PERENNIAL WEEDS - control weed threat on open swards 

DOW SHIELD - sugar beet weed control in dry conditions 

Update on Saddle Gall Midge 

Orange Wheat Blossom Midge Pestwatch 

This edition's FAQs:

- How many doses of Dursban WG may I apply to a cereal crop?

- Can I still sell Grazon 90?

And finally - Aminopyralid Stewardship 

With silage cutting being early this year and farms being short of grazing because of the drought it is important to minimize the effects of encroaching perennial weeds. When targeting nuisance perennial weeds such as docks, nettles and thistles it is important to apply herbicides when the plants are actively growing and at the correct growth stage.

Most herbicide applications to silage ground occur prior to or just after first-cut. Depending on cutting date, the quality and quantity of silage taken will vary, placing greater importance on achieving the best second-cut possible.

Perennial weeds such as docks can significantly affect both the quantity and quality of grass harvested, so well-timed herbicide applications after first cut can reap rewards for the rest of the season and even into the next spring. This is likely to be particularly so this year with recent rainfall in the western grass growing areas of the UK helping to stimulate weed growth. To optimize results, wait for 2-3 weeks after cutting for docks to regrow to the rosette stage, then apply Doxstar* to actively growing plants.

Good levels of weed control can also be achieved in grazing leys at this time of year.
Where mixed weed populations are present, including docks, nettles and thistles, Pastor* is the most appropriate product to use. Where the weed spectrum is more specific, consider Doxstar for docks and Thistlex* for thistles.

With the dry spring limiting grass growth, stock will have to graze closer to thistles leaving sheep vulnerable to orf. Getting rid of thistles in sheep pasture with Thistlex significantly reduces the spread of orf while increasing grassland productivity.

Treat weeds at the rosette stage, when they are actively growing. If stem extension is already occurring, use a mechanical topper first, and then treat regrowth when it reaches the correct stage.

Summary

• Assess remaining weed populations where first-cut silage has been taken
• Assess weed populations and plant size in grazing leys
• Where treatment is necessary, make applications at the rosette stage of growth
• Weeds must be actively growing to achieve best results
• Use Pastor for mixed weed populations
• Use Doxstar for docks
• Use Thistlex for thistles
• 7 day stock exclusion period
• 28 day cutting interval
• Excellent grass safety from all products and won't inhibit grass growth after application

Keep weeds out of grassland with Dow AgroSciences’ excellent range of herbicides.

Review Critical Success Factors for further information and guidance.

Dry soil conditions and well-waxed weeds across sugar beet growing areas are adversely affecting crop emergence and making herbicide applications difficult.

Reports from agronomists confirm sugar beet crops range from fields where full emergence is yet to take place, to well-established stands with 10-12 leaves. Crops on light land are clearly the ones suffering most from the dry soil conditions, but many crops include a range of plant sizes, caused by lack of rainfall and frosts.

Where individual plant size varies within a crop, the decision about whether to apply herbicides should be based on the balance between weed infestation and the potential impact on the smallest plants. If the population of larger plants is adequate, weed control should continue.

When used alone, applications of Dow Shield^# (clopyralid) can begin once the smallest crop plants have expanded cotyledons. If Dow Shield is applied in a programme with other herbicides, the first true leaves on crop plants must be at least 10mm long. Inclusion of Dow Shield in a programme improves activity on many weeds, such as corn marigold, groundsel, fools parsley, mayweeds and black bindweed.

A particular strength is the control of creeping thistles and volunteer potatoes.

One creeping thistle plant per square metre can cause yield losses in sugar beet of as much as 1.0 tonne per hectare. To achieve high levels of control of this competitive weed, two applications of Dow Shield are required. The first treatment should be 0.5 l/ha when thistles are at the rosette stage of growth, followed 3 to 4 weeks later by an application at 1.0 l/ha.

Left uncontrolled volunteer potatoes pose a real threat to sugar beet crops. Just one potato plant in a square metre warrants treatment to protect yields and the benefits of control will continue into following crops.

Recommendations for the use of Dow Shield in sugar beet crops are very flexible, allowing its inclusion in differing management approaches, even when volunteer potato emergence occurs over an extended period.

In traditional low-dose programmes, Dow Shield should be included at 0.5 l/ha with applications of ethofumesate and phenmedipham. Two applications are recommended, typically 7 to 14 days apart. The first treatment should be made when volunteer potatoes are between 5cm and 10cm tall.

To cover extended periods of haulm emergence particularly likely this spring, a three spray programme of 0.35 l/ha Dow Shield in conjunction with ethofumesate and triflusulfuron-methyl is recommended. The first treatment should be made when the potato haulm is 5cm to 10cm high, followed by two further applications at the same rate at fortnightly intervals. In all cases, applications of Dow Shield to sugar beet should be completed by the end of June.
 

Learn more about volunteer potatoes in sugar beet

Learn more about creeping thistles in sugar beet

Download literature and labels for Dow Shield

We have had reports of flights of adult midges in Buckinghamshire, Oxfordshire and Cambridgeshire.

Earlier this spring, Agronomists reported finding considerable numbers of bright reddy-orange larvae and cocoons in the soils, often where they had problems last year. In effected wheat crops last year, it is reported that wheat yields were depressed by as much as 1.0 t/ha overall if not more. Wheat, barley, rye and, to a lesser extent, oats, can all be affected.

Adult midges are up to 5.0 mm long with distinctive reddy-brown colouring. Over the last two weeks farmers have reported seeing midges flying above wheat crops where larvae and cocoons were found earlier. This “flight” seems to have been protracted over a number of days and is earlier than would have been expected (usually expected Mid-May - Mid June). Although easy to see above the crop (with good eyesight!), farmers have reported “sticky traps” are not always catching adult midges. A distinct “empty” cocoon can be found in the soil.

The Saddle Gall Midge life cycle includes one generation per year. Each female can lay 200 eggs, which take 7 days to develop at temperatures of 18°C. Female midges lay eggs along the veins on upper leaf surfaces, often in clusters.

Saddle Gall Midge Larvae - May 2011

After hatching, the orange-red larvae move down within the leaf sheaths and puncture a stem node. This causes characteristic transverse swellings or galls. Crop damage is most typically seen in the internode below the developing ear. This part of the stem becomes swollen, remains short and is easily broken. Affected ears remain within the sheath and grain fill is compromised. The highest levels of damage are often found around field edges. Once larvae reach approximately 5.0 mm in length, normally 6-8 days, they fall to the ground and can burrow to a depth of 10 cm, before entering diapause.

Crops should be monitored to Mid-June.

Larvae and cocoons can survive in the soil for more than one year and it is known that couch grass and ryegrass are suitable alternative hosts.

Currently, there are no recommended insecticide treatments specifically for control of Saddle Gall Midge.

In an effort to better understand this pest, Dow AgroSciences are working closely with agronomists and farmers who have previously experienced losses caused by this pest. We hope to learn more of the best timing for control and, based on our extensive knowledge of controlling Orange Wheat Blossom Midge, the effects of Dursban* WG.

Dow AgroSciences invest in Pestwatch to help you provide the best advice to farmers. Baseline sampling has been taking place over the last week and we will communicate these results soon. 

How many doses of Dursban WG may I apply to a cereal crop?

The answer is three. Dursban WG is approved for use on winter or spring varieties of wheat, barley and oats. Two applications of up to 1kg/ha may be applied up to flag leaf (GS 39) and a further 0.6kg/ha up to before flowering (GS59).

Can I still sell Grazon 90? 

Yes. For Grazon* 90 (13117)  and other grassland products Thistlex (11533), Doxstar (11063) & Pastor (11168), as well as Timbrel * (5815) revocations have been rescinded and the existing approvals extended to 2021 - although this date will change once CRD are back on schedule with their review of associated Annex III packages. There are no restrictions on availability.

If you need some more Aminopyralid Farmer Certification forms please email E-mail: DowAgroSciencesUK@dow.com detailing your name and address and we will send you some.

Subscribing to Dow AgroSciences' Agronomy Update & Pestwatch gives eligibility for 1 Crop Protection BASIS Points annually. Please include course name "Agronomy Update & Pestwatch" and number "CP/16442/1011/G" on your training record. These details apply until 31st May 2011.

If you require any further information please contact our technical Hotline on 0800 689 8899 or your local Dow AgroSciences representative.

Use plant protection products safely.  Always read the label and product information before use.

*Doxstar, Dursban, Grazon, Pastor, Thistlex and Timbrel are trademarks of Dow AgroSciences LLC.
#Dow Shield is a trademark of The Dow Chemical Company.

All other brand names are trademarks of other manufacturers for which proprietary rights may exist.

Doxstar contains triclopyr and fluroxypyr
Dow Shield contains clopyralid
Dursban WG contains chlorpyrifos
Grazon 90 contains clopyralid and triclopyr
Pastor contains clopyralid, fluroxypyr and triclopyr
Thistlex contains clopyralid and triclopyr
Timbrel contains triclopyr

More info at www.dowagro.com/uk