BOTANY Higher Secondary Second Year - Textbooks Online

Control
The infection can be largely prevented by removing the infected
branches and spraying the plants with Bordeaux mixture or spraying 3 to
4 times in a season with antibiotic the
Canker
streptocycline at the rate of 1 gm in
45 liters of water.
Tungro disease of rice
Pathogen Disease incited by a virus
Canker
Rice Tungro virus. The virus is
transmitted by a leafhopper.
Symptoms
The symptoms appear first on the
emerging leaf. They are mild
interveinal chlorosis (loss of
Fig. 6.2 Citrus canker chlorophyll), mild mottling and
yellowing. Plant shows stunted growth and symptoms appear on the lower
leaves. They turn yellow orange, bend downwards and possess dark
brown spots.
Transmission of virus
The leafhopper retains infectivity for a short period only and transmits
the virus to another plant immediately after feeding on an infected plant.
Biopesticides
Biological agents that are used for control of insects, weeds and
pathogens produced from living organisms are called biopesticides. Microorganisms
such as viruses, bacteria, fungi, protozoa and mites may be
used as biopesticides.
Biocontrol of insect pests
1. The manufacture of methyl isocynate (MIC) was started in 1980 in
India to make Serin (carbaryl), a powerful pesticide that can kill more
than 100 types of insects attacking 100 different crops.
2. Many of the chemical pesticides, which are used to control several
crop pests also affects the beneficial organisms.
242