When dealing with stem borers, it’s important to recognize the damage caused by pests like Scirpophaga incertulas and Chilo incertulas, two species that belong to the Crambidae family, better known as snout moths. These insects are often hard to spot, especially when distinguishing between males and females, as their physical differences are subtle. Males are generally smaller and lighter in hue, whereas females tend to be larger and more richly colored.
Stem Borer Control
Scientific name: Scirpophaga incertulas
However, the true impact comes from their larvae, which burrow into the plant stems, weakening them and causing wilting or yellowing, particularly in rice plants. These larvae can go unnoticed for a while, but their damage is significant, often making it seem like the plant is suffering from a disease rather than pest infestation. As these species mature, they continue the cycle of destruction, exiting the plants to pupate and start the process all over again. Early identification and intervention are key to preventing a larger infestation and protecting the crops from irreversible damage.
| Topic | Details |
|---|---|
| Species | Scirpophaga incertulas, Chilo incertulas (both belong to the Crambidae family, also known as snout moths) |
| Identification | Distinction between males and females: Males are smaller with lighter markings, while females are larger and darker. |
| Damage | Larvae burrow into plant stems, weakening the plant and causing wilting or yellowing, particularly in rice fields. |
| Lifecycle | Males and females lay eggs on plant stems. The larvae emerge, tunnel into the plant, leave to pupate, and then begin the process anew. |
| Control | Early identification and pest management are crucial to minimize damage to crops and prevent larger infestations. |
Distribution
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Scirpophaga incertulas and Chilo incertulas are widely distributed across various regions.
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Found in Asia, where they cause significant damage to rice crops.
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Present in Africa, affecting agricultural productivity.
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Recorded in Europe, especially in countries like Spain.
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Oceania also faces challenges, with Australia and Papua New Guinea experiencing infestations.
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Notable presence in Egypt, where stem borer pests damage rice fields.
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These pests adapt well to different climates, making them resilient in diverse environments.
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Effective management requires understanding their global distribution and localized impact.
Hosts
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Stem borer pests like Scirpophaga incertulas and Chilo incertulas primarily target rice crops.
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These pests infest both cultivated rice plants and wild species of rice.
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Larvae of these pests burrow into the stems, causing significant damage to the plant.
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While rice is the main host, other cultivated plants and wild species can sometimes be affected.
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The damage is most severe in rice fields, making it a critical crop to monitor for infestation.
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The ability to infest a range of hosts makes it challenging to control stem borer populations effectively.
Symptom of Damage
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Egg mass is typically found near the leaf tip at the vegetative stage.
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Larva hatches and burrows into the stem, targeting the growing shoot.
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Drying of the central shoot occurs, leading to a dead heart in the plant.
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Grown up plants show dried ear heads and chaffy grains.
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The appearance of a white ear indicates severe damage, with empty or damaged ears.
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Brown coloured patches along the stem show signs of complete infestation.
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Significant yield loss occurs, with reduced crop quality and value.
Nature of Damage
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In the vegetative phase, the larvae burrow into the stem.
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The central shoot becomes damaged, often causing the plant to die off and turn yellow.
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This leads to the formation of a dead heart, where the inner tissue is destroyed.
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At the ear-bearing stage, the ear head may appear dry or light-colored, indicating damage from feeding.
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The white ear head results from severe damage, with no healthy grains.
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In extreme cases, the plant may be pulled up from the base, further weakening it.
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These damages significantly reduce the plant’s ability to produce a healthy crop.
Identification of Pest
| Life Stage | Description |
|---|---|
| Eggs | Pale white, flattened, oval-shaped eggs are laid in clusters near the leaf tips, surrounded by buff-colored hairs. |
| Egg Period | Lasts 5-8 days before hatching into larvae. |
| Larvae | Initially pale yellow with a dark brown head and prothoracic shield, feeding inside the rice stem. |
| Larval Period | Lasts 28 to 30 days, causing damage to the plant. |
| Pupation | Forms a white silken cocoon in straw or stubble for pupation. |
| Pupal Period | The period lasts for 8 to 10 days before the adult moths make their appearance. |
| Female Moth | Bright yellowish brown, black spot on forewings, tuft of yellow hairs near the anal region. |
| Male Moth | Smaller, pale yellow forewings, no black spot on the forewings. |
Favourable Conditions
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Stem borer pests thrive in fields that are planted with rice.
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Infestation increases when surrounding fields are susceptible or when stubbles from previous crops remain.
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Stubbles provide a breeding ground for stem borers, leading to higher pest populations.
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ETL (Economic Threshold Level) exceeding 10% of plants showing Deadheart symptoms indicates critical infestation.
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Deadheart symptoms in 2% of plants are a clear sign of damage.
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The presence of White ear symptoms further signals severe crop loss due to stem borer damage.
Management Strategies :
Cultural Methods
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Fields should be regularly scouted for vulnerable crops at various growth stages.
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Early detection of dead hearts and white ear symptoms is crucial for timely intervention.
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Removal of affected plants and proper disposal prevents further spread of pests.
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After harvest, manage stubbles as they provide breeding grounds for borer populations.
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Plant resistant varieties such as Ratna, TKM 6, IR 20, IR 40, and IR 56 to reduce infestation.
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Close planting of seedlings and transplanting techniques can help eliminate pest hiding spaces.
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Regularly removing and destroying egg clusters can help reduce the number of pests.
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Continuous water stagnation can disrupt pest development and further infestations.
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Ploughing at ground level after harvest helps disturb the pest’s habitat.
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These methods also help prepare the field for the next crop while controlling stem borer populations.
Chemical Methods
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Chemical methods are crucial when ETL exceeds 10% or when dead heart and white ear symptoms are observed.
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Egg masses found at a density of 2/m2 during the vegetative stage require immediate chemical application.
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Newly hatched borer larvae should be targeted to prevent further damage.
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During the flowering stage, if 2% of plants show white ear symptoms, chemical control is necessary.
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Common chemicals include:
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Quinalphos 25 EC and Phosphamidon 40 SL, applied at 1000 ml/ha.
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Profenophos 50 EC at 600 ml/ha.
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Spraying should occur at 7-day intervals to ensure effectiveness.
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Proper timing is crucial; delayed application may reduce efficacy.
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Consider using natural enemies of stem borers to reduce chemical dependency.
Biological Methods
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Release of egg parasitoids like Trichogramma japonicum to target egg masses laid by stem borers.
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Egg parasitoids are introduced three times at weekly intervals, beginning 28 days post-transplantation (35 DAT).
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Total release of 1 lakh egg parasitoids per ha for effective control.
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Continue release of parasitoids until 42 DAT.
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Application of Bacillus thuringiensis var kurstaki at 2.5 kg/ha targets larvae and reduces pest population.
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Place egg cards with parasitoids on the leaf surface during the morning hours.
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Avoid chemicals for three days or seven days after field release of biological agents to protect their effectiveness.
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This approach provides a natural substitute for chemical pesticide applications.
Natural enemies and predators:
Natural Enemies
| Natural Enemy | Type | Action |
|---|---|---|
| Tetrastichus schoenobii | Wasp | Parasitizes stem borer larvae, reducing pest populations. |
| Telomomous rowani | Wasp | Parasitizes stem borer larvae, helping control pest numbers. |
| Stenobracon nicevillei | Wasp | Parasitizes and controls stem borer larvae. |
| Cotesia flavipes | Wasp | Targets stem borer larvae, helping to reduce pest damage. |
| Agriocnema pygmae | Damselfly | Preys on stem borer larvae, contributing to pest control. |
Predators
| Predator | Type | Action |
|---|---|---|
| Lycosa pseudoannulata | Spider predator | Hunts and preys on stem borer larvae and adults. |
| Metioche vittaticollis | Cricket | Feeds on stem borer eggs and larvae, helping control pest populations. |
Trap Methods
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Light traps can cover up to 5 ha and are designed to attract and kill adult moths.
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Placing bird perches near traps can encourage bird predators to feed on captured moths.
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Sex pheromone traps use specific pheromones to lure male stem borer moths.
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Pheromone traps should be set at a density of 10 to 12/ha for effective monitoring.
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Traps help in monitoring stem borer populations and provide data for timely control measures.
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Check and replace traps at 15-20 days intervals to maintain effectiveness.
In conclusion, effective management of stem borer infestations relies on a combination of cultural, chemical, biological, and trap methods to control and reduce pest populations. Cultural methods, such as early detection, proper field management, and the use of resistant varieties, help minimize damage, while chemical methods provide a quick solution when pest levels exceed threshold limits. Biological control, through the release of natural predators like wasps and damselflies, and the use of natural enemies, offers a sustainable and eco-friendly approach. Trap methods, including light traps and sex pheromone traps, are valuable tools for monitoring pest populations and providing timely control measures. By integrating these strategies and remaining vigilant in monitoring, farmers can effectively protect their crops from the damaging effects of stem borer infestations.
FAQS
What is a stem borer?
When dealing with stem borers, such as Chilo polychrysus, it’s essential to understand the impact these boring insects have. They are a serious pest, often targeting rice, maize, sugarcane, and wheat. The larvae of these borers inflict considerable harm by burrowing into plant stems, disrupting crop growth. These pests infest various plants, wreaking havoc on agriculture by boring into the stems, which is a critical concern for farmers.
How do you get rid of stem borers?
A comprehensive strategy is crucial for controlling stem borers effectively. Start by focusing on cultural practices and physical removal of infested stems. If that doesn’t work, as a last resort, chemical control can be applied. Insecticides such as Bt or pyrethroids can be sprayed, following the correct label instructions carefully. Utilizing row covers can also help minimize the impact while maintaining the health of your crops.
What are the symptoms of stem borers?
In a nutshell, the symptoms of stem borers include dead hearts or tillers caused by their boring activities. Small holes may appear on the stems and tillers, accompanied by frass or fecal matter within the damaged stems. Additionally, oval patches of eggs can be found near the tip of the leaf blade, signaling the presence of these harmful pests.
What is the chemical control of stem borers?
Effective chemical control of stem borers requires targeting the freshly emerged larvae. This can be done by applying quinalphos or phosphomidon in two rounds, each at 1000ml/ha, spaced out by a 7-day interval. Based on the ETLs, you can opt to spray Any of the following options can be used: Quinalphos 25 EC, Phosphamidon 40 SL, or Profenophos 50 EC. Always follow the appropriate label instructions for safe and effective use.
How to control stem borer naturally?
To control stem borers naturally, it’s essential to implement regular monitoring of pest populations and employ crop rotation. Integrating biological control with agents like parasitoids and predators can significantly reduce the numbers of these pests. Additionally, using neem alongside other organic methods not only enhances the effectiveness of pest control but also ensures long-term management of stem borers in an eco-friendly manner.