Does burning stubble prevent Pink Stem Borer infestation in wheat?

Understanding the Pink Stem Borer

The Pink Stem Borer (PSB) is a notorious pest in the northern states of India, particularly in Punjab, where it thrives in the rice-wheat cropping system. PSB is most destructive during the late maturation stages of the paddy crop, attacking the rice panicles and causing significant yield loss. After harvest, the pest hides in the paddy straw and stubble, with the potential to transfer to the new wheat crop. But the real question is: does the presence of stubble really lead to a PSB attack on wheat? Experts say no.

No need to fear sowing wheat in stubble

Contrary to popular belief, sowing wheat in leftover paddy stubble does not directly contribute to PSB infestations. According to Dr Amrik Singh, Joint Director, Punjab Agriculture Department, PSB infestations are more closely linked to the timing of wheat sowing, soil moisture levels, and pest management practices than the method used to sow the wheat.

“The pest thrives under specific environmental conditions,” Dr Singh explains. “It’s the timing and conditions of wheat sowing, not the stubble, that plays a key role in preventing infestations,” he adds.

Following paddy harvesting, a 12 to 15-inch stubble remains on the field. Traditionally, this was burned to clear the way for wheat sowing. However, with the government’s push for sustainable farming practices, machines like the Happy Seeder and Super Seeder allow farmers to sow wheat without removing or burning the stubble. This method reduces air pollution and soil erosion, while also conserving moisture for the wheat crop.

“PSB completes its life cycle in 25-45 days, depending on the weather. Female moths lay eggs on leaves near the stem, and after 6-7 days, larvae hatch and bore into the stem, feeding on internal tissues. This can cause the main shoot to dry up, but the roots remain unaffected, often allowing new shoots to emerge, which can increase overall yield. However, if infestation levels exceed the economic threshold, insecticides should be used. Fortunately, no significant PSB infestation was observed in this season’s paddy crop, so the risk to wheat is expected to be lower,” said Dr Amrik Singh.

The role of timing, temperature, and moisture

Timing is critical when sowing wheat, especially if the previous paddy crop had a high incidence of PSB. Early sowing, particularly in the month of October, can increase the risk of pest attacks. According to Pargat Singh, a farmer from Bathinda, the ideal time to sow wheat is in early November, when the average temperature falls to around 22.5 degree Celsius – optimal for controlling PSB and ensuring healthy seed germination.

“Last year, I sowed wheat on November 2 using a Happy Seeder in stubble, while a neighbour burned his stubble and sowed on November 5,” Pargat Singh recalls.

“Despite sowing in standing stubble, I experienced fewer issues with PSB than the neighbour, who faced a huge attack of PSB despite burning stubble. The difference here was in the moisture levels of the soil,” he explains.

“Along with temperatures, moisture levels also play a significant role in both the health of the wheat crop and the control of pests.

While the Happy Seeder and Super Seeder are most effective when soil moisture is around 65 per cent, other machines, like the traditional till drill, require much lower moisture levels. High moisture, around 85-90 per cent, can create an ideal environment for PSB to thrive,” says Pargat Singh.

Best practices to prevent PSB infestation

While the choice of sowing method plays a minimal role in PSB infestation, proper management of timing, temperature, and moisture is essential. Farmers can also adopt the following practices to safeguard their wheat crop:

Seed treatment: Pre-treating wheat seeds with insecticides like chlorpyrifos or imidacloprid before sowing can help prevent early pest attacks.

Soil treatment: In areas with high pest populations, soil treatment with fipronil or chlorpyrifos can provide an additional layer of protection.

Daytime irrigation: Irrigating fields during the day encourages birds to feed on PSB larvae, naturally reducing pest numbers.

Post-irrigation treatment: If PSB infestation is noticed after the first irrigation, farmers should apply treatments like chlorantraniliprole to curb the spread.

With the right approach, experts say, Punjab’s wheat farmers can overcome the challenges posed by PSB, ensuring a healthy and bountiful crop season.