BSc Tran Thanh Tin

Weeds are one of the pests that often appear in the field, with high tolerance, strong growth they compete for nutrients and water, affecting the growth and development of rice plants, and at the same time providing shelter. hiding of mice and other harmful pests etc…

Winter-Spring crop often has cold weather, prolonged rain and cold, so improper use of herbicides can affect the growth and development of rice plants. Therefore, the problem of weed control at the right time, in the right way is a very urgent requirement. To do this well, we need to identify the weeds present in the field to choose the appropriate herbicide and time to handle the herbicide.

I. CLASSIFICATION OF WEEDS

1. Classification by morphology

- Monocotyledonous weed: weeds in grass weed and sedge weed groups: Echinochloa sp, Leptochloa chinensis,Fimbristylis miliacea etc..

- Dicotyledonous weed: Broad-leaved grasses such as Monochoria vaginalis, Marsilea minuta ,Ludwigia octovalvis etc...

2. Classification according to botanical characteristics

- Group of grass weeds: There are solid and hollow internodes, round body. The leaf blade is narrow, long, the secondary veins parallel to the main veins running from the leaf tip to the leaf collar. Stems are round and hollow, leaves are alternate, attached to the stem in two rows. Roots are usually cluster roots, growing shallowly.

- Group of sedge weeds narrow leaves but shorter than the grass weed, the stem is usually solid with a triangular angle. Regardless of leaf sheath and leaf blade, leaves are attached to the stem in 3 rows around the stem. The base of the leaves forms a tube around the stem.

- Group of Broadleaved-weeds: broad leaves, horizontal, opposite growth, leaf surface less hairy, leaf veins arranged in different phenotypes (retinal veins for dicotyledonous weed and leaf veins parallel to the monocotyledon)

II. MANAGEMENT AND WEED CONTROL ON SOWING RICE FIELD.

1. Cultivation method

- Plow over the soil before harrowing to sow about 20-25 days to bury the remnants of weeds, ratoon rice and limit harmful organisms. Note that before plowing over the soil, collect crop residues, especially weeds and flowers, and destroy them.

- Make the soil carefully, the field surface is flat, well drained and fertilize according to the process, especially phosphate fertilizer to create conditions for the rice plants to have enough nutrients for the rice plants to absorb and grow after taking root and greening recovery, quick development overwhelms weeds, and at the same time enhance the resistance of rice when facing unfavorable external conditions.

- Use standard varieties for sowing, in order to limit the possibility of mixing weed seeds from the seed source. Before soaking, it is necessary to sift to remove unfilled seeds, half-unfilled seeds and weed seeds.

- After sowing, depending on the weather conditions and the growth stage of the rice, it is necessary to regulate the water level in the field appropriately to limit weed growth and when the weather is favorable (appropriate temperature). herbicides can be used to treat and based on the time and type of weeds in the field to choose suitable herbicides

2. Chemical measures

- There are many herbicides on the market. Each product has different herbicide active ingredients, Depending on the time and condition of the weeds in the field to choose the right product to use. Prioritize choosing products with high weed control efficiency and low toxicity to humans and the environment.

- Group of pre-emergent herbicides: Used before weeds are seen in the field to prevent them from appearing

- Group of post-emergent herbicides: Used when the weed has appeared in the field, the weed has 1-2 leaves.

- To helpcontrol weeds in rice fields well during the cultivation period, we would like to introduce 2 rice herbicidal products of Saigon Plant Protection Joint Stock Company:

+ Bebu 30 WP herbicide:

Bebu 30 WP is an early pre-emergent and early post-emergent herbicide, containing 2 active ingredients Butachlor 28.5% + Bensulfuron Methyl 1.5% (safener of Fenclorim 10%) effective against all three groups of grass weeds, sedge weeds and broadleaved such as: Leptochloa chinensis ,Echinochloa sp  Digitaria sp, Cyperus difformis, Fimbristyslis miliacea, Monochoria vaginalis, Marsilea minuta ,Rotala indica... Safe for rice plants

The product has a selective, contact and internal absorption effect, penetrates into the plant through leaves, roots and shoots, so it has a very effective herbicide effect at the stage when the seeds have not yet grown, newly-sprouted weed seeds and weeds have grown but still young (1 - 2 leaves)

Spray when sowing 1-3 days, dose 60g / 20-liter- tank, spray 02 tanks for 1,000 m2

Pataxim 55 EC herbicide:

+ Pataxim 55EC is a post-emergent herbicide, containing 2 active ingredients Butachlor 275g/l and Propanil 275g/l. The combination of these 2 active ingredients has the effect of enhancing the effectiveness of all 3 groups of weeds and prolonging the use time

+ Spray when sowing from 4 to 12 days, corresponding from the time the weed has just grown to the weed with 3 leaves

+ The amount of product used is from 2 - 2.5 liters/ha, mix 80 - 120 ml of product/ 20 liters of water, spray the field surface from 2 - 2.5 tanks for the field of 1,000m2. Spray early, use low dose, spray late, use high dose according to the instructions on the product label.

- Notes when spraying herbicides:

When spraying the field, it is necessary to drain the water, but keep it moist enough. After spraying 1-3 days, water should be applied to the field, adjusting the field water level in accordance with the growth stage of the rice plant.

Do not spray herbicides when it is about to rain, strong winds or when the outdoor temperature drops below 18⁰C.