Damages Or Losses Caused By Weeds

Damages Or Losses Caused By Weeds or Disadvantages of Weeds

1. Reduction in crop yield: Weeds compete for water, nutrients & light. Being hardy & vigorous in growth habit, they soon outgrow the crops & consume large amounts of water & nutrients, thus causing heavy losses in yield. E.g.: 40% reduction in yield of groundnut & 66% reduction in yield of chilli. The loss of N through weeds is about 150 kg/ha.

2. Increase in the cost of cultivation: One of the objects of tillage is to control weed on which 30% expenditure is incurred and this may increase more in heavy infested areas & also cost on weed control by weeding or chemical control. Hence, reduce margin of net profit.

3. Quality of field produce is reduced: Weed seeds get harvested & threshed along the crop produce which lowers the quality. Such produce fetches fewer prices in the market. E.g.: Leafy vegetables, grain crop.

4. Reduction in quality of livestock produce: Weeds impart an undesirable flavor to the milk (Ghaneri), impair quality of wool of sheep (Gokhuru, Aghada), and cause death of animals due to poisonous nature of seed (Dhatura).

5. Harbour insect-pests & disease pathogens: Weeds either give shelter to various insect pests & disease pathogens or serve as alternate hosts & thus helps in perpetuating the menace from pests & diseases. E.g.: Gall fly of paddy, midge fly of Jowar, leaf minor of soybean & Groundnut, rust of Wheat, tikka of Groundnut, Black rust of wheat ,Downey mildew (Saccharum spontaneum).

6. Check the flow of water in irrigation channels: Weeds block drainage & check the flow of water in irrigation canals & field channels thereby increasing the seepage losses as well as losses through over through over flowing, so reduce the irrigation efficiency.

7. Secretions are harmful: Heavy growth of certain weeds like quack grass (Agropyon repens) or lavala lowers the germination & reduce the growth of many crop plants due to presence of certain phytotoxins secreted by weeds.

8. Harmful to human beings and animals: Weeds cause irritation of skin allergy & poisoning to human beings, also death of castles.

9. Cause quicker wear & tear of farm implements: Being hardy & deep rooted; the tillage implements get worn out early & cannot work efficiently unless they are properly sharpened or mended.

10. Reduce value of the lands: Heavily infested lands with perennial weeds fetch less price as require heavy expenditure to brought under cultivation.

Principles Of Weed Control

For successful control, one has to consider the following points:

1. Habits of weed plants: A xerophytes weed (E.g. Alhagi camelorum) thriving under dry & arid conditions will die if fields are flooded with water. Similarly weeds which thrive under marsh or ill drained condition of soil can be controlled by improving drainage.

2. Life cycle of the weed: Annuals & biennials can be controlled effectively if the land is cultivated before seedling stage of weeds. Perennials require deep ploughing to dig out rhizones, bulbs, etc. vegetative part by which they propagate.

3. Susceptibilities: Some weeds are susceptible to certain chemicals while others are not. E.g.: Dicots are susceptible to 2, 4-D while monocots are not, hence 2,4-D is used to control broad leaved weeds in monocot crops.

4. Dormancy period: While controlling dormancy weeds, period is to be considered as they have long dormancy period.

5. Resistance to adverse conditions without losing viability: Some weed seeds have hard seed coats which enable them to remain for a long time without losing their viability, hence they should be controlled before seed formation.

6. Methods of reproduction: Weeds propagate either by seeds, vegetative parts or by both. Seeded weeds should be removed or smothered before seed formation. Vegetatively propagated weeds should be exposed to sun heat to dry & die like rhizome, bulbs, solons, etc. by deep ploughing. Frequent cultivation leads to destroy green leaves & thereby exhaust the food reserves & starve the plants may have to be restored too. In weeds propagated by both mechanical & chemical methods may have to be followed.

7. Dispersal of seeds: Weeds can be controlled or kept in check if the ways in which different weed seeds disseminate are known and counter measures are undertaken.