Store pre-harvest hygiene - treat grain stores now 

Why should I control thistles in grassland? 

This edition's FAQs:

- Do I have to withhold grain after pre-harvest hygiene Reldan 22 treatment?

- Can Doxstar*, Forefront*, Pastor*, Thistlex* or Grazon* 90 be tank mixed with MCPA, 2,4-D or CMPP?

- Will Grazon 90 control Cow Parsley?

An important part of preparation for harvest is cleaning storage structures that will be used to hold grain. This includes general cleaning and maintenance and treatment with an effective store hygiene insecticide. Critically the treatment must also offer acaricidal control  for one of the commonest grain store pests - mites. The best product to use is Reldan* 22.

Mites, weevils and beetles are frequent problems in grain and grain stores and can be responsible for up to 10% of yield loss. To help insure against this, control measures should start up to one month before filling the store, through pre-harvest hygiene with the broad-spectrum insecticide and acaricide Reldan* 22.

Growers now have a much more limited choice of insecticides that they can use to treat grain stores. Some products cannot be used on all cereals, such as milling wheat, and others do not control mites, which are major and common pests in grain. Reldan 22 is fully registered for this use as well as on stored grain, and can be used in wheat, barley, oats, rye and triticale stores. Reldan 22 controls all major pests of stored grain, including mites, weevils, beetles and moths. It also is accepted by the British Beer and Pub Association (BBPA) and Brewing Research International (BRI) for use on cereals for malting and brewing.

Up to 10% of grain yield can be lost to pest and mite damage after harvest. These pests also damage grain directly, leading to poorer grain quality, including taint and extraneous insect fragments, as well as reducing nutritional value. Pest activity can also cause over-heating in the grain heap, leading to the development of moulds.

Stored grain is subject to a wide range of insect and mite infestations including common flour mite, cosmopolitan food mite, grain weevil, warehouse moth, saw-toothed grain beetle, red-rust flour beetle and merchant grain beetle, all of which are controlled by Reldan 22.

Empty grain stores need to be thoroughly cleaned and then treated with Reldan 22.  When the grain store is empty and up to one month before filling it again, it should be cleaned out of old grain, dust and debris which may be harbouring insects. Any grain handling equipment should also be cleaned.

Reldan 22 should then be applied to all structural surfaces of the empty store and handling machinery, taking care to treat all cracks, crevices and joints. There are several options for application: by knapsack sprayer with fan spray nozzles, by motorised knapsack sprayer or tractor-operated spray lance. Reldan 22 is applied at 200 ml in 5 litres of water per 100 square metres of surface.

With yield prospects depressed by the drought but with higher grain prices, it is well worth making sure all grain is protected from any damage in store, particularly if harvest turns out to be wet.

Summary

• Controls all major pests of stored grain including mites
• Works by contact, ingestion and fumigant action
• Fast knockdown and long-term control
• Use for pre-harvest hygiene of grain stores
  - There is no grain-withholding period for pre-harvest hygiene treatment
• Use on stored cereal grain

Learn more about Reldan 22

Download Reldan 22 Product leaflet

A 10% infestation of thistles in a sward, (i.e. 20 plants in a 35 m² area) will reduce grass production by 1.1 tonnes of dry matter per hectare.  At 40% infestation the loss rises to 4.4 tonnes of dry matter per hectare - an incredible waste of a valuable home-grown feed resource especially in a dry year where grazing and conserved forage will be short.

There are 20 species of thistle growing in the UK.  Of these the two most common and damaging in grassland are creeping and spear thistles.  Over one million hectares of grassland in this country are estimated to be infested with these pernicious weeds.

They most commonly occur in older swards, on soils with low levels of phosphate and nitrogen but high levels of potash.  Over and under grazing can encourage thistle colonisation.

As with all weeds, thistles compete strongly with grass for water, light and nutrients, and the grass in infested areas will not be grazed.  IGER research in the 1990's showed that cattle and sheep tend to leave 30 cm around each individual plant.  Their presence in hay and silage lowers feed quality and utilisation.

Creeping thistle is a perennial plant which grows from seed or root sections.  The seed can survive for up to 21 years in soil and is mainly spread by wind.  Mechanical topping reduces seed production, but not root spread.  Topping after the flowers have set will not stop seed maturing.

Roots of one plant can grow to cover up to 5 m² in one year, and up to 80 m² in two years.  The weight of the underground root system can be as much as two tonnes/ha.  These large underground systems allow thistles to withstand adverse conditions, such as drought, much better than grass.  To gain long term control of such large root systems requires treatment with a fully translocated herbicide.
The spear thistle is a biennial plant which grows from seed.  In the first year it can often go unnoticed, since it produces only a small rosette.  In the second year the plant can grow to over a metre in diameter before flowering.

Spear thistles are totally dependent on seeds for reproduction.  Unlike creeping thistles the plant does not have extensive lateral roots, but does have a very long tap root.

Each flower head produces 200-400 seed heads, and each seed head can product 4,000 to 8,000 seeds, which remain viable for more than three years.

Loss of grass production is not the only good reason for controlling thistles.  On sheep farms they are a danger to lambs, as their spikes can act like dirty hypodermic needles to animals that brush past them - breaking their skin and spreading diseases such as orf within the flock.  In this case, getting rid of thistles also cuts the cost and labour of inoculating lambs against infection.

There is an old saying about thistle control "Cut them in June, they come back soon;  Cut them in July, they will soon die."  Unfortunately this is one 'old wives tale' that is completely misleading.  In fact, controlling them when they have a flower head - with a topper or weed killer - is often the worst time to try.  If they are topped, seed will continue to mature on the ground.

Lasting control requires herbicide treatment when the thistles are young and actively growing with little stem.  This is known as the rosette stage, when there are four to ten leaves showing.
MCPA has been used in the past but many farmers have found the results disappointing.  This is because it only affects the biomass above ground, with little overall impact on the root systems below.  This means that typically the same fields will need repeat spraying year after year.

Thistlex*, from Dow AgroSciences, works differently.  Applied at 1 l/ha in 200 to 400 lt water, it offers a targeted, cost effective solution which actually tackles the problem underground. It is also very safe to grass and will not check growth.

Where thistles have started to produce a flowering stem, overall control will be diminished so if practical consider topping and spraying re-growth some 2 to 6 weeks later.

Where there is a 10% infestation of thistles, using Thistlex for just one season can reduce the population to a level where only knapsack applications of a suitable herbicide are needed to keep the sward completely clean the following year.

Do I have to withhold grain after pre-harvest hygiene Reldan 22 treatment?

No.  The need to withhold grain for 90 days only applies where Reldan 22 has been applied directly to the grain as an admixture.

Can Doxstar*, Forefront*, Pastor*, Thistlex* or Grazon* 90 be tank mixed with MCPA, 2,4-D or CMPP?

This approach is not recommended and is not supported by Dow AgroSciences. Quick 'burn down' of top growth with phenoxy-herbicides can hinder movement of the translocated active ingredients in Doxstar*, Forefront*, Pastor*, Thistlex* and Grazon* 90 to the roots, leading to poor levels of weed control.

Will Grazon* 90 control Cow Parsley?

Yes, at 4.0 l/ha before flowering (likely to be too late this year). Repeat applications may be needed.

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/19948/1112/g" on your training record. These details apply until 31st May 2012.

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, Forefront, Grazon, Pastor, Reldan and Timbrel are trademarks of Dow AgroSciences LLC.

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

Doxstar contains triclopyr and fluroxypyr
Forefront contains aminopyralid and fluroxypyr
Grazon 90 contains clopyralid and triclopyr
Pastor contains clopyralid, fluroxypyr and triclopyr
Reldan 22 contains chlorpyrifos-methyl
Thistlex contains clopyralid and triclopyr

More info at www.dowagro.com/uk