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.

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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.


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.


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

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



Risk factors

How to minimise the risk

Control options


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


Larvae feed on growing seedlings

Previously undisturbed grassland


South-facing fields 

Insecticide seed dressing


Allow a substantial break between grassland and maize



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



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 or call 0247 799 0069.

Learn more about integrated pest management (IPM)