Instructions for preventing brown planthoppers in rice

The brown planthoppers suck and burn the planthoppers and also transmit dangerous diseases such as yellow dwarf and leaf curled dwarf. Effective prevention requires sparse sowing, avoiding leafhoppers, balanced fertilization, protecting natural enemies and only spraying when the population exceeds the threshold.

Summary: Brown planthoppers are dangerous pests on rice because they both suck and weaken the plant and transmit yellow stunt and twisted leaf stunt diseases. Many fields are severely damaged not due to lack of crop-protection products, but due to thick sowing, excess nitrogen fertilization and early spraying that destroys natural enemies. Management of brown planthoppers needs to start from the crop schedule and sowing density, not waiting until the field burns before treating them.

Applies to: paddy fields in areas with brown planthopper pressure, especially where rice production is continuous.
Duration: Monitor throughout the season, focusing from tillering to flowering — ripening.
Difficulty level: Medium. Need to visit fields and handle according to threshold.
Estimated additional costs: Varies according to hopper population; Good prevention is often cheaper than fighting pest fires.

Identify brown planthoppers

Brown planthoppers have a life cycle of about 23-30 days, spending 5 years as young hoppers before becoming adults. Newly hatched leafhoppers are gray-white, then from age 2-3 gradually turn yellow brown.

Adult leafhoppers have two forms:

Long wings: moves long distances, can fly with the wind and is attracted by lights at night.
Short wings: reproduces strongly in the field, causing population to increase rapidly.

Both young and adult leafhoppers suck sap from rice plants at the base. When the density is high, the tree turns yellow and gradually dries out in clusters and then spreads into leafhopper fire.

Harmful effects of brown planthoppers

Brown planthoppers cause damage in two ways.

Prickling causes the tree to decline

Aphids gather at the base of the rice, sucking sap, causing the plant to lose its strength. When the density is high, the rice leaves quickly turn yellow, the plants dry, and the entire field can burn into pieces.

The flowering and ripening stages are often severely damaged because the honey has accumulated since the beginning of the season. If detected late, rice will have difficulty recovering and productivity will decrease clearly.

Transmitting dangerous diseases

Brown planthoppers are vectors for transmitting diseases such as:

Dwarf yellow.
Dwarf twisted leaves.
Weedy rice and some virus-related disorders.

When the field is infected with a virus disease, spraying insecticide to kill planthoppers will not make the diseased plants green again. Therefore, preventing aphids from migrating and sowing seeds to avoid aphids is very important.

Conditions that cause brown planthopper outbreaks

Brown planthoppers often thrive when there are many favorable factors at the same time:

Continuous rice production all year round, no crop cutting time.
Sowing is not done at the same time, alternating old and young fields.
Use aphids-infected varieties or hypersensitive varieties.
Thick sowing, dense fields.
Excess nitrogen fertilization makes green rice soft.
Spray crop-protection products early within 0-40 days after sowing.
Mixing many types of drugs and spraying many times kills natural enemies.

A dense green field with few natural enemies and always having young rice around is a very easy condition for leafhoppers to increase their population.

Prevent leafhoppers from the beginning of the season

Use suitable varieties

You should choose certified varieties that are resistant to brown planthoppers if the area frequently has epidemics. You should not plant seeds from fields that have been infected with leafhoppers or yellow dwarf disease.

Sow at the same time and avoid leafhoppers

Comply with local seasonal schedules. When the whole area is sown at the same time, it is difficult for leafhoppers to have a continuous food source. Sowing to avoid peak leafhopper migration also helps reduce the risk of disease transmission early in the season.

Sow sparsely, sow every

Sparse sowing or row sowing helps the field to be airy, natural enemies work better and it's easier to check rice roots. Thickly sown fields are often places where leafhoppers hide and reproduce quickly.

Field cleaning

Before and during the crop, it is necessary to clear rice debris, weeds and diseased rice plants around the field. This may be where leafhoppers and pathogens survive between crops.

Manage fertilizer to limit leafhoppers

Excess nitrogen fertilization makes rice green and soft, very attractive to brown planthoppers. You should fertilize with a balance of nitrogen, phosphorus, and potassium and use the leaf color chart to decide whether you need to add nitrogen or not.

Principle:

Do not fertilize with nitrogen based on your feelings because the field next to you feels greener.
Do not fertilize strongly when the field has a high population of leafhoppers.
Increase potassium if soil and growth stage need it, helping plants become harder.
Monitor leaf color, don't let the field stay dark green for too long.

Proper fertilizer management does not kill leafhoppers directly, but farming is less attractive to leafhoppers and plants are stronger when exposed to pest pressure.

Protect natural enemies

Natural enemies are the forces that keep leafhoppers at a low level. In paddy fields there are often spiders, ladybugs, parasitic wasps and many other predators.

To protect natural enemies:

Do not spray crop-protection products for 0-40 days after sowing if not necessary.
Do not spray broad-spectrum crop-protection products on a fixed schedule.
Do not mix multiple medications just "to be sure".
Keep field edges with suitable vegetation to support natural enemies.
Can apply ecological techniques or biological products such as Metarhizium sp. when appropriate.

When there are many natural enemies, leafhoppers are often naturally controlled. Spraying crop-protection products early will upset this balance, and then leafhoppers may have a stronger outbreak.

When to use chemical drugs

Should only be sprayed when planthoppers reach high populations, about 2,000-3,000/m2 or according to local recommended thresholds. It is necessary to check at the base of the rice, because leafhoppers often lie low, not on the leaf surface.

Some active ingredients often recommended in preventing brown planthoppers include:

Abamectin.
Emamectin benzoate.
Pymetrozine.
Buprofezin.

Before spraying, water should be added to the field to help the hoppers move higher, increasing the possibility of contact with the drug. Spray at the right dose, at the right time and rotate active ingredients to limit drug resistance.

Don't spray when the density is still low just because you're worried. That method both costs money and reduces natural enemies.

Checklist for visiting brown planthopper fields

[ ] Check the rice roots, not just the leaves.
[ ] Monitor juvenile and adult leafhoppers.
[ ] Observe natural enemies before deciding to spray.
[ ] Record the number of leafhoppers at each point in the field.
[ ] Check carefully the flowering — ripening stage.
[ ] Do not spray for 0-40 days after sowing if the threshold has not been exceeded.
[ ] When you need to spray, apply water to the field and choose the correct active ingredient.

Common mistakes

Sow thickly and then depend on crop-protection products: dense fields make it easy for leafhoppers to increase their population, and spraying crop-protection products makes it difficult to reach the roots.

Spraying at the beginning of the season according to schedule: kills natural enemies, making leafhoppers more likely to break out later.

Only look above the foliage: leafhoppers are located at the base, otherwise checking the base line will detect late.

Add nitrogen when the field is infested with aphids: green plants become softer, aphids grow faster.

Wait until the hopper burns before treating: by that time the tree is exhausted, the effectiveness of saving the field is low.