- In this method, weeds are controlled by chemicals, referred as weedicides or herbicides. This practice is based on the principle of selectivity, killing only one kind of plants.
- These chemicals may kill or may greatly inhibit growth when applied in proper dosages at pre or post- emergence stage.
- Pre emergence herbicides like diuron, atrazine, fluchloralin etc. are applied to the soil prior to emergence of weed seeds/ seedlings by broadcasting, band application, soil incorporation or spray on soil surface (Plate 3.1).
- Post emergence herbicides such as glyphosate, paraquat (Plate 3.2) are applied with the addition of surfactant, after the emergence of weeds.
- Use of herbicides to reduce weeds under the trees is simpler method that often lowers the over-all impact on the environment.
 Plate 3.1: Application of pre-emergence herbicide (Note: Tree trunk is protected with black polythene covering)  Plate 3.2: Application of paraquat for weed control in apricot (Plate 3.2a); Killing of weeds 5 days after application (Plate 3.2b).Mango – Diuron – 6.67 to 8.9 kg/ha, Bromacil – 6.67 to 8.9 kg/ha
Banana – Alachlor 9 lit/ha – pre-emergence, Oxyfluofen – 600 – 800 ml/ha – pre-emergence
Citrus – Artazine – 2.5 kg/ha – pre- emergence, Diuron – 2.4 kg/ha – pre- emergence, Paraquat (Gramaxone) – 1.5 lit/ha – post-emergence
Grapes – Diuron – 3 – 3.5 kg/ha – pre-emergence, Atrazine – 4kg/ha – pre-emergence
Sapota – Bromacil – 3 kg/ha – pre-emergence, Diuron – 4.0 kg/ha – pre-emergence
Pineapple – Bromacil – 2kg/ha - pre-emergence, Alachlor – 4.5 lit/ha
Strawberry – DCPA 8 lb + Chloroxuron 4 lb/ac, Diphenylamide 4 lb/acre
Advantages:
1. The weeds controlled or killed while the soil remains undisturbed.
2. Prevents injury to the trees caused by rodents by destroying their harboring places.
3. Prevents injuries to the plants and roots which may occur due to disking.
4. All the cultural operations can be carried out easily in absence of weeds. Harvested fruits can be collected easily.
5. Harvesting of the fruits can be done easily.
- Some varieties of apple and pear are more sensitive to mild herbicides than others. For instance, Gala and Golden Delicious apples and all pears seem to be more sensitive than other fruits to 2,4-D, which when leached into the root zone. In these examples, you should take care not to apply, then irrigate the product into the root zone within 10-14 days after application
- Cherries and other "stone fruits" are generally less tolerant of soil active herbicides, and have many fewer safe, registered product choices. Simizine can cause serious symptoms on stone fruits when applied in many north-west facing orchard soil and irrigation situations.
- The most common and serious damage occurs on young fruit trees when unprotected bark is contacted by concentrated doses of glyphosate type products. However, this is does not mean that these products cannot be used in young orchards,
- Young trees have shallow root systems, and most of their roots are under the herbicide treated area. They may become highly exposed to root active herbicides that leach into the upper foot of soil.
- Soil Factors: These are the same well-known considerations used with many herbicides and crops. Organic matter and increased binding sites that come with finer soil texture are major soil qualities that hold potentially mobile herbicides in the upper 2-4 inches of soil, controlling weeds rather than affecting the fruit tree.
- Soil residual, potentially mobile, and actively taken up by roots. These tend to be the older, cheaper, and highly effective products that are often the foundation of a weed control combination. Examples include simizine, diuron, terbacil, and, to a lesser extent, norflurazon and dichlobenil. All very good and useful herbicides, but may be slightly to highly hazardous to fruit trees.
- Soil residual, not very mobile, and not likely to be transported in significant levels into the tree. Examples of these include oryzalin, napropamide, pronamide, pendimethalin, oxyfluorfen, and isoxaben. These products are more or less effective, but often need to be used in combinations to increase the weed control spectrum. They are more likely to fail if application directions are not followed very carefully.
- Contact, systemic, not soil active. The usual list: glyphosate or sulfosate products. These tend to be an important part of the mature orchard weed control program, and very useful for the suppression of tough perennial weeds. Contact systemic, somewhat soil active: 2,4-D.
- Contact, not very systemic, not soil active. Paraquat, which is used very effectively as a "chemical hoe" in young orchards..
Herbicides considerations:
- Read manufacturer’s instruction prior to application of herbicides for proper use (Plate 3.3).
 Plate 3.3: Manufacturer,s instructions on label  Plate 3.4: Careful application of herbicides avoiding direct drifting of spray on tree trunk.
- Herbicides must be used with care and they should be used as per recommended dose, otherwise it may cause damage to the plants (Plate 3.4).
- Use special nozzle for herbicides application to minimize spray drift and allow low pressure spraying (Plate 3.5). They come in several sizes with capabilities to apply a range of spray volume.
- Weed behaviour as affected by various crop husbandry practices, orchard management should be recorded.
 Plate 3.5: Knapsack sprayer with special nozzle for herbicide application
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