Potato Blight – Pre-Harvest Roundup – Grassland Weed Control

The recent unsettled weather and localised heavy showers are beginning to take their toll on all crops. Blight has been reported over the last week and spray intervals should be kept to no more than 7 days with the current high risk weather. Very few winter barley crops have been harvested but hopefully a more settled spell will allow the remaining acreage to be cut. Fusarium is very pronounced in both winter wheat and spring barley this season.When weather conditions are wet during flowering, high levels of ear blight can occur.


Where crops have reached the end of rapid haulm growth and canopy growth has begun to stabilize good protection may be achieved with fungicides such as Invader, Infinito, Ranman and Revus. OPTION which is straight cymoxinil may be tank mixed with any of these products to achieve better kickback. Curzate has good curative activity and may be tank mixed if the spray interval is stretched. Where crops are at full canopy growers must pay very close attention to ensure water volumes, spray pressure and nozzle selection are correct to maximize spray penetration of the haulms and reduce spray drift.


Winter wheat, spring barley and winter oats are all ripening quickly. These should be examined to decide whether or not they require pre-harvest treatment with ROUNDUP ENERGY for the control of annual and perennial weeds especially scutch, rough stalked meadow grass, thistles

etc.ROUNDUP should be applied when the grain moisture is below 30% which coincides with the hard dough development stage (GS.87). The safest time is 1-3 weeks prior to harvest leaving at least 7 days between spraying and harvesting. (DO NOT APPLY TO SEED CROPS).

Propionic Acid

As harvest begins the most widely used grain preservative, Propionic acid, will be in demand, especially if showery conditions continue. Propionic acid when applied to moist grain prevents moulds and bacterial activity. It also prevents deterioration, loss of dry matter, nutrition loss and removes the associated health hazard to grain handlers, livestock and the end user.

One tonne of Propionic acid on 100 tonnes of grain gives an additional energy value equivalent to 1.5 tonnes of barley. Therefore as well as preserving the grain it adds significantly to its energy value. The use of Propionic gives the grower greater flexibility at harvest, especially if the grain has a higher than desirable moisture content. If the weather is inclement at harvest Propionic acid offers a sense of security to the grower through its flexible application rates.


Weeds are directly competitive with grass and in many cases reduce the nutritional value of the sward. Annual weeds are most commonly a problem in getting a reseed established but thankfully few persist once the sward has been grazed or cut. The most common weed that this does not happen with is common chickweed. Chickweed will reduce dry matter and slows wilting. This causes loss of soluble nutrients in the field and as, effluent from silos. Docks are a perennial weed and have large leaves and substantial tap roots which they can readily regrow if defoliated. Docks thrive in high nitrogen conditions and along with chickweed need to be treated every year to ensure good control.

Where possible weed infested grass fields should be treated as soon as possible. Forefront, Doxstar and Pastor will give good control of docks but will not check the growth the grass.Use high water volumes to ensure good coverage i.e. 300-400lt/ha. Gorse should be sprayed now. Use Grazon 90 and ensure good plant coverage using a knapsack or hand lance on a tractor mounted sprayer. Bracken should be sprayed late July or August when it is in full frond. (When leaves are expanded). Use Asulox and again ensure good coverage via a knapsack and where a conventional tractor sprayer is being used to treat large areas, use high water volumes at least 400l/ha


Potato Blight Fungicide Selection – Trace Elements – Slug Control

The weather continues to be very unsettled. Growth has been good over the last number of weeks with most crops looking well, but spray days have been difficult to find and many crops have not been sprayed at the correct timing due to the absence of a suitable spray window. Blight is reported in many areas across the province. Rhynchosporium is present on almost all crops of spring barley. I would advise under current disease pressure to ensure spring barley crops get a robust T2 fungicide and winter wheat an earwash .SUMIALPHA should also be included at this time.


Alternating between different products with different modes of activity is an essential part of an anti-resistance strategy. As levels of blight inoculum build over the course of the season, so growers must guard against the possibility of the fungus becoming resistant to the chemistry used – overuse of any one product will increase the likelihood of this dramatically. Continue therefore to switch between products from different chemical classes that are active on zoospores, so providing the best protection against tuber blight.
Product Types and Mobility in the Plant

There are three different ways by which the blight fungicide moves through the plant:
Contact fungicides eg. DITHANE, RANMAN, SHIRLAN, TIZCA – these products protect only the outer surface of the leaf onto which they are deposited. They do not move into the leaf and therefore do not normally protect any new growth that emerges after application.
Translaminar fungicides eg. CURZATE M WG, HARPOON, INVADER, RESPLEND, REVUS – these products move into the leaf onto which they are sprayed and then redistribute throughout the leaf tissue as it increases in size. They become rain-fast once they are in the leaf.
Systemic fungicides eg. CONSENTO, FUBOL GOLD, INFINITO – these products move in through the leaf surface and upwards into the new growth that emerges between applications, protecting that new growth from infection also.
Last year BASF brought to market a new active ingredient from a novel fungicide group, ametoctradin. This active has excellent activity against foliar and tuber blight and is rainfast in less than 1 hour. It moves into the leaf and is redistributed to the growing margins, so protecting the leaf as it grows in size. It also binds strongly to the waxy layer on the surface of the leaf and is redistributed over the surface onto new forming leaves. This makes the product ideal for use during the rapid canopy phase. To manage resistance, the active is co-formulated with more than a full rate of dimethomorph (relative to INVADER) and marketed as RESPLEND. The dimethomorph brings excellent curative activity to the product also and makes the product well suited right through the stable canopy phase.

Product Selection and Growth Stage

Early canopy development phase, emergence to rosette – Products that have zoospore activity are the most effective 1st spray, applied at the rosette stage prior to rapid haulm growth. RANMAN, SHIRLAN or TIZCA will control any zoospores that may be in the soil (either from ground-keepers or infected seed) and provide good protection of the new plant. Rapid canopy development phase, end rosette to beginning tuber initiation – Because of the considerable amount of new growth being produced during this phase, it is essential the product being used is fully systemic to properly being put on between applications. Later planted crops are higher risk as they produce more new growth between applications than earlier planted crops, at a time when the level of inoculum in the air is progressively increasing. Of the fully systemic fungicides, only those based on propamocarb effectively control all genotypes including the A2-13 strain. With the withdrawal some years ago of MERLIN & TATTOO, CONSENTO is the only fully systemic in the marketplace, containing propamocarb and fenamidone. The fenamidone adds a different mode of activity and builds in early tuber blight activity also.

Late canopy development, tuber initiation phase -As the crop canopy closes across the drills, the crop starts to initiate tubers. From this point on these daughter tubers are vulnerable to infection, so fungicide selection must also consider introducing tuber blight control, spread by zoospores being washed off any infected leaves or stems. At this stage INFINITO should now be introduced. Being fully systemic and translaminar it continues to protect new growth, and being curative it provides kickback should any foliar/stem blight appear. INFINITO remains one of the highest rated of the 21 products compared by the Euroblight group last year.

Canopy stable, tuber bulking phase -The need for systemic activity diminishes as the rate of haulm growth slows down during the mid season tuber bulking phase. Tuber blight activity should also become a factor as tuber development gets underway.Having tuber blight activity INFINITO is an ideal choice at this time also, but because it is limited to a maximum of 4 applications, 1 or 2 applications should be kept back to apply when severe pressure comes on, mid or late season.Other excellent alternatives at this time are INVADER & RESPLEND. The dimethomorph component of both products is curative and very persistent within the leaf and stem, so both are ideal alternatives when pressure is high. Both are translaminar, protecting the foliage as it fills out. The maximum dose for dimethomorph has been increased from 150gm/ha to 180gm/ha, both products now putting this higher rate on at each application. This has further improved the kickback and persistence of both products.
If the spray interval becomes unavoidably stretched by a day or two beyond 7 days, HARPOON should be tank-mixed at full rate along with whatever product is being used to provide the kickback effect this product gives. HARPOON is cymoxanil and is the most curative active available, meaning it will control any latent infection that may already entered the leaf as a result of the delayed application. However it breaks down within 3-4days after application, hence it must only be applied in mixture with another fungicide when curative activity needs to be maximised.

Improving Rainfastness

If spraying during periods of unsettled weather, rainfastness of all products will be further improved with the addition of a sticker to the spray solution. GUARD is a latex sticker and will improve the retention of the fungicide onto leaf surface, so improving both adhesion onto the leaf immediately post application, and over the following days should rainfall levels remain high.

General Comments on Good Practice

Never use any blight product at reduced rates; to do so will seriously compromise its performance, reduce its persistence, and encourage the selection of blight resistance.
As most products are either contact or translaminar only, coverage of the maximum surface area of the plant is critical. Maintain water volumes of at least 200lt/ha from the start to ensure good coverage, increasing to 300lt/ha in very leafy crops later in the season.
Make sure nozzle type used is correct to ensure sprayer pressure, droplet size and water volume applied are as per the label; these factors are as important product choice in terms of achieving good coverage of the foliage. Inspect and calibrate nozzles regularly to maintain performance. Trials have shown that fitting angled nozzles alternating to face forwards & backwards along the boom gives better coverage of the plant and significantly reduces drift.

Maintain boom height at correct height above the canopy throughout the season to ensure correct spray pattern and minimise drift; 50cm for 110° fan nozzles spaced 50cm apart.
Do not spray when leaves are wet as this will significantly increase the likelihood of runoff, so reducing the amount of active retained on or into the leaf .Make sure points and areas around line poles are fully covered. Inspect crops regularly throughout the growing season to identify any outbreak early, and determine growth stage. Use this to assist with product selection.

Trace element deficiencies

During the main canopy development phase the rate of new growth is extremely rapid. This places a huge uptake demand on the uptake of all nutrients, and in conditions of such rapid growth any nutrient that is limited in availability will suppress haulm growth, and as tuber initiation begins, tell the plant to form fewer tubers also. Manganese, sulphur and magnesium are three of the potentially most limiting trace elements, and timely application of these nutrients in an immediately available foliar formulation will offset this yield limiting effect.So that the crop is not adversely affected, it is essential to apply 2-3 maintenance applications of Mn, S & Mg along with N before symptoms are seen, the first going on at the onset of tuber initiation, which normally coincides with about 30-50% ground cover.


The damp spring has been ideal for slugs, so there is an increased risk of slug damage this season on crops in heavier ground. The damper soil encourages slugs to come up to the soil surface, so providing the ideal opportunity for good control. The key timing for effective slug control is just before the crop canopy meets across the rows. Miss this timing and the control will be less effective regardless of how many times they are treated. Take advantage of any rainfall by applying pellets just after rain when the slugs move up onto the soil surface, Potato varieties particularly susceptible to slug damage include Maris Piper, Desiree and Kerrs Pinks


Chlorpyrifos – Say No To Drift

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T3 Fungicides – Potato Blight – Grassland Weed Control

After another mixed bag this week conditions remain ideal for many diseases. Blight pressure remains high with the first outbreak of the season confirmed by AFBI earlier this week.Where potato crops are at the main canopy development it is essential the product being used is fully systemic to properly protect the new leaves being put on between applications. Later planted crops are higher risk as they produce more new growth between applications than earlier planted crops, at a time when the level of inoculum in the air is progressively increasing.
During the main canopy development phase the rate of new growth is extremely rapid. This places a huge uptake demand on the uptake of all nutrients, and in conditions of such rapid growth any nutrient that is limited in availability will suppress haulm growth, and as tuber initiation begins, tell the plant to form fewer tubers also. Manganese, sulphur and magnesium are three of the potentially most limiting trace elements, and timely application of these nutrients in an immediately available foliar formulation will offset this yield limiting effect. So that the crop is not adversely affected, it is essential to apply 2-3 maintenance applications of Mn,S & Mg along with N before symptoms are seen, the first going on at the onset of tuber initiation, which normally coincides with about 30-50% ground cover.
Aphid’s damage potato plants directly through feeding damage and indirectly by transmission of several viral diseases, of particular importance in seed crops – aphid control is necessary on seed crops to prevent the spread of potato leaf-roll, mild and severe mosaic viruses. Aphids are the vectors for these viruses i.e. it is the aphids by their feeding action which pass the virus on from one plant to the next.
A number of different species of aphids are responsible for viral spread. When checking plants for aphids, look at both sides of leaves at all levels of the canopy, and monitor the whole crop, not just the headlands. The crop is most vulnerable to virus transmission at the early growth stages, so it is vital to control once aphids are seen – the early sprays are much more important than later treatments in limiting virus spread.
BISCAYA controls all important aphids, including MACE resistant species, by both its contact and systemic modes of action. Central to its efficacy is its penetrant which greatly improves retention on the leaf. The oil forms a film after the water has evaporated, enhancing penetration of the active ingredient, thiacloprid, into the leaf, thereby speeding and prolonging activity. BISCAYA provides the same degree of efficacy in the mid-canopy leaves of the potato plant as on the upper leaves, still providing over 90% control 14 days after application. As a resistance management strategy its label allows only one application in ware crops and two in seed. In order to minimise the possibility of resistance developing, other aphicides with different modes of activity should be included. BISCAYA should be used first in the control programme to take out any aphids resistant to other approved aphicides.

Spring Barley

Ramularia (also known as leaf spot) is widespread in spring barley with the newer barley varieties showing more sensitivity to this late developing disease. It shows itself late on in the season (usually after booting), symptoms are very similar to manganese deficiency appearing as brown necrotic speckling on the upper leaves. Symptoms appear where crops are subjected to stress from alternating periods of wet weather & sunshine, or man-made as a result of scorching. Chlorothalonil (BRAVO) is very effective when used preventatively, helping to maintain green leaf area when used along with a triazole/strob mixture.

T3 Wheat

With ripening still approx 6 weeks away, the T3 treatment has to persist for all of this duration to prevent infection from a range of diseases such as SeptoriaNodorum (glume blotch), as well as Tritici, late season ear moulds and Fusarium. The cornerstone for the head spray fungicide is a strong triazole, giving strong curative activity to control any disease already on the plant as well as good persistence to prevent re-infection right up to ripening. Prothioconazole & epoxiconazole remain the most effective products to give ongoing Septoria protection as well as controlling fusariums and microdochiums on the ear. Prothioconazole (PROSARO) is the highest rated triazole for this range of diseases. The addition of a strobilurin is also essential to extend the persistence of the triazole and improve activity on Yellow Rust. Good grain fill is totally dependent on retaining green leaf area for as long as possible, and the addition of the strobilurin extends the retention of green leaf tissue.

Aphids in cereals

Aphids are now appearing in crops and as the grains begin to fill they feed at its base, drawing off the sugars that should be filling the grain if left unchecked.
Growers need to continue checking crops for aphid’s right up to milky ripe stage (GS73), and spray if present in numbers.


Grassland herbicides use growth function to kill weeds, therefore peak growth periods should be used for herbicide application. There must be sufficient growth to allow herbicides to be effective and vegetive growth is the key time to apply, as the chemical then gets drawn down into the roots. Herbicides are less successful once plants have progressed to the reproductive stage and have thrown a stem or began to seed. Once weeds are beyond the ideal growth stage for spraying they should be mown or topped and allowed to regrow again, and a herbicide applied to the fresh young growth.
To optimise efficacy of any herbicide, recommended water volumes should be observed, even when it means more time spent spraying. It is important to note ragwort plants in their second year are now coming close to flower and should be sprayed immediately as flowering ragwort is poorly controlled. The routine herbicide treatments for this weed are full rate MCPA or 2, 4-D, and they are most active on growing rosettes with reduced activity as the stem starts to extend. They are not clover safe. You can use a mixture of both these products as Nufarm Lupo which allows an increased dose herbicide compared with either alone, with a consequent activity benefit. Stock must be kept of until the weeds have rotted away, which can take up to six weeks.

Grain Store Hygiene

Ensuring stores are clean and pest free is essential to prevent any problems after all the hard work of growing and harvesting the crop. Now is the time to make grain stores ready for the coming harvest. Pest problems in stored grain arise from within the store itself, so a good clean-out is essential to minimise the carry-over of grain beetles, weevils and mites. The store should be empty and thoroughly cleaned before any treatment is carried out, removing all traces of grain and dust that might harbor insects or mites. Apply using an applicator to spray all surfaces including underside of roof and floor, concentrating especially on areas where dust can collect – cracks, light fittings, around equipment etc. RELDAN can be applied up to one month before filling the store and has no with- holding period when applied to the fabric of the store.


Carrot willow aphid is now flying into crops and they carry several virus diseases that affect both carrots and parsnips. They may cause leaf distortion and stunting if they infest plants at the seedling stage. Crops should be checked for aphids and an aphicide such as APHOX used if present. Where couch grass is a problem in carrots ARAMO can be used and has annual meadow grass as a label weed.


Metaldehyde – Get Pellet Wise

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T2 on Winter Cereals – Dock Control in Grassland

All weed control should now be almost complete on spring cereal crops. There was certainly plenty of opportunity to catch up on spray programmes over the last couple of weeks. Crops are moving through the growth stages very quickly this week with the damper conditions. Some spring barley in parts of North Down are already at flag leaf and East Down have crops with awns appearing. Wild oats may be controlled now as long as a period of three weeks has occurred from the weed spray application. Axial and Adigor may be used on both spring barley and spring wheat up to flag leaf. It is certainly a season where growth regulator will be required in abundance. As most crops are now past 2nd node growth regulation products are limited to Cerone for barley up to first awns visible and Adjust and Cerone on to spring wheat up until flag leaf sheath opening. Fungicide application is priority now as rynchosporium is spread by rain splash. This disease has been present in low levels up until now with netblotch being the most dominant disease in spring barley. Whatever the fungicide choice for spring wheat it is critical to include something to cover mildew as most varieties have mildew present on them.

Winter Cereals

Protecting the top three leaves at T2 is critical to yield and profit – up to 80% of the yield is generated from these leaves. Foliar disease not controlled effectively at this time will hasten the senescence of these leaves during grain filling, and therefore affecting yield and grain quality. Yet there is little point in applying any input if it does not give a financial return. To get the best return on fungicides, applying them at the correct timing is critical. Trial work in UK & ROI has consistently shown even in a low disease pressure year, a well-timed application will give returns of 2-4 times their cost and in high pressure situations 5-6 times their cost. In winter barley this should be applied from the end of booting through to awns fully emerged, GS45-59, and be robust enough to protect the upper leaves and ear through to the end of the season. Awns also contribute to yield and it is important to keep them free of disease also.
For winter wheat the T2 should ideally be applied between mid flag leaf to mid-booting, GS38-45 along with the growth regulator. The T3 treatment is then applied post ear emergence to mid flowering, GS59-65, targeting ear diseases and prolonging control of foliar disease on the top two leaves, especially important in wetter seasons and on susceptible varieties.Sumi-alpha should be applied along with the fungicide.


Much of the potato crop this season has gone into cold soils and therefore drills are only warming up now. Both weeds and potatoes have been slow to emerge to date. Most weed control programmes are based on residual products ie products that are taken up through the soil, and are therefore very dependent on sufficient soil moisture to work effectively. Soil conditions are ideal therefore at the moment, moist enough on the tops of the drills to allow the herbicide be taken into the soil and taken up by the germinating weeds.
A huge amount of SAC work suggests that growers should spray before crop emergence to moist clod-free ridges. Holding off until crop emergence will set the potatoes back significantly reducing final canopy cover, and compromise weed control especially if weather delays the application further. The weeds are best treated pre or very early post emergent, especially important on the difficult weeds; fumitory, knotgrass, bindweed, annual meadow grass.
The key message is to apply the herbicide combination before crop emergence, therefore avoiding any check to the crop once emerged and maximising range of weeds controlled.
It is Tuesday today as I write this article and the steam is rising up from the road as I look outside. This certainly has been the first day since potato planting I could say there is a risk of blight. During the early canopy development phase, emergence to rosette products that have zoospore activity are the most effective 1st spray. RANMAN, SHIRLAN or TIZCA will control any zoospores that may be in the soil (either from ground-keepers or infected seed) and provide good protection of the new plant.


With farms being short of grazing because of the cold conditions 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 helping to stimulate weed growth. To optimize results, wait for 2-3 weeks after cutting for docks to regrow to the rosette stage, and then apply DOXSTAR to actively growing plants. Doxstar has been developed to deliver the highest levels of dock control. The formulation and the presence of two actives; fluroxypyr and triclopyr, delivers a significantly higher level of control than straight fluroxypyr.

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. 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.

FOREFRONT may be applied onto grazing ground giving excellent weed control with no effect on the grass. FOREFRONT contains Fluroxypyr and aminopyralid. As well as controlling docks it will control chickweed, buttercup, dandelion, nettle and thistle.
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.

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