Weed control in orchards is most essential around the tree bases, called tree rings. Sometimes these rings are joined by weeding in continuous 1.5 to 3 m strips down the tree rows. Here the weeds, in addition to competing with the growth of trees, interfere with fruit picking, tree pruning, and other cultural operations.
The tree bases are not easily accessible to mechanical weeding. Here herbicidal control is more feasible. The herbicide treated, weedfree rings can be covered with black polythene sheets to prevent further weed growth and conserve soil moisture at the same time.
Following are the common herbicides found useful in orchards in different countries, including India. In general, a herbicidal control operation in the orchards should be limited to the dormant and non-bearing stages of the trees to avoid possible damage to their fruiting shoots.
Paraquai/Diquat (0.1% Spray):
Paraquat and diquat do not injure non-green, woody stems of fruit trees. Therefore, these herbicides can be sprayed in the tree rings, with limited precautions, to destroy the young weeds. Repeat herbicide applications are needed to deal with the regrowth of the weeds. Paraquat is somewhat more effective on grasses than diquat.
Simazine/Atrazine (1-2 kg ha-1):
These herbicides are applied to the ground after initial removal of the existing weeds by physical means, to obtain residual control of weeds for some extended period. These are found selective to apple, banana, grapevine, pear, and some other deciduous trees.
Established apple and pear are tolerant to simazine up to 5 Kg ha-1, and raspberry up to 4 kg ha-1. At 0.75 kg ha-1, simazine has been found selective also to one year old apple plants in the nursery. In vineyards, atrazine can be used up to 4 kg ha-1. Its band application at 2 kg ha-1, combined with inter-row tillage, is often more beneficial than its overall application at higher doses.
Bromacil (3-4 kg ha-1):
In two years’ or older apple, peach, sapota, and citrus orchards, directed and spot treatments with bromacil in the tree rings and around will control grasses and nutsedge, without damage to the trees. Also, at 3 kg ha-1, preemergent bromacil can provide effective weed control in pineapple for about 4 months.
Terbacil (2-10 kg ha-1):
Terbacil is used for ring weeding in two years’ or older apple, peach, and citrus orchards as directed spray. Use lower doses against annual weeds and higher rates against the perennial ones.
Lenacil (2-4 kg ha-1):
Lenacil is found useful for preemergence weed control in raspberry and strawberry. It can also be applied mixed with simazine (0.5 kg ha-1) or terbacil (0.5 kg ha-1) for obtaining wide- spectrum weed control.
Diuron (1-2 kg ha-1):
Diuron is a very effective preemergence herbicide for the control of annual weeds in apple, pear, citrus, banana, sapota, pineapple, and grape. The grape vineyards can tolerate Diuron up to 3.5 kg ha-1.
Dalapon (1% spray):
Dalapon is recommended for ring weeding the four years’ or older apple and pear orchards. Dormant citrus and vineyards can also be treated with postemergent dalapon. In either case use only directed sprays of the herbicide.
Amitrole (4-6 kg ha-1):
Directed sprays of Amitrole are used to destroy annual weeds in four years’ or older apple, pear, and citrus orchards without anticipating any damage to the fruit trees. It is often combined with simazine or diuron for obtaining simultaneous, residual weed control.
Glyphosate (1-2 kg ha-1):
Glyphosate can be the choice herbicide for the control of perennial weeds in orchards, in general. It should be applied as a directed spray away from the tree bases.
Alachlor (1-2 kg ha-1):
Alachlor has been found a very successful preemergence herbicide in India for banana plantations. In research plots it provided perfect weed control for about 3 months which doubled the fruit yield.