The effect of pre-emergent herbicides on germination and early growth of broadleaved species used for direct seeding

Abstract

Weed control is essential for successful new woodland creation by direct seeding, particularly in the first year after germination. Currently, herbicides probably offer the most practical way of achieving this in UK conditions, although successful direct seeding offers the potential for reductions in total overall herbicide use compared with conventional establishment using transplants. There is a need to identify post‐sowing pre‐emergence herbicides that might control emerging weed seedlings without significantly affecting tree seedling germination and growth. Seed of ash ( Fraxinus excelsior ), cherry ( Prunus avium ), oak ( Quercus robur ), sycamore ( Acer pseudoplatanus ), rowan ( Sorbus aucuparia ), chestnut ( Castanea sativa ), beech ( Fagus sylvatica ), Norway maple ( Acer platanoides ), field maple ( Acer campestre ), birch ( Betula pendula ), hazel ( Corylus avellana ), dogwood ( Cornus sanguinea ), hawthorn ( Crataegus monogyna ) and crab‐apple ( Malus sylvestris ) were sown in pots in glasshouses and treated with post‐sowing pre‐emergence herbicides including diflufenican, isoxaben, lenacil, metamitron, metazachlor, napropamide, pendimethalin, propyzamide and simazine. Pendimethalin and napropamide, separately or in mixture, appeared to have potential for use on most species tested, in particular ash and sycamore. Applications to emerging seedlings were more damaging. Field trials are required to confirm these initial indications of tolerance.