Pest, weed and disease threats to maize

Weed control in the first six weeks after sowing is critical to maize performance, and the most potentially damaging pest and disease to maize are wireworm and maize eyespot. Seek advice from a BASIS-qualified agronomist as to the most appropriate treatment for any crop pest or disease.

Weed control in maize

Maize seedlings struggle to compete with other plants, such as weeds or volunteers from previous crops. Weed control during the first six weeks after sowing is crucial to killing weeds before they impact crop performance. Competition with weeds for nutrients and moisture is most damaging during the first six weeks post-emergence. Herbicides and inter-row hoeing are the main forms of weed control.

Pre-emergence

Residual herbicides are sprayed onto the drilled seedbed to remove any weeds that germinate alongside the maize. This approach gives the maize a head start.

Post-emergence

Most fields require a second, early post-emergence herbicide spray when the crop has one to three leaves. This tackles the second flush of weeds. Delaying this post-emergence application will reduce the final crop yield.

The benefits of spraying early

A Maize Growers Association (MGA) weed control trial showed that spraying weeds early (within two weeks of crop emergence) resulted in low levels of competition and yields similar to all-season weed control (Figure 2). Leaving weed control to six weeks post-emergence resulted in significant crop yield reductions.

Product choice should be based on the weeds present and those expected to germinate over the coming weeks. Seek advice from a BASIS-qualified adviser and follow best-practice application to protect watercourses and the wider environment. The Voluntary Initiative offers further guidance.

Figure 1. Maize Growers Association trial of weed control timing

Bar chart to show MGA trial of weed control timing

Pesticide regulations

From 2014, farmers have had to demonstrate their use of Integrated Pest Management (IPM) with regard to chemical applications. From 26 November 2015, all sprayer operators were required to have the relevant certification to apply pesticides (including those previously exempt due to grandfather rights). From 26 November 2016, all working application equipment must have a National Sprayer Testing Scheme certificate.

Pest threats to maize

Pest	Damage	Risk factors	How to minimise the risk	Control options
Birds	Crows, in particular, like to feed on maize seeds	Shallow sowing depth	Bury seeds well	Treat seed with bird repellent Employ traditional bird scaring techniques
Wireworm	Larvae feed on growing seedlings	Previously undisturbed grassland South-facing fields	Insecticide seed dressing Allow a substantial break between grassland and maize Ploughing	Seed dressing or cultural, e.g., crop rotation
Frit fly	Second generation maggots eat the young seedlings in May and June	Predominantly grassland areas	Leave a ten-week gap between grass and drilling maize	Seed dressing or cultural, e.g. crop rotation

Bird damage to a maize crop

Image copyright Bayer CropScience Limited.

Wireworm damage to a maize crop

Image copyright Bayer CropScience Limited.

Frit fly damage to a maize crop

Image copyright Bayer CropScience Limited.

Disease threats to maize

Disease	Damage	Risk factors	How to minimise the risk	Control options
Maize eyespot Kabatiella zeae	First seen as spotting on the leaf. When the spots are held up to the light, a yellow halo can be seen around each one	Wet, cool conditions Non-inversion cultivation techniques, e.g. min-till Proximity to fields with maize crop residues Two or more years of maize cultivation	Plough maize stubble Drill late into a warm seedbed Rotate the maize crop with other crops	Fungicide treatment as soon as the disease is identified, plus second treatment if conditions remain wet/cold Disease stops at temperatures above 27°C
Fusarium mould	Mould populations can build in maize and pose a real threat to the following winter cereal	Repeated maize cropping Previous wheat cropping Exposure to crop residues and stubble	Grow maize in rotation with grass Do not rotate with wheat Remove or bury crop residues	No fungicides available

Disease

Damage

Risk factors

How to minimise the risk

Control options

Maize eyespot

Kabatiella zeae

First seen as spotting on the leaf. When the spots are held up to the light, a yellow halo can be seen around each one

Wet, cool conditions

Non-inversion cultivation techniques, e.g. min-till

Proximity to fields with maize crop residues

Two or more years of maize cultivation

Plough maize stubble

Drill late into a warm seedbed

Rotate the maize crop with other crops

Fungicide treatment as soon as the disease is identified, plus second treatment if conditions remain wet/cold

Disease stops at temperatures above 27°C

Fusarium mould

Mould populations can build in maize and pose a real threat to the following winter cereal

Repeated maize cropping

Previous wheat cropping

Exposure to crop residues and stubble

Grow maize in rotation with grass

Do not rotate with wheat

Remove or bury crop residues

No fungicides available

Useful links

Download our guide to growing and feeding maize silage

To order a hard copy of the Growing and feeding maize for better returns manual, please contact publications@ahdb.org.uk or call 0247 799 0069.

Learn more about integrated pest management (IPM)

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