Correct Methods for Using Herbicides in Woody Flower Nurseries

Weed control in nurseries has always been a difficult problem in production. At present, most weed control methods are manual pulling, cultivation, plastic film mulching, etc. In fact, the simplest and most effective method in woody flower nurseries is to use herbicides.

For one- and two-year-old seedlings, herbicides with relatively high safety for the seedlings can be used before weeds germinate. For example, use 2.5% nitrofen wettable powder at 400-600 g per mu, mix with 40 kg per mu of sifted dry fine soil and broadcast, which can control annual Asteraceae and Poaceae weeds, with a effective period of up to 1 month. In addition, some herbicides can also be used for stem and leaf treatment during the vigorous growth period of weeds, such as 12.5% haloxyfop emulsion concentrate at 40-80 mL per mu, add 40 kg of water, prepare a medicinal solution and spray, which can effectively control many annual grass weeds. If there are many dicotyledonous weeds in the nursery, 10.8% high-efficiency haloxyfop emulsion concentrate can also be mixed with 3.5% quizalofop emulsion concentrate at a ratio of 1:1, and targeted foliar treatment can be carried out between seedling rows, which can effectively control annual monocotyledonous and dicotyledonous weeds without adverse effects on seedling growth.

For seedlings more than two years old, nitrofen or 50% prometryn wettable powder at 100-200 g per mu can be selected, mixed with 40 kg of sifted dry fine soil and broadcast, which can control weeds such as Alopecurus aequalis, Poa annua, Leptochloa chinensis, Capsella bursa-pastoris, Echinochloa crus-galli, and Digitaria sanguinalis. For large seedlings and young trees with higher trunk bases and secondary transplanting, 10% glyphosate aqueous solution at 750 mL per mu and 40% atrazine suspension concentrate at 150-250 mL per mu can be used under the tree canopy, prepared into a medicinal solution and sprayed on the soil surface.

Herbicides can be selected according to differences in stem and leaf morphology. Some broadleaf seedlings such as Camellia japonica, Michelia figo, Magnolia grandiflora, and Ligustrum lucidum can also be treated on stems and leaves with directed spraying of glyphosate; other broadleaf seedlings such as Albizia julibrissin, Cercis chinensis, and Hibiscus syriacus cannot use glyphosate, but before germination, 24% quizalofop emulsion concentrate at 10-15 mL per mu can be mixed with dry fine soil to make dry herbicidal soil and broadcast, then the seedlings should be washed with clean water. The effect of controlling annual monocotyledonous and dicotyledonous weeds is good, and it is harmless to the seedlings. Generally, coniferous ornamental plants have stronger herbicide resistance than broadleaf ornamental plants. For Pseudolarix amabilis, Sabina chinensis, and Platycladus orientalis, 10% glyphosate aqueous solution at 750 mL per mu can be used, add water to prepare a medicinal solution for direct stem and leaf treatment, which can effectively kill perennial weeds such as Imperata cylindrica, Cirsium setosum, and Ixeris denticulata, and is relatively safe for the seedlings.

For safety reasons, for some relatively rare and precious flowers, such as Rhododendron hybridum and Camellia sasanqua, herbicide use in the planting beds must be especially cautious. When weeds are about 15 cm tall, glyphosate can be prepared into a 0.3%-0.4% concentration solution and applied to weed stems and leaves, which can avoid the solution touching the seedlings and causing phytotoxicity. Before weeds germinate, 25% nitrofen wettable powder at 400-600 g per mu can also be made into herbicidal soil and broadcast on the seedbed, then the herbicidal soil falling on the seedlings should be swept clean. In addition, before weeds germinate, 48% trifluralin emulsion concentrate at 80-100 mL per mu can be used, add 50 L of water, prepare a medicinal solution and spray on the bed surface, then wash the seedlings with clean water. After the water on the seedlings has dried, cover with an appropriate amount of fine soil to prevent trifluralin from volatilizing and photodegrading, which would affect the efficacy.

For Michelia figo, Camellia japonica, Ligustrum lucidum, Magnolia grandiflora, and other plants with leathery leaves and a waxy layer on the surface, as well as coniferous ornamental plants such as Sabina chinensis with aromatic resin in stems and leaves, because their herbicide tolerance is relatively strong, herbicides with relatively poor selectivity such as glyphosate can be sprayed on weed stems and leaves in clear and windless weather. For ornamental plants with thin leaves and little wax such as Prunus persica 'Duplex', Ilex aquifolium, and for Hibiscus mutabilis and Spiraea cantoniensis with fuzz on the leaf surface, because their herbicide tolerance is relatively poor, only strongly selective and highly safe herbicides such as haloxyfop can be used for stem and leaf treatment.

There are some precautions when using herbicides. In nurseries, when using 65% glyphosate soluble powder, micro ultra-low-volume spraying is generally not used, to prevent phytotoxicity to seedlings caused by liquid drift. 10.5% high-efficiency haloxyfop emulsion concentrate and 23.5% goal emulsion concentrate can be mixed or used alternately, which is beneficial for controlling monocotyledonous and dicotyledonous weeds in nurseries.