Herbicides screening for ornamental plant production (nursery stock, cut flowers and wallflowers)

The Problem:

This project will build on results from HNS PO 192 to refine and demonstrate promising treatments for important cut-flower crops and wallflowers and to add two additional crops to the programme.  Season long programmes will be developed for container nursery stock using a combination of new (HDC H22 and HDC H25) and currently authorised herbicides. Additional areas of work will be to compare treatments for liverwort control for efficacy and longevity compared with Mosskade and to test new herbicides (including HDC H22 and HDC H24) for crop safety on field grown hawthorn when used on the dormant crop.

Benefits to industry:

For cut flower growers successful completion of the project would produce a number of benefits for the industry:

• Labour savings, as hand-weeding would be reduced;
• Risk of crop damage minimised;
• Better cost-effectiveness and pesticide audit, and environmental benefits, as unnecessary or ineffective herbicide applications would be avoided;

The UK outdoor flower crop area is ca. 800 ha. With herbicides costing from about £100 per ha and an application cost of about £20 per ha, one herbicide application across the area would cost the industry around £96k per annum. With improved knowledge, either the cost of ineffective treatments would be saved, or treatments that were effective would result in labour saving (reduced hand weeding) and a better quality crop.

For container nursery stock growers hand weeding is costly, estimated as being up to 30-40 times more expensive than herbicide programmes.  With labour accounting for around 40% of container production costs, hand weeding alone can account for 10% of this cost.  Hand weeding, as well as being costly, inevitably leaves some seed behind as a source of contamination for the next stage of production.

Virtually all container nursery stock growers could benefit from this work as weed control is a common problem across the industry.  Willowherb groundsel are particular problems and the loss of Ronstar 2G and restrictions on the use of Butisan S will make control more difficult to achieve.  In order for growers to take up this work authorisations would be required for HDC H22 and H25. Work is already underway to achieve a label recommendation for ornamentals for HDC H25.  Work is also underway to achieve registration in the UK for HDC H22, once that is obtained an EAMU can be applied for. 

The control of liverwort is a longstanding problem in pots, beds and paths for the container nursery stock industry.  The recent introduction of the physical acting control Mosskade has eased the situation but growers have found it is less effective during the summer and relatively short lasting.  It is also an expensive treatment to use on a large scale including paths and beds.  Therefore further treatments are sought that could complement the use of Mosskade offering more persistent and economical control although they may not be applicable in all fields of use.

There are a number of treatments that could provide liverwort control in different situations of use. It would be extremely valuable for the industry for all these products to be critically assessed alongside each other and ranked for pre-emergence, contact and persistence of liverwort control.  From this recommendations could be drawn up for different situations of use (eg beds, paths or over crops, protected and unprotected)

The loss of Ronstar Liquid will impact on growers of field grown nursery stock, so the development of further safe herbicide treatments will be useful to maintain control and avoid resort to expensive hand weeding.            

Aims and objectives:

Project aim(s): 

To develop new herbicide options for ornamental plant growers in order to achieve effective, economic weed control with minimal crop damage.

Project objective(s):

1) To test 9 new herbicide treatments, alone or in combinations, for crop safety on 4 drilled flower species (sweet william, china aster, larkspur, wallflower) and 1 perennial flower species (peony).

2) To demonstrate 3 promising herbicide treatments in larger demonstration plots on growers’ holdings for sweet williams and transplanted china aster.

3) To test 6 herbicide programmes for crop safety on 40 container-grown hardy nursery stock shrub subjects when used as post-potting, late summer and winter applications to provide season long weed control.

4) To test 15 treatments (including herbicides, biocides, physical acting and commodity substances) for liverwort control, for contact and residual action when applied either in Summer or Winter.

5) To test 7 herbicide treatments for crop safety on field grown 2/0 hawthorn seedlings as dormant season treatments.

6) To communicate the results of the project to growers and the wider industry.