Viral diseases

What is a disease

Disease is an impairment of the normal state of the plant or of any of its components that interupts or modifies the performance of the vital function, being a response to environmental factors, to specific infective agents, to inherent defects of the plant, or to combinations of these factors.

What is a virus

Virus is a strand of DNA or RNA, consisting of a nucleic acid wrapped in a thin coat of protein. It is a very infectious that multiplies itself only within the cells of the living hosts.

Symptoms of viral disease

Leaf curl causes the leaf margin to roll either inward or upward and is rather stiff with yellowish margin. The leaves become thicker than normal, with leathery texture.

Mosaic causes the normal green color of leaves to become mottled with light green, yellow, yellow-orange, or white irregularly shaped patches. If often results in the yellowing of the plants (chlorosis).

Ring spot causes ring of pale or yellow spots on the leaves.

Rosetting causes short and bushy growth. The leaves and the side branches grow in a crowded circles from a common center or crown, that they grow in a rosette (rose-liked form), hence the name.

Stunted growth causes the plant to be dwarfed and of inferior size and quality.

Prevention and control

1. Control insect pests that are normally the carriers of viral disease; like aphids, leafhoppers, and whiteflies
2. Protect your seedlings with row covers to prevent them from early attack of the abovementioned pests
3. Uproot the heavily infected plants
4. Always practice proper field sanitation
5. Control the weeds
6. Always remember not to work on your plants when they are wet

External links

• agLearn.net - A Network for Sustainable Agriculture. The third rule of rice IPM - Agroecosystem management. http://www.aglearn.net/riceIPMModule4.html

References

• Brooklyn Botanic Garden. (2000): Natural disease control: A common-sense approach to plant first aid. Handbook # 164. Brooklyn Botanic Garden, Inc. 1000 Washington Avenue, Brooklyn, NY.
• Ellis, B.; Bradley, F. (1996): The organic gardener's handbook of natural insect and disease control. Rodale Press. Emmaus, Pennsylvania.
• Ploetz, R.; et. al. Editors. (1998): Compendium of tropical fruit diseases. APS Press, The American Phytopathological Society. Saint Paul, Minnesota, USA.