The Delhi government on Thursday issued a circular with a list of preventive measures that should be taken to keep swarms of locusts away, The Indian Express reported. Locusts, which destroy crops, have invaded vast swathes of land in western and central India over the past few days.

“As the swarms usually fly in the day time, the locust should not be allowed to rest at night,” the advisory, issued by Joint Director of Agriculture AP Saini said. The advisory also said that four chemicals – Melathion 50% EC, Melathion 25% WP, Chloropyriphos 20% EC and Chloropyriphos 50% EC – should be diluted in water and sprayed as pesticides on crops in the evening to prevent locust attacks.

Delhi’s Labour Minister Gopal Rai convened a meeting at his residence to discuss preparations being made to combat the locusts, ANI reported.

The Centre on Wednesday stepped up its response to the threat of locusts. This came after experts warned of extensive crop losses if authorities fail to contain the fast-spreading swarms by June.

In a statement, the Ministry of Agriculture said control operations have been stepped up and drones will be deployed for aerial spraying of insecticides in the affected states. Locust containment measures and sprinkling operations have been conducted in 303 locations spread over more than 47,000 hectares till Wednesday in 21 districts of Rajasthan, 18 in Madhya Pradesh, two in Gujarat and one in Punjab, it added.

The government has also placed an order for 60 spraying machines from United Kingdom-based company Micron, and two firms have been finalised to supply drones for aerial spraying of insecticides over tall trees and inaccessible areas.

“We are controlling the locust swarms on a daily basis but they cannot be controlled in one go because they are escaping,” Locust Circle Offices Deputy Director KL Gurjar said. “They are going forward.” However, he said there is no possibility of the insects moving towards Delhi because “the wind current is different”.

This is the worst locust attack in decades as they are spearing into Maharashtra, Uttar Pradesh and Punjab after destroying crops in Rajasthan, Gujarat, Madhya Pradesh and Haryana.

Scientists believe there is a connection between climate change and locust attacks. Locusts thrive in wet conditions, with attacks following cyclones and floods. As greenhouse gases continue to heat the ocean and the atmosphere, floods and cyclones are becoming more common, increasing the possibility of frequent locust attacks.