Corn pests and diseases: Complete guide with photos

Hello to all agrohuerters! Last week we saw how to grow corn in the organic garden. In today’s article, we will take the magnifying glass of entomologists to find out what are the pests and diseases of corn and how we can control them.

1. Corn pests and diseases: Most important pests

Corn can be affected by various types of pests. To facilitate their study they are usually divided into 4 categories:

1. Pests that develop in the aerial part of the plant.
2. The ones that live in the ground.
3. Pests that live inside the plant.
4. Lastly, the rodents and birds that feed on the crop and then leave.

The aerial parts of the plant are attacked by some insects that we have already talked a lot about in other articles. These insects are aphids, spider mites and caterpillars. Therefore, I am going to leave you the different links to each article:

aphids on corn

You can find information on how to get rid of aphids in the post » 11 solutions to combat aphids in the garden « and other links to that article.

Red spider corn leaves

« Fight the red spider in the organic garden «

Caterpillars in the corn crop

« I have caterpillars on my plants, how can I eliminate them? «

wire worms

We can identify them by other names such as «pins» or «doradillas» and correspond to the larval stage of different species of beetles. Mainly: A. obscurus, A. sputador and A. lineatus.

They spend the winter half buried and reappear around the month of April. The small larvae feed on young roots, which is why the main damage occurs in the early stages of the crop. They can also attack the buried part of the neck, causing serious injuries to the plant.

corn donuts

They are also known as gray worms and belong to the Noctuidae family, within the Lepidoptera order .They are caterpillars that feed mainly on the neck of plants. Throughout the day they hide and at night is when they feed. They usually lay on weeds or spontaneous plants around them.

For its control it is recommended:

• Place pheromone traps.
• Know their migratory times.
• Eliminate weeds.
• Monitor the early stages of crop development, as this is the time when they are most susceptible.

corn with white worms

White worms are known as the larval stage of many coleopterous insects of the Scarab family, whose most famous representative is the “sanjuanero beetle”. The damage is caused by its larval stage, which lasts two years. Later they will become beetles. These beetles bury themselves to lay their eggs. They can also affect small rootlets.

nematodes in corn

Nematodes are a species of worms that live in water and soil. They are usually transmitted by irrigation water, contaminated substrates, or by tools that have previously been in contact with affected areas. The larvae enter the plants through the parts that are in contact with the soil (absorbent root hairs).

They parasitize the roots of plants, preventing the normal absorption of water and nutrients.This results in a decrease in growth, wilting and yellowing of the leaves.The clearest symptom is nodules on the roots.

For more information about this plague and how to prevent and eliminate it, you can consult the post Nematodes: what they are and what to do if they cause diseases.

corn drill

It could be said that the corn borer is one of the most important pests in this crop. These caterpillars damage the ears and stalks of corn as they tunnel into them to feed.

Main means of control:

• Light traps or pheromone traps.
• Crop rotation.
• Chopped or buried stubble.

Birds and mammals that attack corn

Corn is not exempt from being gnawed or bitten by some mammals and birds. Among them, those that usually cause the most damage are:

• BIRDS: crows, sparrows, magpies, rooks,…
• MAMMALS: voles, field mice,…

To control this type of pest, deterrence techniques such as firecrackers are usually used. Firecrackers are usually effective but the birds are able to memorize the frequency of the explosions and, then, they will stop being so. Scarecrows, protective mesh or rodent traps are also often used.

2. Maize diseases

corn rust

Fungal disease characterized by causing brown pustules on corn leaves. It usually appears in bands and is located in the middle part of the leaf. It develops in places with high humidity.

Anthracnose corn leaves

Anthracinosis is a fungal disease that causes rotting of stems and leaves.

Some prevention methods:

• Good soil drainage.
• Crop rotation.
• Clean crops of weeds.
• Red thyme application.

References

• Nalam, V., Louis, J., & Shah, J. (2018).Plant defense against aphids, the pest extraordinaire. Plant Science, (April), 1–12.
• Fathipur, Y., Maleknia, B. (2016). Chapter 11 – Mite Predators. Publisher(s): Omkar. Ecofriendly Pest Management for Food Security. Academic Press. 329-366.
• Abrol, D., Shankar, U. (2016). Chapter 20 – Integrated Pest Management. Editor(s): Surinder Kumar Gupta. Breeding Oilseed Crops for Sustainable Production,
  Academic Press. 523-549
• Simon, JC, & Peccoud, J. (2018).Rapid evolution of aphid pests in agricultural environments. Current Opinion in Insect Science, 26, 17–24.

This is all for today, I hope that now you know a little more about corn pests and diseases, and see you in the next article.

Have a nice day!