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For the latest guidance on oilseed rape crops this autumn, read the Corteva OSR update by clicking here. Topics covered include:

• Oilseed rape crop status and growth
• Weed control and herbicides use
• Starting to think about propyzamide for blackgrass or ryegrass control?
• Have you downloaded the Corteva Arable App to access Kerb Weather Data?
• Field observations and Corteva hotline key questions answered
• Give extra support to your oilseed rape crop by stabilising nitrogen in the Autumn
• Get the most out of our updates and be in with a chance of winning our monthly prize draw

The good spring continues, with little excuse for all fieldwork not being up to date. Ground conditions continue to be excellent, with silage being cut in ideal conditions, maize drilling and potato planting is now completed in most areas. Unfortunately for many waiting on the rain last weekend it amounted to very little and spring cereal crops are beginning to show signs of stress.

Potatoes

Where broad –leaved weed control has yet to be completed and the crop has passed the latest timing for Sencorex a reduced rate of Sencorex tank-mixed with Titus will provide a wider weed spectrum of weed control than Titus used alone and can be used on emerged crops up to 25cm high where the label allows. Scutch, other grasses or volunteer cereals are not controlled by the Titus/Sencorex mix. Where these weeds become a problem in coming weeks the graminicide Falcon can be used. Falcon can cause transient yellowing and is therefore not approved for use on seed crops. The first fungicide application should be made at the rosette stage or sooner if a blight warning has been issued. Potato farmers should be aware products containing metribuzin i.e Sencorex must be used up by 24^th November 2025.

Grassland

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 must be sprayed before flowering as flowering ragwort is poorly controlled. The routine herbicide treatments for this weed are Thrust, Lupo 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. Forefront is also very effective on ragwort. Stock must be kept off until the weeds have rotted away, which can take up to six weeks.

Buttercups are now ready for treatment. Best results are achieved if sprayed before flowering. ENVY is very effective on both buttercup and dandelions. Envy contains florasulam and fluroxypyr. Together they deliver excellent control of weeds found in pastures which typically get over grazed, receive minimal nitrogen or have poorly competing grass species present. Envy has no manure management restriction and has a short seven-day stock withdrawal period so animals can return quickly. Envy is very safe to grass and won’t hold back its growth. Buttercups are best controlled when they are still green and leafy and before the main flowering period. Envy will still give reasonable control even when the weed is flowering but for the best effect treat now. Product choice depends very much on which other weeds are being targeted.

Spring Cereals

The extended period of dry weather has allowed farmers to make significant progress on field work. For many growers it has been the earliest end to a spring planting season in a number of years.

Weed control has been difficult to date as crops are growing well but weeds are only just germinating due to the very dry conditions. To minimise the effects of competition on the crop and optimise the level of weed control, herbicide application should be carried out once all weeds have emerged but are still small, and before they begin to compete with the crop for nutrients and light. Carrying out the weed control when they are at the 2-4 leaf stage is much more effective especially on difficult weeds such as fumitory and knotgrass. Whilst chickweed resistant to a wide range of herbicides is commonplace right across the province, the  inclusion of the active arylex into the herbicide tank-mix programmes in recent years has given improved control of  chickweed and other problem weeds including fumitory and sets a new benchmark in terms of weed control in spring barley and wheat. It belongs to a chemical family classified as synthetic auxins, similar to the old hormone chemistry and controls a wide range of broad-leaved weeds including those resistant to the ALS herbicides in most winter and spring cereals, including robust control of fumitory, fat-hen and ALS resistant chickweed. Marketed as ZYPAR, it is available in co-formulation with the active ingredient florasulam and has excellent multiway compatibility along with a very wide range of other pesticides and has no major following crop restrictions. It gives excellent control of a wide range of broad-leaved weeds that includes chickweed, fumitory, fat-hen, groundsel, brassica weeds, and cleavers, but its weakest weed is redshank. Whilst it will control it alone up to 6-leaf, when tank-mixed with ALLY MAX/RACING TF it will control redshank right up to flowering.

Temporary nutrient issues

Manganese (Mn) deficiency is widespread in much of our local soil types, and particularly damaging to leaf vigour and yield if not treated. Continuous cereal cropping, ground recently limed and dry soils all increase the likelihood of deficiency.  Symptoms begin with small pale green speckles appearing throughout the leaf and these will progress to turn brown unless treated. Barley is particularly susceptible to Mn deficiency. MAXMAN is a highly concentrated Mn(40%) in a completely soluble chelated nitrate formulation and also supplies 10.8% Nitrogen and 11.4% Sulphur

A young plant that is growing extremely rapidly is producing a huge amount of new plant tissue each day. This rapid growth is limited only by the availability of nutrients to synthesise biomass, dependant on soil fertility and the plant’s own root development to take up the nutrients. It is at this time therefore when nutrient deficiencies are most likely to appear and in doing so, suppress growth rates.

The application of a broad-spectrum trace-element mix along with key macronutrients during this time is a very useful and beneficial way to supplement the plant’s nutrient requirements during periods when availability does not meet demand, most likely to coincide with phases of rapid growth ie. during tillering and as stem extension begins. Application of a balanced and readily available source of macro & micronutrients that is topping up what is being made available from the  soil at this key time will minimise the adverse effects of restricting nutrient availability. CEREAL HIGH N-supplies 250gm N, 125gm S, 38gm Mg, 93gm Mn, 45gm Cu and 15gm Zn per ha

FASTMIX MAGNESIUM PLUS is an alternative product specifically formulated to meet the increased micronutrient demand of cereals and other combinable crops with good yield potential. It is a quick acting foliar fertiliser containing high levels of magnesium and sulphur as well as manganese, zinc and boron, all in a water soluble form and readily available to the plant. It is very compatible in tank-mix with most pesticides and can be applied along with the T1 and T2 fungicide applications. Being a dry formulation, it should be fully dissolved in the tank first and other products added afterwards.

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