Chilli

Weed Management

Common weeds in chilli

• Grasses,
• Sedges, and
• Broad leaved weeds.

Grasses

• Grasses are the monocots with two ranked leaves that are usually long, narrow and upright with parallel venations.
• The stems are more or less round in shape, possess nodes, internodes are generally hollow with scattered vascular bundles.
• Leaves have ligule and auricle at the junction of lamina and leaf sheath.
• Some of the grassy weeds are as follows:
  • Cynodon Dactylon V.N: Garika (Bermuda grass) Extensively creeping perennial grass with under ground rhizome.
  • Dactyloctenium aegypticum V.N: Nakshatra gaddi (Crow foot grass) Spreading and ascending annual grass rooting at lower nodes.
  • Echinocloa Crusgalli V.N: Ooda (Barnyard grass) A trouble some annual weed.

Sedges

• Sedges are very similar to grasses but have three ranked leaves.
• The stems are usually triangular and they won't possess nodes and internodes.
• Several species have modified rhizomes which are used for food storage and propagation.
• Some of the sedges are given below:
  • Cyperus deformis V.N: Tunga (Common sedge/ Annual Sedge)
  • Cyperus rotundus V.N: Tunga (Purple nut sedge/nut grass) Erect Rhizomatic stem tuber forming perennial.

Broad Leaved Weeds

• Broad leaved weeds are usually dicots with tap root system. The stem has branches and leaves with a net venation.
• Some of the broad leaved weeds are:

Salient Features of a Weed

• The germination of weed seeds is early and the weed plants grow fast as compared to crop plants.
• The viability of weed seeds is very long and seeds are able to germinate intermittently many times in a year and in some cases year after year.
• Some of them can retain their viability for 10,20 or up to 40 years or so.
• The seeds of Chenopodium album (Goosefoot) were found to have germination ability after having been buried in the soil for 20 to 40 years.
• Nelumbo nucifera (Lotus) seeds were also able to retain viability for several years.
• Some weeds have special structures like wings and spines which help in their dispersal from one place to another by wind or by animals and even by human beings.
• Both weed seeds and plants possess unusual adaptation to the adverse environmental conditions.
• Weeds have ability of produce profuse flowers in short period and have a very high percentage of seed setting that results in large number of seed formation.
• Many weeds propagate vegetatively and spread rapidly under adverse conditions.
• The well known weed is Cynodon dactylon (Bermuda grass) having rhizomes, their dispersal is effected by the cultivation of the soil which helps to divide and spread portions of the rhizomes.
• Many weeds having protective devices viz., spines and thorns, stiff hairs and sticky materials that protect them from damage caused by men and animals.
• Many weeds having deep tap root system, and while growing they compete with crop plants for moisture and nutrients.

Harmful Effects of Weeds

• Growth rate of weeds is very high
• Weeds normally have high photosynthetic efficiency. The crop production is adversely affected by weeds in following ways.
• Weeds are fast growing, therefore, they compete with crop for solar radiation, water, nutrients and space.
• They reduce yield, quality and marketability of vegetables.
• Weed infestation increases cost of cultivation as control measures require labours, materials, equipments and management.
• Certain weeds provide hiding place for insect-pests and act as host plants for certain pathogens. Insects such as aphids, thrips, weevils, and flies survive on wild mustard (Brassica kaber), wild carrot (daucus carota), ragweed, pigweed (Amaranths retrofleux), etc., Pathogens of black stem rust of wheat harbour on wild oats, and perennial grasses.
• They block the drainage and impede the flow of water in irrigation channels.
• Some weed plants secrete harmful chemicals that may have harmful effects on crop plants, soil, human being and livestocks. Skin eruptions have also been found allergic reactions by some weeds. Pollen grains inhalation may cause disorders in respiratory tract. Lathyrus sativa (pulse consumption) causes posterior paralysis in human being due to a compound, B-amino propionitrite. Parthenium hysterophorus (congress grass) causes skin allergy with body contact.
• The pollens of Ambrosia artemisifolia (ragweed) when inhaled, causes hay fever.

Methods of weed Control

Cultural Methods

• Timely sowing of chilli gives vigorous crop growth quick canopy coverage - suppress weeds.
• Band or pocket application of N-fertilizer to chilli reduces the nutrient availability for weed growth.
• Sowing certified seed.
• Adopt furrow method of irrigation.
• Raising chilli in paired rows and utilising the interspace effectively by cultivating intercrops like onion, greengram, bhendi etc., is found useful not only to reduce the incidence of weeds but also to obtain additional income per unit area.
• Proper crop rotation is highly useful for control of perennial weeds.
• Mulching not only reduce weeds but also evaporation from soil.

Mechanical Control

• Deep ploughings, digging and removal of rhizomes or, stolong os perennial weeds before sowing.
• Periodical harrowings reduce weeds and evaporation losses of moisture.
• For direct seeded crop and transplanted crop at 25-30 days after sowing and after transplanting respectively one intercultivation with blade harrow followed by line weeding within the rows is necessary. Subsequent intercultures at 10-12 days intervals till full coverage of land by crop should be given.
• If the crop is sown on ridges as irrigated crop the interculture invariably followed by 3-4 days after each irrigation preferably with a planet junior hoe.
• While inter cultivating the crop deep cultivation should be avoided to avoid damage to roots and also loss of moisture from deeper layers.

Chemical Control

Preplanting

• Soil incorporation of Fluchloralin (Basalin) at 2.0 ltr/ha as pre-sowing application upto 5cm deep is very useful to control mostly annual grasses and some broad leaved weed.
• Pre sowing application of Nitraline, Trifluralin, and Dinitramine at 1.0 kg/ha each.
• Alachlor 5.0 kg/ha is very effective
• For controlling Cynodon, TCA at 5kg/ha as preplanting treatment is best.

Pre-emergence

• Trifluralin 0.75 kg/ha and Nitralin 3kg/ha can control most grasses and sorghum halopense.

Post Emergence

• Post planting herbicide : Basalin
• Dose 2-2.5 letres/ha or 0.8 to 1.0 letre/acre
• Time of spraying : One week after planting
• Method of spraying : Spray should be directed in between the crop rows. Spray on weed free land in between crop rows. Immediately after spraying run a blade harrow for thorough mixing with the soil.

Precautions while handling herbicides

• Recommended dose of herbicides should be applied.
• Thin film of water should be kept in the field before the chemical application.
• Irrigations and draining the water should not be done upto 3-6 days in chemically treated plots.
• Herbicides should be applied at the recommended time only
• Avoid spraying in severe sun or when the soil is dry for getting better results.
• Sprayers and sprayer parts should be thoroughly washed after using the herbicides, if the same equipment is intended for spraying the pesticides.
• Specific nozzles recommended for herbicides only have to be used.
• Better use high volume sprayers under low pressure to avoid drift and carry over of the particles in the event of using herbicides in the standing crop.
• Don't mix two herbicides that are incompatable, consult weed specialist in this aspect.
• Containers should be kept out off reach to children.
• Herbicides should be transported in tightly closed containers.
• They should be kept away from food and feed stuff in the store.
• The herbicide contamination with seed, fertilizer, fungicide and insecticide should be avoided.
• Used containers should be discarded and burried.
• Inhalation of spray must, contact with skin or eyes or clothing should be avoided.
• Never blow the clogged - nozzles with mouth.
• Don't smoke or eat while spraying.