Farmers in Nyanza and Western provinces lose maize worth more than Sh1.8 billion to the deadly striga weed annually.
Experts on Thursday warned that the weed was posing a threat to food security in the region, as it affects more than 540,000 acres of crops every season.
Prof George Odhiambo of Maseno University said striga was a major problem in the two regions where most families depend on maize as staple food.
Striga, known in Nyanza as kayongo and Oluyongo in Western, affects maize, millet, sorghum and rice production leading to loses of 180,000 tonnes.
Odhiambo said effects of the weed were so immense that in a one-hectare farm a farmer can only harvest 500kg of maize instead of 5,000.
"But under heavy infestation of a farm by striga, a farmer could get zero yield," he added.
He was speaking during a striga weed demonstration site at Aboke in Ugenya constituency where farmers were trained on modern techniques to fight the wild plant.
The demonstration was organised by the implementing agency in Kenya, the Organisation for Transforming Initiated Technologies, which was represented by its director Mr Emmanuel Opil and programme officer Ms Joan Mwanga.
Odhiambo said the demonstration sites spread across Nyanza and Western were being implemented as a programme to fight striga under the Integrated Striga Management in Africa focusing on Kenya and Nigeria and funded by the Bill and Melinda Gates Foundation.
The sites are in Siaya, Teso, Busia, Kisumu, Rachuonyo and Migori.
He said the programme had also introduced the Desmodium plant that is grown between rows alternate with maize to help fight striga weed.
"We are also encouraging farmers to use seeds that are striga resistance or striga tolerance such as legume crops that act as a trap for the weed," he added.
He explained that striga can only be controlled through integrating several techniques to reduce the weed in the farms.
Odhiambo who was accompanied by other experts from Icipe, said a striga tolerance sorghum variety was also being introduced into the market and would soon be released by the Kenya Seed Company.
He advised farmers who uproot the weed from their farms not to throw them along the way as they would be washed back by rains.
"The only alternative is to heap them together and burn them," he said.