Armyworms are insect pests that can cause significant damage to crops, including eggplants. These caterpillars, the larvae of several moth species, feed on a variety of plants, including sugarbeet, alfalfa, beans, eggplants, and tomatoes, as well as several types of weeds.
In the winter and spring, armyworm populations tend to be concentrated on weeds, but as the weather warms up and host crops begin to grow, moths lay their eggs on the young leaves of these plants. Once the eggs hatch, the larvae feed together near the egg cluster before dispersing as they grow.
Armyworms Management in Eggplant
The Life Cycle of Armyworms
- The life cycle of armyworms begins when they overwinter as pupae in the soil. Adult moths emerge from the soil from March to July and mate before laying eggs on host crops. Depending on environmental conditions, the eggs hatch into small larvae that feed on the host plant for 5 to 8 weeks.
- As the larvae mature, they gradually disperse from their original egg cluster and continue feeding on the host plant, causing significant damage. Once they have finished feeding, the mature larvae enter the pupal stage in the soil, where they will remain until they emerge as adult moths in the following spring.
- There are typically two generations of armyworms yearly, with the second generation hatching in late summer or early fall. These larvae feed until early October before entering the pupal stage to overwinter in the soil.
Identification of Armyworms in Eggplant Field
- Armyworm moths are grey and brown in adult form, with a 1.25 to 1.5 inches wingspan. Depending on the species, they may also have grey or tan-colored patterns. On their wings, they feature a recognizable “V-shaped marking.
- Egg: Beet armyworm eggs are ridged, pale green to pink, and in a mass wrapped in a substance that resembles grey cotton. Often, they are arranged in groups on the undersides of leaves.
- Armyworm larvae are 1.25 to 1.5 inches long and come in various colors, including olive green, light green, and yellow, as well as grey with dark patterns and yellow with dark grey or black markings. Their skulls have a characteristic inverted “Y” shape.
- Pupa: Armyworm pupae are about 0.75 inches long and reddish-brown. They are usually found in the soil or leaf litter at the base of host plants.
Damage Symptoms of Armyworms in Eggplant Fields
- Defoliation: Armyworms can quickly defoliate eggplant plants, stripping them of their leaves and reducing their ability to produce energy through photosynthesis.
- Fruit loss: As the fruit forms, armyworms may feed on the calyx, causing damage and scarring to small fruit. This can result in reduced yield and lower-quality products.
- Plant stunting: Severe armyworm infestations can cause eggplant plants to stunt, reducing their growth and overall productivity.
- Visible feeding damage: Armyworm larvae can leave visible feeding damage on the leaves and fruit of eggplants, including ragged holes and missing tissue.
- Fecal matter: Armyworms leave behind fecal matter as they feed, which can accumulate on the leaves and fruit of eggplants, making them unattractive and unsellable
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Armyworms Management in Eggplant by Cultural Method
- Thorough tillage: Armyworms and cutworms often overwinter in plant debris and weeds, so thorough tillage can help to reduce their overwintering and feeding sites. Tilling the soil in the fall can also help to destroy or expose overwintering pupae.
- Weed control: Weedy fields and field borders provide food sources for armyworms, so controlling weeds can help to reduce their populations. Removing cool-season weeds along field edges can also starve young caterpillars. Lambsquarters and wild mustards are attractive plants for egg-laying, so removing them can reduce the likelihood of egg-laying.
- Crop rotation: Armyworms are attracted to certain crops, so rotating eggplant with crops that are less attractive to armyworms can help to reduce their populations.
- Sanitation: Removing and disposing of infested plant debris and material can help reduce armyworm populations and prevent the spread of infestations to other areas.
Armyworms Management in Eggplant by Biological Method
- Parasitoids: Parasitoids are insects that lay eggs in the bodies of armyworms, and their larvae develop and feed on the host, eventually killing it. The wasps Hyposoter exiguae and Chelonus insularis are common parasitoids of armyworms.
- Predators: Predators are organisms that feed on armyworms. Some common predators of armyworms include ground beetles, spiders, and birds.
Armyworms Management in Eggplant by Chemical Method
- Insecticides: Insecticides containing active ingredients such as spinosad, bifenthrin, cyfluthrin, and cypermethrin can control armyworms in eggplant fields. These insecticides can be applied as foliar sprays or as soil treatments. It is important to read the insecticide label carefully before use to ensure proper application rates and to avoid harm to non-target organisms.
- Systemic insecticides: Systemic insecticides such as imidacloprid can also control armyworms. These insecticides are applied to the soil or as a foliar spray, and they are taken up by the plant roots or foliage and transported throughout the plant. When armyworms feed on the plant, they ingest the insecticide and die.
Armyworms Management in Eggplant by Organic/Natural Method
Horticultural oils, such as neem oil, suffocate the larvae by coating their breathing pores. They are effective against different larvae stages and help prevent fungal growth in the plant. Complete plant coverage, including undersides of leaves and junctions with stems, is critical for effective control.
Preventive Measures for Control of Armyworms
- Clean Farming Practices: Practice clean farming by removing and destroying crop residues and weeds that are overwintering and feeding sites for armyworms.
- Early Detection: Use pheromone traps to detect the presence of adult moths and monitor for signs of infestation in the crop.
- Natural Predators: Encourage the presence of natural predators such as birds, wasps, and flies that prey on armyworms.
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Conclusion
There are several management strategies available to control these pests. Farmers can use cultural, biological, chemical, and organic/natural methods to prevent and control armyworm infestations. It’s essential to use these methods and implement preventive measures such as regular monitoring, pheromone traps, and planting to attract birds and beneficial insects to achieve the best results. By following these practices, farmers can reduce the impact of armyworms on eggplant crops and ensure a successful harvest.
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