Pests and diseases in combinable crops

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Introduction

Pests and diseases can affect crops and have a serious impact on the economic output of a farm. Farmers should vary their prevention and treatment methods depending on the crops they grow and the pests or diseases they are susceptible to, as they affect crops differently. Farmers also need to ensure that they balance pests and disease prevention and treatment methods against damage to the environment.

This guide covers how to control pests and diseases in different types of combinable crops. It will explain how to spot early signs of certain diseases, the symptoms that they show, and how to prevent certain diseases completely and reduce the effects of others.

Wheat disease management

Wheat disease management is essential for controlling diseases in the following areas of wheat:

foliar
stembase
root
ear

Seed production and certification

Certifying seed is one way to reduce pests and diseases, and all seed bought and sold in the UK must be certified. Wheat quality must meet EU minimum standards and member states can set their own, higher standards.

Farm Saved Seed (FSS) can be grown and processed on a farm. You must declare any use of FSS to the British Society of Plant Breeders (BSPB) and must not sell, share or exchange FSS. You can find out how to make an FSS declaration on the BSPB website.

Organic certified seed must meet the same standards as conventional seed.

Seed must be officially sampled and tested by the Food and Environment Research Agency (Fera) before certification. Find information on seed certification on the Fera website.

Seed-borne diseases

There are a number of seed-borne diseases, the most common of these being:

bunt
Microdochium seedling blight
Septoria seedling blight
Fusarium seedling blight
Ergot
seedling blight, foot rot and leaf spot
loose smut

To help recognise these diseases, you can find illustrated information on plant diseases on the Fera website.

Once you have confirmed the diseases you should then choose a product to treat it. You can download the Home Grown Cereals Authority’s (HGCA’s) wheat disease management guidance from the Agricultural Document Library (ADLib) website (PDF, 3.38MB).

Other diseases

There are a number of other diseases that can affect wheat crops and it is essential that you recognise these as soon as possible to limit contamination. Some of the most common diseases are:

foliar diseases - eg leaf blotch, leaf and glume blotch, yellow rust, tan spot, powdery mildew
root diseases - eg take-all
stem based diseases - eg eyespot
ear diseases - eg sooty moulds
virus diseases - eg barley yellow dwarf virus

Find illustrated information on plant diseases on the Fera website.

Assessing disease risks

You should start crop protection as upper leaves emerge, and before disease develops on yield-forming leaves. However, predicting disease is difficult and depends on a number of factors such as:

disease pressure
disease resistance rating
weather conditions

However, you can use crop management to limit disease risk. You can download the HGCA’s wheat disease management guidance from the ADLib website (PDF, 3.38MB).

Fungicides

Fungicides are often the best way to limit crop diseases. However resistance can occur when a disease becomes insensitive to a particular fungicide. To prevent resistance, you should:

practise good hygiene - eg disposal of crop debris
avoid large areas of any one variety of crop, especially in high disease areas
only use fungicides when treatment is necessary
use fungicides in mixture where possible to reduce the risk and use a minimum number of applications of the same active ingredient
regularly monitor crops for diseases and resistance

You can read updates on fungicide resistance on the Chemicals Regulation Directorate website.

Barley pest and disease control

Barley diseases can affect the growth and survival of both tillers and spikelets which can affect initial plant count. Therefore early disease management is vital, as initial plant count is important for a successful yield and economic profits.

Seed production and certification

Certifying seed is one way to reduce pests and diseases, and all seed bought and sold in the UK must be certified. Wheat quality must meet European Union (EU) minimum standards and member states can set their own higher standards.

FSS can be grown and processed on a farm. You must declare any use of FSS to the BSPB. You must not sell, share or barter FSS. You can make a FSS declaration on the BSPB website.

Organic certified seed must meet the same standards as conventional seed.

Seed must be officially sampled and tested by Fera before certification. You can find information on seed certification on the Fera website.

Seed-borne diseases

There are a number of seed-borne diseases, the most common of these being:

loose smut
leaf stripe
covered smut
seedling blights
seedling blight, foot rot and leaf spot
net blotch
Ramularia leaf spot
Rynchosporium

To help recognise these diseases, you can find illustrated information on plant diseases on the Fera website. Once you have confirmed the diseases you should then choose a product to treat it. You can download the HGCA’s wheat disease management guidance from the ADLib website (PDF, 3.38MB).

Foliar and stem-based disease control

Disease control should keep the crop healthy during the growth stages that are most important for yield. The three grain yield phases are:

number of ears per unit
grain numbers per ear
average grain weight

It is essential you keep crops protected from disease during these phases. These phases occur at different dates depending on winter or spring sowing.

The most common diseases to affect barley are:

foliar diseases - eg brown rust, yellow rust and powdery mildew
stem-based diseases - eg eyespot
ear diseases and mycotoxins - eg ergot
virus diseases - eg barley yellow dwarf virus, soil-borne mosaic viruses

Find illustrated information on plant diseases on the Fera website.

Assessment of disease risks

You should start crop protection as upper leaves emerge, before disease develops on yield-forming leaves. Forecasting disease is difficult and depends on a number of factors such as:

disease pressure
field resistance of the crop
crop variety’s genetic resistance

You can use crop management to limit disease risk. You can download the HGCA’s wheat disease management guidance from the ADLib website (PDF, 3.38MB).

Fungicides

Fungicides are often the best way to limit crop diseases. However resistance can occur when a disease becomes insensitive to a particular fungicide. To prevent this, you should:

practise good hygiene - eg disposal of crop debris
avoid large areas of any one variety of crop, especially in high disease areas
only use fungicides when treatment is necessary
use minimum amounts of fungicide
regularly monitor crops for diseases and resistance

Karnal bunt

Karnal bunt (Tilletia indica) is a quarantine fungus of wheat, durum wheat and triticale. It is not present in the EU but has been found in grain imported for consumption.

Effects of the disease

Karnal bunt reduces grain quality significantly which has an impact on grain marketability, and can cause large economic losses.

Countries where Karnal bunt is present often suffer damage to their export markets as countries often regulate against the disease. Therefore it is essential that this is not introduced to the UK.

Symptoms

The Karnal bunt fungus spreads through the infected seed from its germinal end along the seed groove. Occasionally however, the infection may be limited to the germinal end. The following symptoms may also be present:

dark coloured spores under the grain surface
badly infected grain can smell of rotting fish
grain splits at harvest leaving hollow or broken grains

The disease is currently found in the following areas:

Asia - India, Pakistan, Afghanistan, Nepal, Iraq and Iran
Mexico
USA
South Africa

Prevention

The disease is not currently present in any EU member state and prevention of spread is essential.

The disease spreads through the rupture of infected grains when they are harvested. The fungus then spreads to the soil where it can survive for up to five years - or longer if it is in stored seed - and contaminate further crops.

The only way to prevent the fungus is to acquire seed from an area or location where the fungus does not occur. You should follow this rule for:

wheat
rye
triticale
imported grain for feeding or milling

If you suspect you may have the presence of this disease, you should contact the Department for Environment, Food and Rural Affairs (Defra) Plant Seeds Health Inspector (PHSI) immediately. You can call the Fera PHSI Division on 01904 465 625 or email them at planthealth.info@fera.gsi.gov.uk. You can also find your nearest PHSI office on the Fera website.

Oilseed and other cereal disease and pest control

Controlling cereal diseases and pests varies slightly for each cereal crop, although the control methods are similar for all cereals.

Controlling oilseed and cereal diseases

Monitoring and using fungicides is the most efficient way to control cereal diseases. You can find a cereal disease encyclopaedia on the HGCA website.

Another way to control cereal disease levels is to monitor crop disease levels in your region. Crop Monitor is a HGCA-funded initiative that allows you to monitor crop health and crop protection in wheat and oilseed rape crops in England and Wales. Find information on crop pest and disease activity on the Crop Monitor website.

Fungicides

Fungicides are often the best way to limit crop diseases. However resistance can occur when a disease becomes insensitive to a particular fungicide. To prevent this, you should:

practise good hygiene - eg disposal of crop debris
avoid large areas of any one variety of crop, especially in high disease areas
only use fungicides when treatment is necessary
use minimum amounts of fungicide
regularly monitor crops for diseases and resistance

Oilseed and cereal pest control

The impact of pests on yield and quality can be more variable than that of many diseases. However, pest control must be balanced against damage to the environment and encouraging other insects which may benefit the crop.

The following steps can help you produce effective pest control:

assess the risk of infestations
minimise pest risk by cultural means
introduce natural enemies
use treatments where economically justified

You should follow general principles of pest management at each stage of the process.

Before sowing:

for pests that seed treatments may control - you should check whether they have caused previous crop damage, and if the risk has increased before using seed treatment
for pests that cultivations may control - you should check if regrowth increases pest risk before early ploughing or using dessicant

From sowing to emergence, you should check whether slugs pose a threat and whether they are above the threshold before sowing deeper, using traps or molluscicide.

After emergence, you should check if there is a risk of an imminent attack, and if natural enemies are present before treatment

For specific treatments of pests, you can find cereal pests factsheets on the Fera website.

For general information on rodent and pest control, see the guide on managing wildlife and pests.

Mycotoxins

Mycotoxins are toxic chemicals produced by specific fungi which infect crops. As different species produce mycotoxins of varying toxicity, there are different levels allowed into human and animal foodstuffs and feed.

Mycotoxins can be classified into two groups:

field mycotoxins
storage mycotoxins

Field mycotoxins

Mycotoxins can occur when a crop is out in the field. For example, Fusarium infection in grain ears can lead to mycotoxin development during flowering - especially when the weather is warm and wet. Field mycotoxins can also occur more often if harvests are delayed due to wet weather.

You can minimise field mycotoxins by limiting certain risk factors. In particular you should:

rotate crops to minimise wheat after maize, as maize can cause a high risk of potential mycotoxin pollution
remove straw to reduce crop debris or ensure crop debris is buried by ploughing
cultivate to mix crop debris into upper soil layer
consider ear spray during flowering, especially if weather is to be wet
apply the correct doses of fungicide during flowering, as close to infection time as possible
prepare crops before harvest to minimise delays
harvest grain as soon as possible
consider growing crops with lower risk of contamination

Download the HGCA’s guidance on reducing field mycotoxins from the ADLib website (PDF, 283KB).

Storage mycotoxins

Mycotoxins can also be produced when crops are in storage - particularly if grain exceeds 18 per cent moisture content. The greatest risks occur:

during harvest backlogs
during ambient air drying
when grain may take weeks to dry

To reduce the possibility of storage mycotoxins, check your grain is correctly dried and cooled. In particular, you should consider:

hot-air drying or stirring if you have wet grain - this reduces the length of time that grain is above 18 per cent moisture
cooling grain using an airflow rate of around 10 cubed metres per hour - you can measure the airflow rate yourself or get airflow data from a manufacturer
recording the length of time you run your fans
controlling fans using a differential thermostat
running bulk drying fans - if using - for a shorter time than cooling fans
ways of voiding hot air from any building containing fans

Spray technology

It is essential that if you are applying fungicide or pesticides to your crop that you use the appropriate sprays.

If you apply too much fungicide, insecticide or pesticides, then resistance may occur as disease can become insensitive to that particular spray. It is therefore essential that you apply the correct dose of the treatment to your crop. To do this, you must ensure that you calculate the correct volume of spray to use.

Low volume spraying

You should try to use the lowest volume of product you can. Although most products recommend application at 200 litres per hectare, they can often be sprayed at lower volumes and be just as effective.

If you use lower volumes, then coverage can be improved as you can cover a larger area of crops more efficiently.

When considering low volume spraying you should:

check manufacturer information to ensure that product can be applied at volumes lower than the minimum specified on the label
assess the extent to which using low application volumes can improve work rates
choose an appropriate nozzle for the target and to reduce drift risk
always check with your pesticide adviser before using water volumes below those recommended on the product label

You can use the HGCA spray volume calculator to work out how much of the relevant product you should use. Find the spray volume calculator on the HGCA website.

You will achieve maximum efficiency by:

maximising pesticide deposition on the correct area of the target plant - rather than achieving maximum deposition on the whole plant
ensuring that the distance between individual pesticide deposits does not result in variation in pesticide deposition between target plants
ensuring other factors, such as too low volumes and boom instability do not lead to variations in pesticide deposition between target plants
ensuring a high concentration of the pesticide in the spray solution does not impede its penetration of the plant

Spray nozzles

When applying sprays, you should also consider the nozzle you will use for applications. You can download HGCA’s spray nozzle selection information from the ADLib website (PDF, 249KB).

Organisations that can help

Controlling pests and diseases in combinable crops is an essential task and there are a number of bodies that can offer help and support.

Fera’s PHSI is responsible for import and export inspections of plants, plant products and certain other products such as soil, issuing phytosanitary certificates and scientific licences. You can call the Defra Plant Health Division on 01904 455 174 or contact your local PHSI. Download a list of PHSI offices from the Fera website (PDF, 25KB).

One of the major roles of the Defra is to help the farming industry operate as efficiently as possible. Defra administers European Commission support policies that provide around £3 billion to UK agriculture. They also oversee a number of agencies that work with arable farmers, imports and exports of crops, and implement pest and disease controls. You can call the Defra Helpline on 08459 33 55 77.

The Health & Safety Executive’s Chemicals Regulation Directorate (CRD), formerly Defra’s Pesticides Safety Directorate, is responsible for ensuring the safe use of pesticides or plant protection products - and their approval process - for agricultural, horticultural and home garden use.

Only approved pesticides can be sold, supplied, used, stored or advertised in the UK.

CRD is also responsible for biocides, industrial chemicals and detergents to protect the health of people and the environment.

For further information on pesticides, you can call the CRD Helpline on 01904 455 775.

You can read about CRD’s work and the approval process for pesticides on the CRD website or see the guide controls on chemicals in food.

The Organic Food Federation promotes organic methods and maintains high standards and best practice within the farming sector. For more information, you can call the Organic Food Federation on 01760 720 444.

In England, the Farm Advisory System [FAS] advises farmers about cross compliance. For further information, call the Cross Compliance Helpline on 0845 345 1302. Alternatively, for information on cross-compliance requirements, see the guide on cross compliance: the basics.

For more general enquiries, you can call the Defra Helpline on 08459 33 55 77.

The Rural Payments Agency (RPA) is responsible for licences and schemes for growers as well as for running the Single Payment Scheme (SPS). For more information about SPS and how it can help your farming business, you can call the RPA Helpline on 0845 603 7777.

The National Farmers’ Union (NFU) represents the farmers and growers of England and Wales. It aims to promote successful and socially responsible agriculture and horticulture, while ensuring the long term viability of rural communities.