Show answer
Citrus canker is caused by a species of Xanthomonas, which enters through wounds, insect punctures and stomata and raises raised corky brown lesions, often with a yellow halo, on leaves, twigs and fruit; it spreads in splashing rain, on tools and on infected nursery plants.
Read the full explanation →Khaira disease of rice is caused by the deficiency of which nutrient?
- A.Zinc
- B.Boron
- C.Molybdenum
- D.Copper
Show answer
In khaira disease the leaves of young rice plants develop rusty brown spots that spread until the crop looks scorched, tillering is poor and growth is stunted; an application of zinc sulphate to the soil or as a foliar spray corrects it, which confirms that the cause is a deficiency…
Read the full explanation →