Maize Web Worm Pest Management: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

The Maize Webworm, Cryptoblabes gnidiella, belonging to the Family Pyraustidae of the Order Lepidoptera, also known as the Southern Corn Webworm. It is a polyphagous moth whose larvae feed on the maize plant’s leaves, stems, and ears. The damage caused by the larvae can significantly reduce crop yield and quality. The larvae can also carry fungal and bacterial diseases, affecting the crop’s yield and quality.

The pest can potentially spread diseases, such as the maize streak virus. To effectively manage this pest, it is important to understand its life cycle, its preferred habitats, and the best methods for controlling it. This article will provide an overview and discussion of the Maize Web Worm Pest in Maize crops, including its symptoms, identification techniques, and control.

Maize Web Worm Pest Management

Life Cycle of Maize Web Worm Pest in Maize Crop

Egg: The female worm lays up to 100 eggs. The eggs are laid on the upper and lower surfaces of the leaves of maize plants.
Larva: The eggs hatch within five days, and the larvae feed on the underside of the maize leaves.
Pupa: After about five weeks of feeding, the larvae spin a web and form a pupa. It remains in this form for 1-2 weeks.
Adult: After 1-2 weeks, the pupa emerges as an adult. The adult moths feed on the pollen and nectar of maize flowers.

The Maize Webworm is a very active pest with a high reproductive rate. It can complete up to 6 generations in a single season, with each generation lasting about 25 days. The larvae are particularly active at night and can cause extensive damage in a very short period.

Occurrence of Maize Web Worm Pest in Maize Crop

Location of maize web worm pest: This pest is native to Central and South America and is found to infest the maize crops in Africa, Brazil, Argentina, Colombia, Peru, India, Bangladesh, and China.
Host range: The maize webworm pest can infect different crops, including maize, wheat, sorghum, millet, and rice.

Factors Favoring the Population Increase of Maize Web Worm Pest in Maize Crop

Climate – High temperatures, high relative humidity, and abundant rainfall provide ideal conditions for this pest’s rapid development and reproduction.
Food availability – Maize webworm has a wide range of food sources, which helps increase its population. These include weeds, other grasses, and other crop plants.
Natural enemies – Predators such as birds, reptiles, and other insects can help control the maize webworm population.
Crop residues – Crop residue left in the field provides an ideal breeding ground for the maize webworm. The presence of crop residue also provides an ideal food source for the pest to feed on.

Identification of Maize Web Worm Pest in Maize Crop

Egg: The eggs are small, white, and oval-shaped, laid in solitary on the grains and spikelets.
Larva: The larvae are yellowish-green in color, have a black head, and are 1.2cm long.
Pupa: The pupae are brownish-gray and are about 5-6 cm long.
Adult: The adult worm is a dull-gray moth with dark grey forewings and a wingspan of up to 1.75 cm.

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Damage Symptoms of Maize Web Worm Pest in Maize Crop

The first sign of an infestation is usually a webbing of silk in the whorls of the corn plant.
The larval stage of the maize webworm is the damaging stage, feeding on the maize plant’s leaves, tassels, and ears.
The larvae feed on the lemma of the flowers, disrupting the chlorophyll and then on the young milky grains.
The damage is most severe when the larvae are present during pollination. The larvae feed on the flowers and kernels, resulting in small ears with few or no kernels.
The caterpillars create webs on maize cobs that block photosynthesis, reducing the plant’s ability to produce food and energy.

Percentage of Yield Loss in Maize Due to Maize Web Worm Pest

In the United States, yield losses can be between 40-60 percent in some states. In some areas, losses can exceed 60 percent.
In Mexico, losses can range from 10-20 percent. In Brazil, yield losses range from 10-50 percent.
In Colombia, losses range from 10-20 percent, while in Argentina, losses are between 10-30 percent.
In Peru, losses are estimated to be between 20-40 percent. In Africa, yield losses range from 10-60 percent in some countries.
In India, the yield losses are between 40-50 percent in some areas. In Bangladesh, losses due to the maize webworm are estimated to be 10-30 percent. The ETL is 40-50 larvae per plant.

Cultural Control of Maize Web Worm Pest in Maize Crop

Sanitation – Remove all dead or dying plants and other debris from the field. This helps to reduce the number of overwintering sites for the pest.
Timely planting – Planting maize at the right time helps to reduce the risk of infestation by maize webworms, as the larvae are most active during the late summer months. Planting maize at the right time also helps to ensure that the crop matures before the larvae become active and can cause significant damage.
Traps – Traps can also be used to reduce the population of the maize webworm. The pheromone traps attract the adult moths and capture them before they can lay eggs on the crop.

Biological Control of Maize Web Worm Pest in Maize Crop

Parasites – Parasites are natural enemies of webworms that feed on the larvae and pupae of the pest. The Trichogramma spp., Microplitis spp., and Eucelatoria spp. can be applied to the field using an inoculum of eggs, pupae, or adult moths.
Pathogens – The pathogens such as the entomopathogenic fungus Beauveria bassiana and Metarhizium anisopliae infect the larvae and pupae of the pest and cause their death.
Predators – Predators such as lady beetles, lacewings, and ground beetles feed on the larvae and pupae of the pest.

Chemical Control of Maize Web Worm Pest in Maize Crop

Spray Monocrotophos 35 SL or Endosulfan 35 EC of 1L per hectare.
Other insecticides, including organophosphates, pyrethroids, and carbamates, are usually applied as foliar sprays or soil treatments. Their mode of action is by disrupting the nervous system of the pest.
Organophosphates act quickly and are effective against a wide range of pests. So, they can be toxic to beneficial insects and should be used cautiously.
Pyrethroids are synthetic compounds that act as contact insecticides. They are highly toxic to beneficial insects and should be used with caution.
Carbamates are applied as foliar sprays. They are less toxic to beneficial insects and have a long residual effect.

Preventive Measures for Control of Maize Web Worm Pest in Maize Crop

Ploughing and cultivating the soil after harvesting helps expose the pupae to the sun and desiccation, thus killing them.
Timely weeding, crop sanitation, and proper irrigation can be practiced to reduce the risk of infestation of maize webworms.

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Conclusion

The maize webworm is a major pest of maize crops. It can cause extensive crop damage, resulting in farmers’ poor yields and financial losses. Monitoring the crops regularly and practicing preventive measures to reduce the incidence of pest is necessary. Integrated pest management strategies, including resistant varieties, cultural practices, and chemical controls, can effectively control the spread of this pest and protect crops.

Maize Web Worm Pest Management: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

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