Xhang container hns: Use of contact herbicides in the nursery situation hns 70a September 2000




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XHANG
Container HNS: Use of contact herbicides

in the nursery situation
HNS 70a
September 2000


Project Title:

Container HNS: Use of contact herbicides in the nursery situation


Project Number:

HNS 70a


Project Leaders:

John Atwood, ADAS Park Farm, Ditton, Aylesford, Kent, ME20 6PE

Dr Jim Monaghan, HRI Efford, Lymington, Hants, SO41 0LZ




Final Report:

September 2000


Key Workers:

Tim Briercliffe, John Owen, ADAS Park Farm, Ditton, Aylesford, Kent, ME20 6PE

(Spraying, crop recording)

Shirley Foster, Carrie Hawes, HRI Efford, Lymington, Hants, SO41 0LZ

(Trial layout and weed recording)

Gail Kingswell, HRI East Malling, Kent, ME19 6BJ

(Statistical analysis)




Location of Project:

Hillier Nurseries Ltd, Ampfield, Romsey, Hants, SO51 9PA


Project Co-ordinator:

Dr Karen Girard, Hillier Nurseries Ltd, Ampfield, Romsey, Hants, SO51 9PA


Date Project Commenced:

1 July 1999


Date Project Completed:

30 September 2000


Keywords:

Keywords cont.



Chamaecyparis lawsoniana 'Ellwoods’ Gold', Chamaecyparis pisifera ‘Boulevard’, Hypericum ‘Hidcote’, Lonicera japonica 'Halliana', Potentilla fruticosa 'Primrose Beauty', Spiraea ‘Arguta’, Spiraea japonica 'Candlelight', Symphoricarpos X chenaultii ‘Hancock’, Viburnum tinus 'Eve Price', Vinca minor 'Bowles’ Variety', Flex, Butisan S, Flexidor 125, Basagran WG, Diuron Flowable, Kerb 50W, Nortron, Opogard, fomesafen, metazachlor, isoxaben, bentazone, propyzamide, ethofumesate, terbuthylazine, terbutryne, hairy bittercress, groundsel, sow thistle, common chickweed, mouse ear chickweed, willowherb, pearlwort, annual meadow grass, Sonchus oleraceus, Stellaria media, Cerastium holostoides, Cardamine hirsuta, Senecio vulgaris, Epilobium ciliatum, Sagina procumbens, Poa annua, container nursery stock, weed control, herbicides, phytotoxicity.

Whilst reports issued under the auspices of the HDC are prepared from the best available information, neither the authors nor the HDC can accept any responsibility for inaccuracy or liability for loss, damage or injury from the application of any concept or procedure discussed.


The contents of this publication are strictly private to HDC members. No part of this publication may be copied or reproduced in any form or by any means without prior permission of the Horticultural Development Council.

CONTENTS






Page No


PRACTICAL SECTION FOR GROWERS





Commercial benefits of the project


1

Background and objectives

1

Summary of results and conclusions

2

Action points for growers

4

Anticipated practical and financial benefits
SCIENCE SECTION

4







Introduction

5

Materials and methods

6

Results and Discussion

10

Conclusions

Technology transfer

References

26

28

28


APPENDICES
Appendix 1: Weed records and statistical analysis

Appendix 2: Crop scoring data and photographs


30

36















PRACTICAL SECTION FOR GROWERS
Commercial benefits of the project
This project has identified and evaluated a number of herbicides to control a range of common weeds of nursery stock, after weed emergence, over the winter period. The most effective herbicides have been determined for each of the weed species studied, to enable growers to tailor their winter herbicide programme according to their weed problems. As a result it should be possible to make substantial savings in hand-weeding costs in the spring.
Further information on crop safety is provided, adding to the information gained by previous HDC experiments.
Background and objectives
Herbicide programmes, until recently, have predominantly been used for application to container HNS over the growing season. However, development of weeds over the winter can become a serious problem especially in milder autumn periods. Late season weed build up can occur even where herbicides are applied during the growing season if the programme adopted does not fully control the range of weed species, or if weed pressure becomes too great or resistant strains occur. In these situations hand weeding is usually the only option.
The potential of a number of herbicides with contact action over the winter was identified in HNS 70 (Scott, Girard and Brough 1998), where efficacy of the chemicals was assessed first at HRI Efford, on individual weed species, in the absence of the nursery crop, and subsequently on a commercial nursery. While weed pressure was relatively low in the latter experiment for fully testing contact action, benefits from residual activity in limiting further weed build up were obtained. In addition, few phytotoxic symptoms were observed over ten HNS species included in the experiment with the majority of herbicides used.
The current research was carried out at Hillier Nurseries Ltd, Ampfield, under commercial conditions. The aim of the research was to confirm the promising contact results obtained in the earlier Efford work, to further test the safety of these herbicides over another range of HNS species during the winter period, and to improve spray contact with the weeds in the presence of the nursery crop.

Summary of results and conclusions
Trial plants of 10 nursery stock species (see below) were potted into 3 litre containers in July 1999 and kept weed-free with pot toppers until commencement of the trial:



Chamaecyparis lawsoniana 'Ellwoods’ Gold'

Viburnum tinus 'Eve Price'




Potentilla fruticosa 'Primrose Beauty'

Chamaecyparis pisifera ‘Boulevard’




Spiraea japonica 'Candlelight'

Symphoricarpos X chenaultii ‘Hancock’

Spiraea 'Arguta'

Lonicera japonica 'Halliana'




Hypericum 'Hidcote'

Vinca minor 'Bowles’ Variety'



A prepared seed mix of hairy bittercress, willowherb, groundsel, common chickweed, sow thistle, annual meadow grass, pearlwort and mouse ear chickweed was sown into each pot on 29 September 1999.


The following herbicide treatments were applied on 14 December 1999 and again on 13 March 2000 to half of the plots:


Treatment

Trade name

Active ingredient

Application rate /ha

Water volume litres/ha

Status

Note


1.

Untreated













2.

Flex

fomesafen (250 g/l)

0.9 litres

2500

1

3.

Butisan S +

Flexidor 125



metazachlor (500 g/l)

isoxaben (125 g/l)



2.5 litres

2.0 litres



1200

1

2

4.

Butisan S +

Flexidor 125



metazachlor (500 g/l)

isoxaben (125 g/l)



2.5 litres

2.0 litres



2500

1

2

5.

Basagran SG

bentazone (87% w/w)

1.65 kg

1200

1

6.

Basagran SG

bentazone (87% w/w)

1.65 kg

2500

1

7.

Diuron

diuron (500 g/l)

0.8 litres

1200

1

8.

Diuron

diuron (500 g/l))

0.8 litres

2500

1

9.

Kerb 50W

propyzamide (80% w/w)

1.7 kg

1200

1

10.

Kerb 50W

propyzamide (80% w/w)

1.7 kg

2500

1

11.

Nortron

ethofumesate (200 g/l)

5.0 litres

1200

1

12.

Nortron

ethofumesate(200 g/l)

5.0 litres

2500

1

13.

Opogard +
Flexidor 125

terbuthylazine (150 g/l) terbutryne (350 g/l)

Isoxaben (125 g/l)



2.8 litres
0.6 litres

1200



1
2

14.

Opogard +
Flexidor 125

terbuthylazine (150 g/l) terbutryne (350 g/l)

Isoxaben (125 g/l)



2.8 litres
0.6 litres

2500

1
2

Note - Approval status

1 This product can be used off-label at grower’s own risk under the Revised Long Term Arrangements for Extension of Use (2000). 2 This product has on-label approval for use.

The weed sowing was successful, producing good numbers of all weed species.



Weed counts were taken on four occasions during the period. At the time of the first herbicide application, most weeds were at the two true leaf stage, by the time of the second herbicide application, most remaining weeds were at the four true leaf stage.
The best overall weed control was achieved by Butisan S + Flexidor 125 and Opogard + Flexidor 125. Flex, Basagran SG and Diuron did not give such broad-spectrum control but were useful for specific weeds such as groundsel and willowherb. The following table summarises the results:





Hairy bittercress

Willowherb

Groundsel

Common chickweed

Sow thistle

Annual meadow grass

Pearlwort

Mouse ear chickweed

Flex

***

**

***




*










Flexidor + Butisan

***

*

*

***

***

***

***

***

Basagran

***

**

**

**

***







**

Diuron

***

**




**







*

*

Kerb










**




***




**

Nortron
















**

**

***

Opogard+Flexidor

***

***




***

***

*

***

***

*** = good control (>90%), ** = moderate but useful control (50-90%), * = slight control (<50%)
Most of the herbicides were quite slow-acting, taking several months to achieve control, suggesting that much of the activity was through root uptake rather than direct scorch. Flex and Basagran SG, however, were much faster in activity giving a rapid knockdown of susceptible weed species.
In general the same pattern of weed control was seen whether a one (December) or two (December and March) spray programme was used. For most herbicides there was little difference in weed control from applying the herbicides in 1200 litres/ha or 2500 litres/ha. However for Diuron, and to a lesser extent with Kerb 50W there was an improvement in weed control where 2500 litres/ha rather than 1200 litres/ha was used.
All of the herbicides tested were relatively safe when used as a single application to the dormant crops in December. There were just a few incidences of damage. Potentilla fruticosa 'Primrose Beauty' was stunted by Opogard + Flexidor 125. Flex caused die-back on Viburnum tinus 'Eve Price', but was safe on other evergreens as well as the deciduous species. Lonicera japonica 'Halliana' was not fully dormant and was scorched by Butisan S + Flexidor 125 and Nortron. Kerb 50W caused a growth reduction on Vinca minor 'Bowles’ Variety' and Symphoricarpos X chenaultii ‘Hancock’. Opogard + Flexidor 125 damaged both Spiraea species.
The spring application was made as the crops were starting to grow away and caused more damage. At this stage, Flex, Butisan S + Flexidor 125, Nortron and Opogard + Flexidor 125 caused unacceptable damage either from direct contact action or root uptake. Higher volume sprays tended to be more damaging. However, Basagran SG and Kerb 50W were safer causing virtually no damage from the spring treatment.

Previous experiments (HNS 70) confirmed the relative safety of Basagran SG, Diuron (at the low rates used), Kerb 50W and Nortron as winter treatments. However this is the first year of results from the use of Flex and the Opogard + Flexidor 125 mix, so some caution should be exercised before using these products widely. Butisan S and Flexidor 125 can damage some species, and the HDC weed control handbook should be consulted for crop safety tables.


Action points for growers


  • First choice for cleaning up a broad range of weeds in hardy nursery stock over the winter period should be Butisan S + Flexidor 125.

  • Where groundsel is the main weed Basagran SG is an alternative or supplement.

  • Where willowherb is the main weed Diuron is an alternative or supplement.

  • Opogard + Flexidor 125 has the potential for outstanding control of a range of weed including willowherb, but should be used with caution, pending further work.

  • Flex has potential for use as a quick knockdown of hairy bittercress, groundsel and small willowherb seedlings, but should be used with caution.

  • Application in 1200 litres/ha gave similar results to 2500 l/ha except for Diuron and Kerb 50W, where the higher volume gave better control.

  • Clean-up treatments should be applied when the crop is fully dormant. If application is delayed, Basagran SG is the safest option.


Anticipated practical and financial benefits from the study


  • Improved overwinter weed control, leading to a reduction in hand-weeding.

  • Further information on crop safety, avoiding crop losses due to inappropriate herbicide use.


SCIENCE SECTION
INTRODUCTION
Herbicide programmes, until recently, have predominantly been used for application to container HNS over the growing season. However, development of weeds over the winter can become a serious problem especially in milder autumn periods. Late season weed build up can occur even where herbicides are applied during the growing season if the programme adopted does not fully control the range of weed species, or if weed pressure becomes too great or resistant strains occur. In these situations hand weeding is usually the only option.
The potential of a number of herbicides with contact action over the winter was identified in HNS 70 (Scott, Girard and Brough 1998), in detailed research at HRI Efford, where the efficacy of the chemicals was assessed in 90 mm pots sown with individual weed species, in the absence of the nursery crop. The most promising of these herbicides were then further evaluated by ADAS in the second part of the experiment on a commercial nursery. While weed pressure was relatively low for fully testing contact action, benefits from residual activity in limiting further weed build up were obtained. In addition, few phytotoxic symptoms were observed over ten HNS species included in the experiment with the majority of herbicides used, (apart from Buddleia, included as a particularly herbicide-sensitive indicator species).
Consequently, given the importance of obtaining cost-effective weed control over the winter period, these further experiments were carried out on a commercial nursery in order to confirm the promising contact results obtained in the Efford work, to further test the safety of use of these herbicides over a range of HNS species over winter, and to improve spray contact with the weeds in the presence of the nursery crop. One of the promising herbicides (Skirmish) used in HNS 70 was no longer available, so was replaced by the nearest equivalent, a tank mix of Opogard and Flexidor 125.
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