LEAF ROLLER AND CONTROL MEASURES

Small rice leaf roller is a widespread rice pest, often occurring and causing damage during the tillering, panicle initiation, and flowering stages. Leaf rollers cause damage to rice all year round, commonly occurring in the winter-spring and summer-autumn crops. If there are no good control measures, they will cause serious damage to farmers.

What is small rice leaf roller?

The small rice leaf roller has the scientific name Cnaphalocrocis Medinalin, belongs to the family Pyralidae, order Lepidoptera. This is a rice pest that often causes large and severe epidemics in many rice growing areas of our country. The worm often blooms and causes severe damage over a large area during the tillering, panicle initiation and flowering stages.

Morphological characteristics of rice leaf roller

• Adult: yellowish brown, front edge of forewings has two oblique black-brown streaks. Active mainly at night, lays eggs scattered on rice leaves.
• Eggs: oval, opaque white, then turn yellow when about to hatch.
• Larva: 5 instars, green or orange-yellow, light brown head. Larvae are mobile and cause damage to many rice leaves.
• Pupa: yellow-brown in color, often found in rolled rice leaves.

Life cycle of rice leaf roller

The life cycle of the small leaf roller that damages rice plants is on average about 28 - 35 days, depending on weather conditions, fertilizers and rice varieties. In which:

– Butterfly lives from 2 – 4 days

– Egg stage from 6 – 7 days

– Larva from 14 – 21 days

– Pupa lives from 6 – 7 days

Characteristics of damage caused by small leaf rollers on rice plants

Leaf rollers cause damage by rolling and eating leaves. The newly hatched first instar larvae usually lie in old damage wounds or crawl to the top of the leaf.

The second instar larvae begin to cause damage by spinning silk to roll the two edges of the leaf into a tube, living and causing damage inside by biting the green tissue containing chlorophyll, leaving the epidermis on the underside of the leaf, so the fields damaged by leaf rollers look silvery and withered.

Because the leaves are rolled and lose chlorophyll, photosynthesis is reduced, causing the rice to become flat and stunted, reducing yield. In addition, the wound on the edge of the leaf is also a path for bacteria that cause bacterial leaf blight and bacterial streaks to invade and cause damage, especially during storms and strong winds.

Usually, we only find one leaf roller in a leaf and after causing damage, the worm crawls to the next leaf and continues to bite and destroy, on average one worm damages about 3 - 5 leaves.

The period of 40 days after sowing is considered the most suitable for all instar larvae.

Measures to prevent leaf rollers

To effectively manage rice leaf rollers, farmers should combine many measures: if possible, only grow 2 rice crops or rotate rice with other crops, do not sow too densely, apply balanced fertilizer and pay attention not to apply too much nitrogen fertilizer to avoid the situation of rice leaves being lush and too green, attracting leaf rollers to the field. Weeds should be cleared on the banks because that is where leaf rollers live.

Limit spraying in the first 30 days after sowing to protect natural enemies in the rice field and at this time the rice plant is also in the leaf growth stage so it has the ability to recover, without losing productivity. However, if the density of leaf rollers appears to reach the action threshold, that is, about 30 insects/m2, farmers should apply the last measure, which is spraying the leaves. Particularly in the heading - flowering stage, the density of leaf rollers is about 6-9 insects/m2, so spraying must be done immediately to ensure rice productivity.

Determining the presence of leaf roller moths in the field is very necessary. Normally, after seeing butterflies in the field, after 6-7 days, the first instar caterpillars will hatch, this is the most suitable time to spray pesticides because the caterpillars are still young so they are very easy to treat. Next is to choose the right type of pesticide to kill leaf roller moths. Third is the right way, spray the pesticide evenly, enough for the pesticide to contact the caterpillars. Finally, spray the correct dosage as recommended when the caterpillars are instar 1-2 to be both effective and cost-saving.

Manh Dan Joint Stock Company brings farmers the MDmetometa 400SC solution for effective pest control. MDmetometa 400SC is a new generation pesticide, with a golden ratio mixing formula, with a nerve-acting mechanism & promoting the molting process with maximum effectiveness after 3 days, long-lasting effect. Many farmers in the Mekong Delta have used MDmetometa 400SC on rice when the worms are 1-2 years old with a dosage of 30ml/25L tank to achieve high efficiency and optimize costs.

For more information about the product and effective pest management, please contact 0867 487 988 or send a message directly via the Manh Dan fanpage.