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How to Prevent Leaf Rollers

Introduction

Sâu cuốn lá nhỏ, also known as the small leaf roller, is one of the most harmful pests, especially in rice plants. Farmers are concerned about the small leaf roller and are unsure of the appropriate preventive measures. AgriSearch, or Agri.vn, is here to share with you how to prevent the small leaf roller. Don’t miss out on this article!

Scientific Name

Cnaphalocrosis medinalis

Family

Pyralidae

Order

Lepidoptera

Harmful Symptoms

The leaves of rice plants are rolled by the small leaf roller. The larvae feed on the upper epidermis and chlorophyll of the leaves along the veins, creating long white streaks. These streaks can connect to each other, reducing the photosynthetic area. In particular, when the leaves are young or functional leaves are affected, it significantly reduces the yield.

Recognizable symptoms of the small leaf roller
Recognizable symptoms of the small leaf roller

Morphological Characteristics

– Male: The front edge of the forewing is brownish yellow, with two diagonal brown-black streaks from the upper edge of the wing to 2/3 of the wing.

– Eggs: Oval-shaped with a very fine network of veins. They are laid on the upper and lower surfaces of leaves. Newly laid eggs are slightly translucent, and when close to hatching, they turn ivory yellow.

– Larvae: The newly hatched larvae are white in color, with a brownish-black head. As they grow, the body changes from greenish to yellowish, with a light brown head.

– Pupae: They are yellowish-brown and are usually found inside rolled leaves.

Newly hatched small leaf roller larvae are agile and flexible
Newly hatched small leaf roller larvae are agile and flexible

The small leaf roller larvae are agile and flexible, crawling on the leaf stems, inside leaf sheaths, or on the inner surface of leaves, consuming leaf tissue. After a period of feeding, the larvae create silk threads that span between two edges of the leaf or wrap the leaf to form a shelter, causing harm inside.

When the larvae reach the 5th instar, they have the ability to construct silk shelters by folding leaves horizontally, sometimes folding 2-5 leaves into one shelter. The larvae inside the shelter can cause damage throughout the day and night. They can also move outside of the shelter to attack new leaves, and each larva can damage 5-9 leaves. The period of movement is usually in the afternoon (from 6 pm to 9 pm). On rainy or cloudy days, they can move at any time during the day.

The larvae undergo color change from green to yellowish-pink as they prepare to pupate. They can create silk threads, bite and cut two edges of leaves, and sew them back together to form a sealed shelter for pupation inside. They can crawl down to the base of the rice plant or weave a thin shelter within leaf sheaths for pupation. The majority of pupation sites are near the base of the rice plant, about 1.5cm from the water surface. Sometimes, the larvae may pupate inside the existing shelter.

Average life cycle of the small leaf roller is 28 - 36 days
Average life cycle of the small leaf roller is 28 – 36 days

The duration of each stage of larval development varies depending on the season. In general, the incubation period is 6-7 days, the duration of the larval stage is 14-16 days, the pupal stage lasts 6-7 days, and the adult lifespan is 2-6 days. The average life cycle of a small leaf roller is 28-36 days.

The harmful outbreaks of small leaf rollers are closely related to external factors. The optimal temperature range is 25-29°C with an humidity above 80%. The presence of intermittent sunshine and rain is particularly conducive to their development.

Preventive Measures

Currently, there are many products on the market to control small leaf rollers in rice plants. However, the most trusted and reputable product among farmers in recent years is Sattrungdan 95BTN by Nicotex.

Sattrungdan 95BTN is a specialized insecticide for controlling small leaf rollers in rice plants. It can also be used to prevent stem borers, leaf folders, and soybean leaf eaters.

Application Techniques

– Dosage: Use 10-15g of insecticide per 8 liters of water. Spray 2 bottles per 1 hectare in Northern Vietnam.

If the insect density is high, the dosage can be increased to 35-40g per hectare in Northern Vietnam.

– Timing: Spray the insecticide when the moths emerge or when young larvae are first seen.

– Precautions:

Do not spray the insecticide when the plants are flowering or when the leaves are wet.

Do not spray the insecticide on strawberries or near silkworm farms.

Observe a withholding period of 15 days between the last application of insecticide and harvest.

Note: Do not spray insecticides within 15 days prior to harvest
Note: Do not spray insecticides within 15 days prior to harvest

Safety Precautions

– When using the insecticide, follow safety regulations and wear protective equipment.

– After using the insecticide, wash hands and clean up properly.

– In case of accidental ingestion, seek immediate medical attention and bring the product label along.

– Dispose of packaging materials properly according to regulations.

– Store the insecticide in a cool and dry place, away from children, food, animals, and water sources.

This article provides information on small leaf rollers that we want to share with farmers. You can refer back to this information when dealing with this pest. Thank you for your attention.

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Frequently Asked Questions

1. What is the scientific name of the small leaf roller?
– The scientific name of the small leaf roller is Cnaphalocrosis medinalis.

2. What are the harmful symptoms caused by the small leaf roller?
– The harmful symptoms caused by the small leaf roller include rolled leaves, young larvae feeding on the upper surface of the leaf, and damage to the chlorophyll, resulting in reduced photosynthesis and decreased productivity.

3. What are the characteristics of the small leaf roller in its different life stages?
– The adult moth has yellowish-brown forewings with two oblique brown-black stripes. The eggs are oval-shaped with a fine network of veins. The young larvae are white and later turn green or yellow, with a light brown head. The pupa is yellow-brown and is usually found inside the rolled leaves.

4. What are the living habits and harmful effects of the small leaf roller?
– The small leaf roller is active at night and hides in the rice or weeds during the day. It lays eggs on both sides of the leaves, and the female can lay an average of 76 eggs. The larvae feed on the leaves, causing damage by rolling them into a protective cover. The whole life cycle of the small leaf roller lasts about 28-36 days.

5. What are the recommended measures to control the small leaf roller?
– A highly recommended product for controlling the small leaf roller is Sattrungdan 95BTN by Nicotex. It is applied by spraying a dosage of 10-15g of the product per 8 liters of water. The spray should be done when the moths or young larvae are present. Safety precautions, such as avoiding spraying during flowering or wet leaves, should be followed.

Emilia Chaney
Emilia Chaneyhttps://agrisearch.net
My name is Emilia Chaney. I'm a social girl from Romania with a big smile and 3 passions: Agriculture, Travel and Social Media. I try to make this blog practical, full of great advice and inspiring ideas.

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