Predominant Weeds in Vegetable Crops And Their Management

The vegetable fields are usually infested by a wide spectrum of broad-leaved and grassy weeds, which reduce the yield by competing for moisture, nutrients and light during the growing season. Weeds also harbour insects, pathogens and interfere with harvesting and also lower the quality of crop seeds by mixing with them. Thus, if weed control is not carried out timely, the reduction in yield will be more.

The research conducted at various agro-climatic regions of India evinced that vegetables are more sensitive to early weed competition, which substantially reduce vigour, uniformity and the overall yield thus accentuating the weed control at early crop stages. The critical period of weed competition is usually longer in direct-seeded vegetables than in transplanted crops. Hence, successful weed control is essential for the economic production of vegetable crops. This includes a combination of management practices viz., crop rotation, cover cropping, high planting density, mulching, inter cultivation, flooding, and herbicide use, designed to suppress the weeds. The weed species which are predominant in a particular crop should be known for formulating a suitable weed management strategy.

Tomato

• Tomato requires frequent shallow cultivation, especially during the first four weeks after transplanting. The improper weed management can cause the yield loss of 40 – 60%. Mulching with straw, black polythene and other materials help in moisture conservation and control the weeds effectively through the smothering effect thus favouring better quality and yield.

• Two hand hoeings in the first and third fortnight after transplanting are essential to suppress the growth of weeds

Chemical control:

Fluchloralin  or pendimethalin at 1.25 kg ai/ha as pre plant incorporation

Oxyfloufen 0.25 kg ai/ha

Metribuzin at 0.35 kg ai/ha

Nitralin/ trifluralin at 0.75-1.0 kg ai/ha

Alachlor  at 1.0-1.25 kg ai /ha

Nitrofen  at  1.0 kg ai/ha

Oxadiazon  at 1.0 kg ai/ha

Diphenamid at 4-6 kg ai/ha

Brinjal

• Mulching with sugarcane trash on 18 days after transplanting reduces the infestation of weeds by averting light from reaching the weeds (Sha and Karuppaiah, 2005).

Chemical control:

Fluchloralin  at 1.0 kg ai/ha

Pendmethalin  at 1.0 kg ai/ha

Butachlor at 1.5 kg ai/ha

Oxadiazon  at 0.5 kg ai/ha

Alachlor at  2.5 kg a.i/ha

Paraquat at  0.5 kg a.i/ha  as directed spray in the  inter rows by using protective hood.  

Chilli

• The weeds pose more problems in chilli which is due to up right nature of the crop, wider spacing, slow initial growth and less area occupied by the canopy.

• Growing of onion, greengram and bhendi as intercrops reduce the incidence of weeds

• Hand weeding should be done for 3-4 times after the application of pre emergence herbicides for obtaining optimum

Chemical control:

• Nitralin or Trifluralin at 1.0 kg ai/ha

• Nitrofen at 1.5 kg ai / ha

• Alachlor at 2.5 kg ai/ha

• Pendimethalin at 1 kg ai/ha

• Oxadiazon at 1 kg ai/ha

• Fluchloralin  at 1.25 kg ai/ha.

Bhendi

• This crop should be protected from weeds up to 60 days. The reduction in yield due to weeds varies depending on the density and nature of weed infestation and other management practices. Generally it varies from 60 to 70% if the weeds are not controlled.

Chemical control:

• Fluchloralin at 1.5 kg ai / ha

• Alachlor at 2.5 kg ai / ha 

• Benthiocarb at 2 kg ai / ha

• Oxyflurofen at 0.35 kg ai / ha

• Nitrofen at 2 kg ai / ha

One hand weeding on 25-30 days after sowing can be done after the application of               aforementioned herbicides as pre emergence.

Potato

• The agro techniques adopted for potato provide favourable conditions for early germination and establishment of weeds well before the potato crop emerge. The most critical period for crop-weed competition is from 4-6 weeks after planting (Thakral al. 1985a). If early control measures are not taken, the weeds completely smother the crop in early stages resulting in lower yields. Some weeds like Cyperus rotundus may damage the tubers by growing through them and resulting in deterioration of quality. 

• Growing of vigorous and fast growing potato varieties viz., Kufri Badshah and Kufri Jyoti are helpful in suppressing the weeds as they cover the ground rapidly through its wider canopy.

• Inclusion of smother crops like cowpea and green manure crops in potato based cropping system reduces the infestation of weeds by depriving them of sunlight.

• Mulching can be done by the use of polythene films, dry straw, grasses and other plant parts for controlling weeds.

• Animal-drawn three tine cultivator, popularly known as Triphali, is a very useful implement for weeding and tilling in potato (Shyam and Singh, 1979).

Chemical control:

Pendimethalin  at 1.0 kg ai /ha is applied as pre-planting and incorporated in the soil but it can also be used as pre-emergence.        

2, 4-D.   at 0.5 kg ai/ha

Alachlor  at 1.5 kg ai/ha

Isoproturon at 0.5 kg ai/ha (Randhawa et al., 1985).

Methabenzthiazuron: at 1.0 kg ai/ha

Nitrofen at 1.0-1.5 kg ai/ha.

Oxyfluorfen  at 0.1 – 0.2 kg ai / ha.

Ametryn  at 1.0 kg ai/ha.

Atrazine at 0.5 kg ai/ha

Metribuzin at 0.7 – 1.0 kg ai /ha .

Prometryn at 0.5 – 1.0 kg ai/ha

Simazine at 0.3 – 0.5 kg ai/ha.

Terbutryn at 1.0 kg ai/ha

Post emergence herbicides

Paraquat at 0.4 – 0.6 kg ai /ha  as early post-emergence (5 – 10 per cent emergence of potato) or Propanil at 1.0 kg ai / ha.