Corn seedling are pictured in a cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Yu Wuyang, an ethnic Dai farmer, picks corn in his cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

An ethnic Dai boy attempts to capture a butterfly, at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Yu Wuyang, an ethnic Dai farmer, picks corn in her cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Corn crops hit by armyworm in a field in Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Corn crops hit by armyworm in a field in Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Yu Wuyang, an ethnic Dai farmer, picks corn in her cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Yan Wenliu, 36, sprays pesticides at a sugar cane field at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

A farmer sprays pesticides at a sugar cane field at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song

Corn crops hit by armyworm in a field in Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

An ethnic Dai farmer picks corn in her cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Yan Wenliu's wife prepares to spray pesticides at a sugar cane field at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

Plant leaves hit by armyworm are seen next to a cornfield in Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Packs of pesticides are pictured next to a cornfield in Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Mr. Yao, sales manager based in Xishuangbanna, for Jingbo Agrochemicals Technology Co. Ltd., inspects corn crops hit by armyworm in a field in Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d u000d

A farmer prepares to spray pesticides at a sugar cane field at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

Yan Wenliu, 36, and his wife spray pesticides at a sugar cane field at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

Yu Wuyin, an ethnic Dai farmer, stands in her cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

An ethnic Dai farmer stands in her cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

Yu Wuyang, an ethnic Dai farmer, walks in her cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song

Yan Wenliu's wife prepares to spray pesticides at a sugar cane field at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

Stunted corn are pictured inside a rattan basket in a cornfield at Nuodong village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 13, 2019. Picture taken July 13, 2019. REUTERS/Aly Song u000d

An armyworm, which usually comes out at night, is seen on corn crop at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

An armyworm, which usually comes out at night, is seen on sugar cane crop around dusk at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

An armyworm, which usually comes out at night, is seen on sugar cane crop around dusk at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

An armyworm, which usually comes out at night, is seen on sugar cane crop around dusk at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

Yan Wenliu's wife prepares to spray pesticides at a sugar cane field at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

A farmer sprays pesticides at a sugar cane field at a village of Menghai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song u000d

The fall army worm has spread rapidly across Asia since its arrival in India in July 2018. Map showing areas suitable to fall armyworm invasion.

The fall army worm has spread rapidly across Asia since its arrival in India in July 2018. Map showing spread of the fall armyworm.

A farmer shows a Fall Army Worm in a maize field at Pak Chong district, Nakhon Ratchasima province, Thailand June 12, 2019. Picture taken on June 12, 2019. REUTERS/Soe Zeya Tun

A farmer shows a Fall Army Worm in a maize field at Pak Chong district, Nakhon Ratchasima province, Thailand June 12, 2019. Picture taken on June 12, 2019. REUTERS/Soe Zeya Tun

Workers spray insecticide at a maize field destroyed by Fall Army Worm at Pak Chong district, Nakhon Ratchasima province, Thailand June 12, 2019. Picture taken on June 12, 2019. REUTERS/Soe Zeya Tun

A farmer shows a Fall Army Worm in a maize field at Pak Chong district, Nakhon Ratchasima province, Thailand June 12, 2019. Picture taken on June 12, 2019. REUTERS/Soe Zeya Tun

A farmer shows a Fall Army Worm in a maize field at Pak Chong district, Nakhon Ratchasima province, Thailand June 12, 2019. Picture taken on June 12, 2019. REUTERS/Soe Zeya Tun

A farmer looks around his maize field destroyed by Fall Army Worm at Pak Chong district, Nakhon Ratchasima province, Thailand June 12, 2019. Picture taken on June 12, 2019. REUTERS/Soe Zeya Tun

A maize field destroyed by Fall Army Worm is seen at Pak Chong district, Nakhon Ratchasima province, Thailand June 12, 2019. Picture taken on June 12, 2019. REUTERS/Soe Zeya Tun

A worker sprays insecticides at a maize field destroyed by Fall Army Worm at Pak Chong district, Nakhon Ratchasima province, Thailand June 12, 2019. Picture taken on June 12, 2019. REUTERS/Soe Zeya Tun

A farmer shows a corn shoot infested with fall armyworm at his farm in Narayangaon village in the western state of Maharashtra, India, December 18, 2018. Picture taken December 18, 2018. REUTERS/Rajendra Jadhav

A farmer inspects his crop as they are bracing for severe crop damage from an invasion of the crop-eating armyworm at a farm in Settlers, northern province of Limpopo, February 8,2017. REUTERS/Siphiwe Sibeko

A crop-eating armyworm is seen on a sorghum plant at a farm in Settlers, northern province of Limpopo, February 8,2017. REUTERS/Siphiwe Sibeko

A leaf of a sorghum plant is seen after it was eaten by a crop-eating armyworm at a farm in Settlers, northern province of Limpopo, February 8,2017. REUTERS/Siphiwe Sibeko

A crop-eating armyworm is seen on a sorghum plant at a farm in Settlers, northern province of Limpopo, February 8,2017. REUTERS/Siphiwe Sibeko

A crop-eating armyworm is seen on a sorghum plant at a farm in Settlers, northern province of Limpopo, February 8,2017. REUTERS/Siphiwe Sibeko

A worker uses a tractor to spray a field of crops during crop-eating armyworm invation at a farm in Settlers, northern province of Limpopo, South Africa, February 8,2017. REUTERS/Siphiwe Sibeko