AUTHORITIES in Zimbabwe and Zambia must closely monitor the recent army worm outbreak in the two countries to determine the impact it may have on food security, the United Nations World Food Programme (WFP) says.

Army worms are moth caterpillars that, when present in large numbers, can destroy large areas of vegetation and crops. The outbreak, along with a delayed start to the rainy season, could further damage food security in the two countries.

The army worm infestation struck in Zambia in December. The price of maize in Zambia had already nearly doubled to $15.21 (80 kwacha) the previous month.

Authorities in Zambia have managed to bring the outbreak under control but have urged farmers to remain vigilant.

WFP public information officer Claudia Altorio said on Tuesday that it was still too soon determine with certainty the impact the army worms may have on food security.

"In Zambia, the forecast of the spread and its severity will be influenced by weather in the coming weeks. The degree of impact will depend on the rain and weather, and we are closely monitoring it," Ms Altorio said.

The Zambian government and the WFP are assisting more than 1-million people in an effort to safeguard livelihoods and ensure children and those living with HIV and AIDS have adequate nutrition.

Affected areas received seed and pesticide in the government-led response that began in mid-December.

The WFP has finished providing technical assistance to the Disaster Mitigation and Management Unit on a paper voucher distribution mechanism used to distribute seed to 25,000 farmers in Chongwe, in Lusaka province.

In December the Zambian agriculture and livestock ministry advised farmers to buy chemicals including Malathion, Diazion and Cypermethrin for spraying.

With Reuters