- Weed is a plant in the wrong place. On the other hand, weeds may be valuable plants in other situations. This fact is fundamental to a consideration of biological control. In fact the method of biological control of weed has been used when other methods found inadequate. To reduce the densities to non-economic levels by either direct or indirect action of natural enemies being used.
Fundamental of Biological Control of Weed
- Concept of Natural Control as Related to Weed:
- The competitive weed should be fast-growing e.g. Stylo.
- Kind of Natural Enemies:
- Species insect feeding made preferred roots, stems, seeds and flowers.
- Nature of Controlling Action:
- Every weed cannot be controlled biological with insect.
- a. Injury:
- Direct feeding on vital parts like flowers, seeds or killing the plants. Indirect feeding injury increase susceptibility to diseases or secondary parasites.
- b. Plant Parts Attacked:
- Vital plant part should be attacked before seed formation.
- Inter Relation of the Insect Agent and Food:
- Struggle for existence, Insect attacked weed become weak and other species may become dominant. Disturbance to plant feeders by natural calamities.
- Risk of Introduction and Host Specificity:
- Great fear of become weed feeder as feeder of economic plants.
- Specificity Tests, Starvation:
- Leaf beetle, allied to host or even more on cabbage but found not multiplied in field.
- Nature of Infection and Prospectus of Success:
- Successful weed killer should have no pest of economic plants, should attack vital plant parts, should have least natural enemies and should have fast multiplication rate.
|Two beetles: Octotoma scabripennis and Uroplata giraldi||Lantana camara|
|Prickly-pear weed – Opuntia|
|Alligator weed –|
|Common carp (Cyprimus carpio)|
|Mammals Manetee or sea-cow||Water hyacinth|
|Snails Marisa sp and other fresh water snails||Submerged weeds like coontail and algae|
|Fungi Rhizoctinia blight.||Hyacinth|
|Tetranychus sp||Prickly pear|
|Plants Cowpea as intercrop in sorghum||Effectively reduces the growth of weeds in sorghum|