Weed Management in Horticultural Crops

WEED MANAGEMENT IN FRUIT CROPS

Tropical and Subtropical fruit crops:
I. Mango: Mango (Mangifera indica L.) occupies major area under fruits in the country. It is adaptable to a wide range of soils and climatic conditions provided severe and recurring frosts in winter do not endanger the young trees (Anon., 1980). There are numbers of varieties grown in India and some are of export quality. Veneer grafting and stone grafting are found to be the best method for mango propagation. The major monocot weeds that occur in mango orchards are Cynodon dactylon and Cyperus rotundus and dicot weeds are Bidens pilosa, Tridax procumbens and Phyllanthus maderaspatensis.

Control:

1. Hand weeding:
Usually, manual method of weed control is adopted at this time due to young nature of mango plants by employing women labour. They use small hand tools (khoorpi) for removing weeds in basins and between rows of plants.
2. Mechanical method:
When the orchard comes of age between 8 and 10 years, mechanical method of weeding by using bullock drawn implements or tractors and tillers with special weeding tools attachments are employed for effective weed control. The type and nature of tools used in mechanical method depend upon the row spacing adopted for orchard. And in an average type of mango orchard, three to four ploughing (machine or bullock drawn) are enough in a year.
3. Cover cropping: Cover cropping is another practice followed in mango orchard to suppress the growth of weeds, to bring additional income to the grower until the trees begin to bear and improve the health of trees if the intercrops grown are of right type. The recommended intercrops in mango orchards for summer season are bottle gourd, bitter gourd, onion, chilies, cowpea, black gram and green gram. For winter season, the intercrops suggested are peas, turnip, cauliflower, carrot, radish and gram.
4. Chemical control: Herbicides have been used to some extent in mango to control weeds. Application of Paraquat (3.0kg a.i./ha) or Diuron as pre-emergent treatment at 6.67 and 8.9 kg/ha gives good control of weeds in mango. Or Bromocil and Dalapon were also effective for controlling dicot and monocot weeds respectively. One spray of Atrazine or Diuron at 2.0 kg a.i./ha as pre-emergent treatment to soil and one spray of Paraquat as post –emergent spray on weeds at 3.0kg a.i./ha have been found effective for controlling both monocot and dicot weeds in one to five years old mango orchard.

II. Banana: The banana crop is sensitive to grasses especially in the early stages of their growth compare to herbaceous dicot weeds. The major monocot weeds of banana fields are Cyperus rotundus, Cynodon dactylon, Digitaria marginata, and Eleusine aegyptium, and the dicot weed are Euphorbia spp, Polygonum plebejum, Portulaca oleracea, and Mimosa pudica.

Control:

Banana crop has superficial root system and thus heavy machinery for its cultivation must be avoided. It therefore, becomes imperative to think other methods of weed control for this crop.
1. Hand weeding: Manual method of weed control by women labour using hand operated tools is the common method of weed control.
2. Mulching: Mulching appears to be another effective method of weed control. Generally, organic mulches like dried leaves and inorganic mulches like black polythene are used.
3. Cover cropping: Growing cover crops to suppress weeds is also another way of controlling weeds in this crop. Inter cropping with ginger, cowpea, colocasia and tapioca in various varieties of banana have been reported.
4. Chemical method: Herbicide have been used to weed control in banana. In banana good control of both grassy and broad leaf weeds for 4-5 months with there pre-emergent spray of diuron at 2.0 kg a.i./ha. Paraquat at 1.8 kg a.i. /ha was used as a post emergence spray on 6-9 inches tall weeds in banana and control them for two months. Herbicide application was found to be more economical than hand weeding (6 hand weeding per year were necessary in banana crop.

III. Pineapple: The structure of pineapple plants with radical leaves allows much of the sunshine to fall underneath and around the plants resulting in the growth of sun loving perennial grassy weed especially in the first 6 months from the date of planting. The predominant weeds during this time are Cyperus spp. Cynodon dactylon and Digitaria marginata among monocots, and Lagasca mollis, Portulaca oleracea and Mollugo pentaphylla among dicots.

Control:

1. Hand weeding: Due to thorny nature of pineapple leaves, manual weeding is extremely difficult. The spaces between inter-rows and plants are weeded by mans and women labours using hand operated implements like khurpi (Hand hoe) and cutlasses. But weed control is not satisfactory in this method.
2. Mechanical weed control: The mechanical weed control using spade is done by men labours when earthing up operation is done to cover the shallow expose pineapple plant after 2-3 months of planting, especially in the hill grown pineapple. Even in plains, earthing up becomes necessary as pineapple plants need irrigation once a week or 10 days.
3. Cultural method: Mulching with black polythene is a very effective method of weed control especially in Hawaii Islands. In our own country, this method is limited to very small areas. Growing intercrops in between rows of pineapple is not popular.
4. Chemical method: chemical weed control using herbicides holds promise in pineapple crop. Excellent control of both monocot and dicot weeds in pineapple var. kew with a combination of Bromocil and Diuron at 2.0 + 2.0 kg a.i./ha when given as pre-emergent treatment. The frequency of application this combination treatment had to be increased to three to four times under such conditions to get year round control of weeds. Herbicides treatment increased the yield in pineapple compared to hand weeded plots. Bromacil at 3.0 kg/ha as pre-emergent spray, fifteen days after planting of pineapple, to be effective for controlling weeds up to 90 days. Very good control can be achieved with wide spectrum of weed flora in pine apple plots treated with Diuron at 2.0 kg a.i. /ha.
Application of Glyphosate at 1.5 kg/ha along with one hand weeding was most effective control of predominant weeds such as Digitaria marginata, and Eleusine indica among monocots, and Galinsoga parviflora, Ageratum cozyzoides and Biden pilosa among dicots.

IV. Grape: Grape (Vitis vinifera L.) vine is grown in West and South India especially in Maharashtra and Andhra Pradesh, to a great extent. The varieties gown are Anab-e- Shahi and Thomson Seedless. The grapes are grown on different training systems depending upon the varieties and the purpose for which they are grown. These different systems allow the growth of various types of weeds. In Bower system, soon after pruning of grapes, there is lot of sunshine underneath which allows the growth of Cyperus rotundus and Oxalis corniculata. After sometime, the vegetative growth of grape increases and shades the underneath space with result Polygon plebejum, Euphorbia geniculata, Amaranthus viridis, Portiulaca oleracea, Oxalis sp. And Mullugo pentaphylla among dicots and Digitaria marginata, Eleusine indica, and Setaria glauca among monocots come up. In Trellis system of training, plenty of sunshine is available for weeds to grow around and Cynodon dactylon is the major weed.

Control:

Control of weeds in grape is very important to maintain the yield and quality levels as it is a commercially important crop.
1. Hand weeding: Euphorbia geniculata and E. hirta, which appear as major weeds, carry fungal and insect pests and act as alternative hosts. The usual method of weed control is manual by employing women labour. They use khurpi, a small hand operated implement, to remove the weeds.
2. Mechanical method: In mechanical method of weed control bullock drawn implement is very common in Maharashtra. In scientific orchard management, motor run tractors and power trillers are used to cultivate the inter rows of grape. But in young orchards, the root system of grape being shallow, mechanical methods using machinery becomes difficult. In such cases, usage of spade for hoeing is preferred.
3. Mulching: Mulching with inorganic materials like black polythene film and organic materials like sarkanda, wheat and rice straw, sugar cane trash, dried leaves and saw dust have been advocated for conserving soil moisture and fostering rapid growth of plants. Sarkanda was found to be the best mulch for grape in Punjab and black polythene in Tamil Nadu.
4. Cover cropping: The general cover crops grown in grape orchards are cowpea, French beans, cucurbits, sun hemp and mung.
5. Chemical weed control: Chemical weed control using herbicides has been tried in grape by several workers. These worker have used either Simazine, Atrazine, Diuron, Dalapon, Oxyflurofen, Paraquat, or Glyphosate. Except Paraquat and Glyphosate, which were used as post-emergent sprays, all other herbicides were used pre-emergent to weeds. One spray of Atrazine or Simazine or Diuron at 2.0 kg a.i./ha as pre-emergent spray followed after six months by two post-emergent sprays of Paraquat at 2.0 kg a.i./ha at three monthly intervals for grape cv. Banglore Blue. Oxyflurofen at 1.0 kg a.i./ha as pre-emergent spray and Glyphosate at 3.0 kg a.i./has post-emergent spray proved very effective for controlling weeds for four and six months respectively in grape cv. Anab-e-Shahi. Herbicides in mulched vineyards have also been tried successfully.

V. Papaya: The important monocot weeds that occur in papaya field are Cynodon dactylon, Cyperus rotundus, Eleusine indica, Chloris barbata and Digitaria marginata. The dicot weeds are Parthenium hysterophorus, Lagasca mollis, Croton bonplandianum, Euphorbia geniculata, Phyllanthus niruri and Evolvus alsinoides.

1. Hand weeding: The main method of weed control practiced in papaya is by employing women labour to remove the weeds manually by using khurpi.
2. Mechanical method: As papaya has shallow root system, use of heavy machinery to plough the interspaces to reduce the intensity of weeds in not safe. Thus, spades are used for hoeing in the basins. Even shallow ploughing by bullock drawn implements can be done.
3. Mulching: The old dried leaves and other organic materials are used for mulching in the basins of papaya.
4. Cover cropping : growing cover crops in papaya orchards is another way of controlling weeds. When papaya grown as a main crop, low growing vegetables like chillies, onion and tomatoes can be grow as intercrops for about six months with advantage. Afterwards, the tree grows bigger and shades the underneath ground and makes it impossible to grow any vegetables.
5. Chemical control: Use of herbicides to control weeds in papaya is not so common the Fluchloralin or Alachlor or Butachlor at 2.0 kg a.i./ha as pre-emergent treatment soon after transplanting of papaya seedlings, controlled all weeds including Cynodon dactylon and Cyperus rotundus for a period of four months under sandy loam soil conditions. Chemical weeding was found economical than the conventional hand weeding. For good control of monocot and dicot weeds with Diuron and Ametryn (2.0 and 4.0 kg a.i./ha respectively) applied 3 months after planting of papaya followed by repeat application of the same every two months.

VI. Citrus: The predominant weeds of citrus fields are Cynodon dactylon, Cyperus spp., Digitaria marginata, Eleusine indica, Setaria spp., Imperata cylindra among monocots and Amaranthus caturus, Biden pilosa, Lagasca mollis, Acanthospermum hispidium, Euphorbia Spp., Borreria articularis and Evolulus alsinoides among dicots. `

Control: Weeding at regular interval to reduce the competition of weeds with trees and to avoid harbouring of dangerous fungal and insect pests, to which the citrus trees are highly prone, should be carried out.

1. Hand weeding: Various methods of weed control are practiced in India in citrus orchards. In young citrus orchards, manual method of weed control using hand operated implements like khurpi and cutlasses is very popular with growers. Both women and men labours are employed for this purpose.
2. Mechanical method: In established orchards, cultivation and hoeing helps in eradication of weeds and conservation of soil moisture. In closely planted orchards, ploughing by bullock drawn or motor run implements becomes difficult. In such cases, cultivation in done by hoeing with the spade. Three to four ploughing in a year in closely planted orchards are enough for an average type of citrus plantation. Heavy machinery like tractor and power tillers must be avoided for ploughing in citrus orchards because of their shallow root system which can damage during the ploughing operation.
3. Mulching: Mulching the citrus basins with organic and inorganic materials is another common method of controlling weeds.
4. Cover cropping/ intercropping: Growing cover crops to reduce the density of weeds in the inter-rows of citrus plants is also popular with growers in our country. Intercropping also brings more money to the grower and improves the health of the trees if the intercrops grown are of right type. For summer season, vegetables like tinda, bottle gourd, onion, chillies, mung, cowpea and cotton are recommended for growing in 3 to 4 years old citrus orchards. In winter season, vegetables like pea, turnip, cauliflower, carrot, radish, and gram are grown. Wheat and maize as intercrops in citrus orchards. Intercropped citrus with green manure crops and observed that they were helpful in maintaining organic matter content and moisture in soil besides improving N content to a great extent.
5. Chemical weed control: Chemical weed control using herbicides has been successfully tried in citrus. Bromacil and diuron combination at 2.0 kg a.i./ha each to be superior to single spray and got weed control upto 4 months. Gesatop application at the rate of 5.0 kg/ha and casagard at 4.0 kg/ha controlled both monocot and dicot weeds very effectively. Pre-emergence herbicides such as monouron and diuron at 1.5 and 2.5 kg/acre respectively cotrolled the weeds effectively in sweet orange orchards. Pre-emergent application of diuron at 6.67 and 8.90 kg/ha can control all weeds in citrus.

VII. Sapota: The predominant weeds of sapota fields are Setaria glauca, Digitaria marginata, Andropogn sp., Heterogon contortus and Cymbopogon caesius among monocots and Oxalis corniculata among dicots.

Control: The removal of weeds in young sapota orchards is done manually by labours using small hand operated implements.

1. Mechanical control: In established orchards, with enough space in between plants, the removal of weeds and the loosening of the soil is done by ploughing or harrowing once or twice a year either by bullock drawn implements or by motor run tractors or tillers.
2. Inter –cropping: Inter-cropping of vegetables, viz., cowpea, French beans and peas in inter-rows and ginger in basins may also be taken up for the first six to ten years.
3. Chemical control: Bromacil and diuron combination at 2.0 kg a.i./ha to be very effective for controlling weeds in established sapota orchards for a period of 4-5 months.

VIII. Guava: The problematic weeds of guava fields are Cynodon dactylon and Cyperus rotundus among monocots and Bidens pilosa, Tridax procumbens, Acanthospermum hispidum and Lagasca mollis among dicots. As reported earlier, Cynodon dactylon caused 50 per cent reduction in plant height of guava.

Control:

1. Hand weeding: The young guava orchards are weeded manually by women labour using hand operated implements.
2. Mulching: In established orchards, mulching with in organic and organic materials have been tried. The dried leaves are usually mulched into the soil in the basins soon after one or two rains. The growing of green manure crop during the rest of the year are recommended.
3. Chemical control: 2,4-D alone at 3.0 kg/ha or 2,4-D(2.0 kg/ha) in combination with gramoxone (1.5 l/ha) to be the most effective herbicides for controlling weeds in established guava orchards.

IX. Litchi: Litchi (Litchi chinensis Sonn.) orchards need atleasts 3 to 4 cultivation in a year to keep them weed-free. As litchi trees have shallow roots, deep tillage must be avoided. The growing intercrops like legumes during pre-bearing stage of litchi would give good income to the grower besides improving the health of trees. But the roots of intercrops should not be allowed to compete with the main crop for nutrients.