What herbicides are used against resistant barnyardgrass, arrowhead, three-stem sedge, water onion, rice barnyardgrass and other troublesome weeds?

Every year in mid-June the peak season for herbicide use in rice fields arrives, and many rice farmers ask: resistant barnyardgrass, arrowhead, three-stem sedge, water onion, rice barnyardgrass and other troublesome weeds should be controlled with what herbicides?

1. Control of troublesome weeds such as water plantain, arrowhead, three-stem sedge and water onion

Use 180 ml of 48% bentazon or bentazon, plus 10 g of 56% imported MCPA-dimethylamine salt or MCPA, mix with 30 jin of water, drain the field and then spray the weed stems and leaves; this can cover 600-700 sq m. It can control many troublesome weeds such as wild arrowhead, water cabbage, orchid grass, three-stem sedge, water onion and small cattail, and is safe for rice. Using a certain amount of MCPA every year can make the rhizomes or corms of these troublesome weeds gradually shrink or rot. The weed seeds also cannot mature. Together with autumn plowing, the rhizomes and corms undergo freezing and drying through the winter, which can reduce the regeneration base of rhizomes and corms the following year. When harrowing in spring, the rhizomes and corms that float up should be removed. In this way, using MCPA plus bentazon continuously for three years, spraying the stems and leaves of troublesome weeds at the late tillering stage, can completely control perennial rhizomatous and cormous troublesome weeds such as water plantain, arrowhead, three-stem sedge and water onion.

2. Control of older barnyardgrass

If there is older barnyardgrass, per mu (667 sq m) use 80 ml of 25 g/L penoxsulam (Ricejie), plus 50 g of 40-50% quinclorac, mix with 30 jin of water, and spray the stems and leaves. Use a sprayer with good atomization.

  Note  

If the young panicle differentiation stage has been reached, then chemical herbicides such as MCPA, penoxsulam and quinclorac cannot be used, otherwise phytotoxicity will occur and cause yield reduction! It is best to spray in the morning and evening, and the spraying temperature should preferably not exceed 30°C.

The phytotoxicity of herbicides and their control effect on weeds are affected by many factors. The above formula is for reference only! Or test first, then use.

Rice field weeding steps

First drain the water (or let it dry naturally) and then re-flood:

First, let us explain why applying herbicide requires draining the water first, and then re-flooding after 24 to 48 hours. This is very troublesome; can we not drain the water or not re-flood? Especially large growers often, because of the large planting area, cannot pump water in time, cannot arrange the time, do not drain thoroughly, do not re-flood in time, and do not maintain water properly, causing herbicide phytotoxicity or poor chemical weeding results that lead to weed infestation, directly causing rice yield reduction or total crop loss.

①. When using herbicide, drain the water first, re-flood after 24 hours, and maintain the water for 5-7 days. This can not only effectively kill weeds and ensure rice safety, but is also the key to effectively controlling secondary weed damage.

②. Why should water be drained before using herbicide?

In rice fields, weed control can make use of differences between rice and weeds in morphology, physiology, growth and development, as well as certain characteristics of herbicides, to avoid phytotoxicity to rice. There are usually 5 approaches. Among them, chemical weeding usually adopts 4 approaches: time difference selection, position difference selection, morphological selection and physiological selection; physical weeding adopts 1 approach: spatial selection. In transplanted and seedling-throwing fields, the means we can choose are diverse, and we can choose position difference, time difference, morphological difference, physiological difference and spatial difference to control weeds. In direct-seeded fields, however, weeds usually germinate before the seeds, grow at the same time as rice, or even grow before rice. In the early stage of direct-seeded fields, the semi-arid and semi-humid small environment is very conducive to weed growth. Position difference, time difference and spatial difference cannot be used; only morphological difference and spatial difference can be chosen for weed control. (Therefore, weed control in direct-seeded fields is very difficult.)

Draining the water before using herbicide in rice fields is mainly to make all weeds emerge above the water surface and fully contact the herbicide solution, thereby achieving a better weeding effect. If the water is not drained before using herbicide, or the field is not level and drainage is incomplete, young weeds will not contact the herbicide solution, causing weeding failure and resulting in secondary weed damage.

③. Why should water be re-flooded 24 hours after using herbicide?

Rice, barnyardgrass and Leptochloa chinensis are all grass family plants and are closely related. During chemical control, they actually all receive the herbicide. The reason weeds die while rice does not is that we make use of the different physiological characteristics of rice and weeds; rice can decompose such herbicides itself (such as cyhalofop-butyl, penoxsulam, bispyribac-sodium, etc.). Timely re-flooding is required because rice is more vigorous and better at detoxifying when there is water. Therefore, timely re-flooding is required during use; on the one hand, this is one of the most important reasons for preventing phytotoxicity to rice.

On the other hand, requiring re-flooding after 24 hours is to ensure herbicide efficacy. Sunning the field is one of the important means of promoting rice root development (roots grow in dry conditions, roots grow in aerobic conditions); of course, this means also favors weed root development. If water is not re-flooded in time after using herbicide and the field lacks water, weed roots will develop rapidly, which may allow weeds to survive the herbicide and directly lead to weeding failure.

④ Why should water be maintained for 5-7 days when using herbicide?

The role of maintaining water is very simple: to achieve the purpose of controlling weeds with water. Using the water layer (usually 3-5 cm, not too deep or too shallow) creates a sealing effect on secondary weed germination. Reasonable water maintenance can promote strong rice seedlings and early development, achieve water-based weed control, promote seedlings and suppress weeds, and improve herbicide effectiveness. After maintaining water for 5-7 days, (be sure to combine this with topdressing nitrogen fertilizer, because where rice barnyardgrass occurs, rice has had its field space and nutrients occupied, and its growth is poor. Therefore, fertilizer should be applied after weed killing. In this way, rice growth can be uniform. Achieve a high-yield framework.