Grower Summary. FV 372a

Transcription

1 Grower Summary FV 372a Evaluation of potential alternatives for weed control in asparagus following the loss of herbicides (continuation of project FV 372) Final 2013

2 Disclaimer AHDB, operating through its HDC division seeks to ensure that the information contained within this document is accurate at the time of printing. No warranty is given in respect thereof and, to the maximum extent permitted by law the Agriculture and Horticulture Development Board accepts no liability for loss, damage or injury howsoever caused (including that caused by negligence) or suffered directly or indirectly in relation to information and opinions contained in or omitted from this document. No part of this publication may be reproduced in any material form (including by photocopy or storage in any medium by electronic means) or any copy or adaptation stored, published or distributed (by physical, electronic or other means) without the prior permission in writing of the Agriculture and Horticulture Development Board, other than by reproduction in an unmodified form for the sole purpose of use as an information resource when the Agriculture and Horticulture Development Board or HDC is clearly acknowledged as the source, or in accordance with the provisions of the Copyright, Designs and Patents Act All rights reserved. AHDB (logo) is a registered trademark of the Agriculture and Horticulture Development Board. HDC is a registered trademark of the Agriculture and Horticulture Development Board, for use by its HDC division. All other trademarks, logos and brand names contained in this publication are the trademarks of their respective holders. No rights are granted without the prior written permission of the relevant owners. The results and conclusions in this report may be based on an investigation conducted over one year. Therefore, care must be taken with the interpretation of the results. Use of pesticides Only officially approved pesticides may be used in the UK. Approvals are normally granted only in relation to individual products and for specified uses. It is an offence to use nonapproved products or to use approved products in a manner that does not comply with the statutory conditions of use, except where the crop or situation is the subject of an off-label extension of use. Before using all pesticides check the approval status and conditions of use. Read the label before use: use pesticides safely. Further information If you would like a copy of the full report, please the HDC office (hdc@hdc.ahdb.org.uk), quoting your HDC number, alternatively contact the HDC at the address below. HDC Stoneleigh Park Kenilworth Warwickshire CV8 2TL Tel HDC is a division of the Agriculture and Horticulture Development Board.

3 Project Number: FV 372a Project Title: Project Leader: Evaluation of potential alternatives for weed control in asparagus following the loss of herbicides (continuation of project FV 372) Marc Willis Contractor: SGS UK Ltd Industry Representative: Philip Langely Report: Final Report 2013 Publication Date: 02 May 2013 Previous report/(s): None Start Date: 01 March 2012 End Date: 28 February 2013 Project Cost: 6,425

4 Headline Applied pre-emergence of spears: There is flexibility in reducing Callisto dose rate in mixtures. HDC H17 gave good initial control of groundsel and black nightshade. Gamit 36 CS would be a useful addition for groundsel and cleaver control at this timing and residue data generation will be investigated. Applied post-emergence of spears: Sencorex WG and Lentagran applied alone as split doses can be safe to the crop and effective for small weeds. Mixtures may be required for larger weeds but young crop safety can be an issue. Background Weeds in asparagus crops reduce yield and quality of spears, delay maturity and increase harvest costs. Nettles and thistles deter pickers. Some herbicides can cause damage and also affect quality. Crop Protection Companies cannot justify the cost of the development and approval process for herbicides for minor, high value crops such as asparagus. There are 9 selective herbicides for broad-leaved weed control in asparagus, all of them SOLAs (now referred to as EAMUs - extension of authorisation for minor uses). No herbicides are, or are likely to be, authorised for use during the harvest period. Asparagus is grown for up to 10 years and frequent use of the limited range of herbicides has led to a build-up of weed species that may escape control. Weed seeds are exposed where pickers disturb soil. A survey in 2004 by the Asparagus Growers Association showed that thistles, nettles, field bindweed and fat-hen were frequently occurring weeds and black nightshade, groundsel and cleavers were the most serious problems. In 2010 groundsel with partial resistance to Sencorex (metribuzin) and possibly Goltix (metamitron) was identified. In 2010 HDC Project FV 372 identified: Callisto (mesotrione), HDC H17 as potential alternatives. When applied pre-emergence of spears, both controlled groundsel and black nightshade. Callisto now has a SOLA but further work on dose rates is needed. An application for an EAMU has been requested for HDC H17 and further information on weed control would be useful. Cleavers control is a problem. Gamit 36 CS (clomazone) can only be used post-harvest and before the start of fern growth. An application pre-spear emergence is needed but the effect on quality (potentially bleaching) is not known, but there are no residues data at this timing.

5 Lentagran (pyridate) controls cleavers and fat-hen and has a SOLA for post-harvest use but information on dose rates and timings is required. This project aims: To provide a wider range of herbicides so a weed control strategy using different herbicides at different timings and years could avoid build-up of certain weed species and also avoid herbicide resistance. The specific objectives are: To further evaluate alternative new herbicides identified in FV 372 in 2010 (Callisto, HDC H17), Gamit 36CS (clomazone) and HDC H16 applied pre-emergence of spears for crop tolerance and weed control. To evaluate Lentagran (pyridate) post-harvest at different timings and dose rates for crop tolerance and control of fat-hen, nightshade and cleavers. Summary of the project and main conclusions Herbicide screening trials in 2012 were in established commercial crops (Site A, sandy loam, and B, loamy fine sand), and newly planted crowns (Site C, sandy clay loam and D, sandy loam). Pre-emergence trials Herbicide Treatments (applied in 200 l/ha water volume) Herbicide Product Active Ingredient Product l or kg/ha 1 untreated - 2 Callisto mesotrione 1.5 l 3 Callisto mesotrione 1.0 l 4 Callisto mesotrione 0.5 l 5 Callisto + Sencorex WG mesotrione + metribuzin 0.75 l kg 6 Callisto + Stomp Aqua mesotrione + pendimethalin 0.75 l l 6a Sencorex WG + Stomp Aqua metribuzin + pendimethalin 0.75 kg l 7 Gamit 36 CS clomazone 0.25 l 8 Gamit 36 CS + Sencorex WG Clomazone + metribuzin 0.25 l kg 9 Gamit 36 CS + Callisto Clomazone + mesotrione 0.25 l l 10 HDC H17 HDC H l 11 HDC H17+Sencorex WG HDC H17 + metribuzin 4.0 l kg 12 HDC H16 HDC H l 13 Sencorex WG + Flexidor metribuzin + isoxaben 0.75 kg l Treatment 6 applied at site B, and 6a applied at site A Crop Safety

6 Soils were dry at application in mid-late March, followed by wet conditions in April. There was no observed crop damage at Site B. At Site A during fern growth, there was slight stunting and chlorosis from the double rates of Gamit + Callisto and HDC H17 + Sencorex WG, with a lesser effect from HDC H16. All these symptoms had grown out by full fern development in mid-july. Weed control Site A the main weed species were groundsel, black nightshade and chickweed which began to emerge in the untreated plots not long after application. Site B main species groundsel, mayweed and cleavers. Perennial weeds (marestail and thistle) affected one corner of the trial area, making assessments difficult in a few plots. Callisto all rates gave good control of groundsel, nightshade, mayweed and chickweed during the harvest period, but with a more variable rate response at Site A. The highest 1.5 l/ha rate generally gave the best control and persistence, although mayweed control was not maintained through to the later assessment. However, the 1.0 and 0.5 l/ha rates were also effective, but may lack persistence to the end of harvest when used alone. Callisto mixes adding Sencorex WG improved groundsel control over the lower rates of Callisto at Site A, but less so at Site B. This may reflect a decline in the efficacy of metribuzin at Site B where it had been used more widely in the crop (3-4 years) compared to Site A (1 year). The grower had also noticed a drop in efficacy with metribuzin in the trial field. Persistence of mayweed control was markedly improved with the addition of Sencorex WG or Stomp Aqua. Nightshade control also appeared to benefit from the addition of Sencorex WG so that 0.75 l/ha Callisto in mixture was equal to the 1.5 l/ha rate alone. Adding Gamit improved the level and persistence of groundsel control, added a significant degree of cleaver control (80%+), but no benefit on nightshade or mayweed. Gamit applied alone confirmed good activity on groundsel, chickweed and mayweed, slightly poorer control of cleavers than expected (63%), and no effect on nightshade.

7 Cleaver control appeared to be improved in mix with both Callisto and Sencorex WG, although these are not effective when used alone. Gamit + Callisto was one of the best overall mixes in the two trials. HDC H17 the trials confirmed good activity on nightshade, groundsel, chickweed and mayweed, with some control (55%) of cleavers. However, overall activity and persistence was improved with the addition of Sencorex WG. HDC H16 this was reasonably effective on groundsel, nightshade and cleavers, but lacked persistence. Activity was better on mayweed and chickweed. If this is to be pursued, further work would be required looking at mixtures with HDC H16 to establish any benefit. Of the standard treatments included, Sencorex WG + Flexidor was surprisingly effective on nightshade through the harvest period, and slightly better overall than Stomp Aqua + Sencorex WG (Site A only). Sencorex WG + Flexidor also gave better control of groundsel, as would be expected from the history of use of metribuzin, at Site A (90%+) compared to Site B (73%). Post-emergence trials Herbicide Treatments (applied in 200 l/ha water volume) Herbicide Product Active Ingredient Dose product l/ha Timing 1 untreated Sencorex WG metribuzin 0.5 kg T1 & T2 3 Lentagran pyridate 2.0 kg T1 4 Lentagran pyridate 1 kg & 1 kg T1 & T2 5 Lentagran + Logic oil pyridate + oil 1 kg + oil & 1 kg + oil T1 & T2 6 Lentagran + Sencorex WG pyridate + metribuzin 1 kg Kg T1 & T2 T1 = early fern, weeds small T2 = 10 days after T1 Crop Safety All treatments were safe to the crop at Site D. At Site C there was initially slight (but acceptable) chlorosis from all treatments. This persisted and worsened only with the Lentagran + Sencorex WG mix to give marginal crop safety by the later assessment in early August. This site had been treated earlier (June rather than July) and the fern may have

8 been softer/less waxed compared to the second site (a small commercially treated area of Lentagran + Sencorex WG in June also showed no crop damage to the fern of a newly planted crop). Weed control Site C: main weeds mayweed, annual nettle, shepherds purse, black nightshade, fumitory, pansy, annual meadow grass and sow thistle. Sencorex WG gave excellent control of all weeds at the early assessment, with only some re-growth of nightshade and sowthistle by early August. The addition of Lentagran gave no additional benefit. Lentagran a split dose application was more effective than a single early treatment, especially on nightshade. The addition of oil gave little improvement overall, but may help with mayweed control. Site D: main weeds sow thistle, fat hen, knotgrass, black nightshade. Weeds were larger at the first application compared to Site C, and all treatments struggled to give adequate control. Sencorex was again the best product, but with the larger weeds required the addition of Lentagran to achieve any significant level of control. All Lentagran treatments were poor overall. Herbicides: Current Approval Status of products in the trials (January 2013) Herbicide active ingredient Product and formulation Company Authorised use on asparagus? isoxaben Flexidor g/l SC Landseer SOLA (was voluntarily withdrawn, now on EU list approved actives) clomazone Gamit 36 CS 360 g/l CS Belchim SOLA post-harvest, not preemergence of spears pendimethalin Stomp Aqua 455g/L CS BASF SOLA metribuzin Sencorex WG 70% w/w WDG or use the new SC Interfarm Bayer SOLA mesotrione Callisto 100 g/l SC Syngenta SOLA HDC H No

9 HDC H No pyridate Lentagran WP 45% w/w Belchim SOLA Financial benefits Without suitable herbicides, asparagus production costs could be prohibitive. Safe and effective alternatives to herbicides lost as a result of the EC Review have been found and this will benefit the industry. Labour savings, and the high cost of hand-weeding would be avoided. New actives could provide growers with alternatives for weed control. A wider range of herbicides for this perennial crop will enable a weed control strategy using different herbicides at different timings and years to avoid build-up of certain species and also avoid herbicide resistance (groundsel resistance has already been identified in some crops where there has been repeated use of metribuzin, with the potential for cross-resistance to metamitron). Residues data and EAMUs will need to be sought and this may involve additional costs, although it may be possible to obtain residues data for asparagus from another country. Action points for growers Pre-emergence herbicides There is some flexibility in reducing the dose rate of Callisto, especially when used in mixture. Mixtures will improve the range of weeds controlled and persistence through the harvest period. Reducing the dose when used alone may result in inadequate weed control. HDC H17 again gave good initial control of groundsel and black nightshade, but appeared less persistent in these trials compared to FV 372 in The addition of Sencorex WG improved control. Gamit appeared crop safe in these trials when used pre-emergence and would be a useful addition for groundsel and cleaver control at this timing. A request has been made to HDC for an EAMU (SOLA) and for the residue trials to be done. Residue tests carried out in the trials showed no detection of clomazone at early spear emergence.

10 HDC H16, whilst crop safe, does not appear to offer any particular advantage over other trial or existing products. It may be a consideration if there are problems gaining new approvals or there are other product losses. If data is available for asparagus, it would be worth including in future trials in mixtures to establish its efficacy. The lack of persistence with some treatments/weeds may have been due to the high rainfall in April and May, although residual herbicides tend to work better with good levels of soil moisture compared to a dry year. Post-emergence herbicides Sencorex WG applied alone as a split dose can give good control of a broad range of weeds, providing weeds are still small at application. The addition of Lentagran may help control larger weeds, but may also result in some crop damage to young fern Lentagran applied as a split dose can be effective and safe to the crop, the addition of oil does not compromise crop safety and may help on some weeds. However, application to larger weeds may give poor results.