Maize has the highest potential among all cereals. Almost 197 million Hacter land is covered by maize crops globally. The USA is a large producer of maize and Pakistan also vital contribution to maize production
Improper management of diseases can play a significant role in yield and can cause nutritional famine for food industries. Improper and late harvesting is another reason for the reduction in yield. We should explore effective strategies to manage and diminish their impact. Develop tools for identifying different diseases at the farmer level. We should try to make farmers familiar with diseases for their easy management. Incorrect recognition of diseases can lead to harmful effects on the maize crop and this way management becomes more difficult.
Global demand for maize products is rising day by day so our farmers need to remain fully informed about the increasing trend of diseases. For this purpose, farmers should be able to use different managing tools, new varieties, and sustainable management practices. Pest management is also essential for diminishing of the impact of diseases on the maize crops. This will be a successful contribution to globally rising food security and agricultural sustainability
The Diseases of Maize and its Management
1. Leaf blight of maize
Leaf blight of maize, also known as maize leaf blight or simply corn leaf blight, is a plant disease caused by various fungal pathogens that affect the leaves of maize (corn) plants. This disease can lead to significant reductions in yield and overall plant health if left unmanaged. Several types of leaf blight can affect maize, each caused by different fungal species.
Two common types of maize leaf blight are:
a. Northern Corn Leaf Blight (NCLB):
- Causal Agent: The fungal pathogen Xestobium turcica (formerly known as Helminthophobia turcica) is responsible for causing northern corn leaf blight.
- Symptoms: NCLB typically appears as long, elliptical lesions that are grey-green to tan in colour, often with a dark border around the edges. These lesions can cover a significant portion of the leaf surface and reduce the plant’s photosynthetic capacity.
- Impact: Severely infected plants may experience reduced photosynthesis, decreased grain filling, and ultimately lower yields. The disease is more prevalent in cooler, wet conditions.
b. Southern Corn Leaf Blight (SCLB):
- Causal Agent: The fungal pathogen Ophiobolins heterotrophs (formerly known as Bipolarism maydis) is responsible for causing southern corn leaf blight.
- Symptoms: SCLB symptoms appear as oblong lesions with tan centres and dark brown borders. These lesions can also cause leaf tissue death and reduced photosynthetic efficiency.
- Impact: Similar to NCLB, SCLB can lead to yield losses due to reduced photosynthesis and overall plant health. It is more prevalent in warmer and humid conditions.
2. Downy mildew of maize
Downy mildew of maize, also known as maize downy mildew or Bipolarism spp., is a plant disease caused by various species of the Bipolarism genus. It primarily affects maize plants and can lead to significant yield losses if not managed properly.
Symptoms of Downy Mildew in Maize:
Initial symptoms usually appear on the leaves as small, pale green to yellowish spots. As the infection increases, the spots may become enlarged and develop a characteristic “downy” appearance. Infected leaves may curl and twist, and the growth of the maize plant can be stunted.
In many cases, the entire plant can be affected which can lead to reduced kernel development and poor production.
3. Leaf spots in maize
Leaf spots in maize (corn) are a common maize disease that can be caused by various pathogens, including fungi, bacteria, and sometimes viruses. These leaf spots can affect crop health and yield if not managed properly. Here are some key points about leaf spots in maize:
Causes: Leaf spots can be caused by different pathogens, with fungal species being the most common culprits. Some common fungal pathogens that cause leaf spots in maize include Cercosporin zeal-maydis, Bipolarism spp., and Colletotrichum Gramin cola. Bacterial pathogens like the Xanthomonas species can also cause leaf spot symptoms in maize.
Symptoms: The symptoms of leaf spots in maize can vary based on the causal pathogen, but they generally include the appearance of small to large lesions on the leaves. These spots may be circular or irregularly shaped. The centers of the spots may become necrotic and the affected areas may merge as the disease chance increases.
Strategies for Maize Disease management:
Disease management in maize crops is crucial to ensure healthy plant growth and maximize yields. Maize, also known as corn, can be affected by various diseases caused by fungi, bacteria, viruses, and other pathogens. Here are some effective disease management strategies for maize crops:
- Choose maize varieties that are resistant or tolerant to common diseases in your area. Planting resistant varieties can greatly reduce the risk of disease outbreaks.
- Sanitation: Refinements and sanitation are essential for maize fields. Proper disposal of crop residues can prevent pathogens from attacking.
- Resistant Varieties: Farmers should be well informed about the use of resistant varieties. Resistant varieties save the crop from different pathogens and diseases and can cause an increase in yield.
- Timely Planting: Disease attacks can also be decreased or minimized by planting at the right time. Managing plants at the right time can lower disease pressure.
- Seed Treatment: Treating maize seeds with fungicides or biological agents before planting can protect emerging seedlings from soil-borne pathogens and seed-transmitted diseases.
- Hygiene and Sanitation: Maintain clean field conditions by removing crop residues and weeds, which can harbour disease-causing organisms. This prevents the buildup of inoculum that can cause future infections.
- Proper Plant Spacing: Avoid planting maize too densely, as crowded plants can create conditions conducive to the spread of diseases by reducing air circulation and increasing humidity.
- Fertilization and Nutrient Management: Balanced nutrition can help plants build stronger defences against diseases. Avoid excessive use of nitrogen, as it can promote certain diseases.
Pests of Maize and their Management
Maize crops can be affected by various pests that can cause damage to the plants and reduce yields. Here are some common pests that can impact maize crops:
1. Corn Earworm (Helicoverpa zeal):
This is a major pest that can cause damage to the ears by feeding on the silk and kernels. Larvae of the corn earworm can bore into the tips of developing ears, leading to contamination and reduced yield.
2. Fall Armyworm (Spodoptera fruited):
Fall armyworm larvae feed on maize leaves, causing defoliation and reducing photosynthesis. Severe infestations can result in significant yield losses.
3. Stalk Borer (Papa Pema debris):
Stalk borers can tunnel into the stem of young maize plants, weakening the plant and causing lodging (falling over). This can lead to reduced yield and difficulty in mechanical harvesting.
4. Maize Weevil (Sitophilus zamias):
Maize weevils are stored grain pests that can infest stored maize, causing damage and reducing grain quality. They lay eggs inside kernels, and the larvae feed on the grain.
5. Aphids:
Aphids can infest maize plants, sucking sap from the leaves and transmitting viruses. Their feeding can lead to stunted growth and reduced yields.
6. Wireworms:
Wireworms are soil-dwelling pests that feed on seedlings, causing irregular stands and poor emergence. They can damage maize roots and affect plant growth.
7. Cutworms:
Cutworms are nocturnal caterpillars that cut through young maize seedlings at or just below the soil surface. They can lead to standing reductions and uneven plant growth.
8. Leafhoppers:
Leafhoppers are sap-feeding insects that can transmit diseases to maize plants, affecting their overall health and yield potential.
9. Whiteflies:
Whiteflies can infest maize plants and secrete honeydew, which can promote the growth of sooty mould. They can also transmit viruses to plants.
10. Spider Mites:
Spider mites are tiny arachnids that feed on plant sap, causing stippling and discolouration of leaves. Severe infestations can lead to reduced photosynthesis and plant stress.
11. Rootworms:
Rootworm larvae feed on maize roots, affecting nutrient uptake and plant stability. Severe infestations can result in lodging and reduced yields.
How to manage pests in maize?
To manage these pests effectively, consider the following strategies:
- Implement integrated pest management (IPM) practices, which involve monitoring pest populations, using cultural control methods, and resorting to chemical control only when necessary.
- Use resistant maize varieties when available.
- Rotate maize crops with non-host crops to break pest cycles.
- Practice proper sanitation, such as removing crop residues and weeds that can harbour pests.
- Employ biological control agents like predators and parasitoids to naturally regulate pest populations.
- Use targeted chemical treatments, such as insecticides, when pest populations exceed economic thresholds.
Weeds Management in Maize
Weeds can act as hosts for disease-causing organisms. Keeping weed populations under control can reduce disease incidence. Weed management in maize (corn) is crucial to ensure optimal crop growth and yield. Weeds compete with maize for nutrients, water, and sunlight, reducing crop productivity.
Here are some strategies for effective weed management in maize:
1. Crop Rotation:
Rotate maize with other crops that have different weed spectrums. This can disrupt the life cycles of weed species that are specific to maize and reduce their populations over time.
2. Tillage Practices:
Proper tillage can help control weeds by burying weed seeds and disrupting their growth. However, excessive tillage can also lead to soil erosion and degradation. Reduced tillage or no-till practices can be beneficial, but they require the use of other weed control methods.
3. Mulching:
Mulching with organic materials like straw or crop residues can suppress weed growth by blocking sunlight and providing a physical barrier. It also helps conserve soil moisture.
4. Cover Crops:
Planting cover crops between maize rows can help decrease weed growth by outcompeting them for resources. Cover crops also improve soil health and fertility.
5. Herbicides:
Herbicides are chemical compounds designed to control weeds. Selective herbicides target specific weed species without harming the maize crop. Non-selective herbicides can be used before planting or in non-crop areas.
6. Mechanical Weed Control:
This includes using tools like cultivators, rotary hoes, and flame weeders to physically remove or damage weeds. Mechanical methods are effective but require careful timing to avoid damaging the maize crop.
Ali Haider, Noor Fatima, Muhammad Usama Abdul Qayyum, Mazhar Hussain, Shahid Ali, Muhammad Kamran, Aoun Abbas, Muhammad Abdullah
University of Agriculture Faisalabad, Pakistan
