Weeding in cassava is a tortuous and back-breaking exercise that limits the ability of farmers to expand their cropped area.
However, scientists working with the African Cassava Agronomy Initiative (ACAI) of the International Institute of Tropical Agriculture (IITA) have identified some post-emergence herbicides that farmers can use during the growing period of cassava to tackle weeds.
These post-emergence herbicides, though not exclusive to cassava, have been adopted in the framework of the Six Steps to Cassava Weed Management and Best Planting Practices toolkit for use in cassava to control weeds.
In Nigeria, post-emergence herbicides include glufosinate ammonium, which is currently branded as Lifeline, Slasha Gold, Basta, etc., says Prof. Friday Ekeleme, Principal Investigator on Weed Control Measures in IITA.
“But fluazifop-p-butyl branded as Fusilade forte etc. can also be applied if the weeds in the cassava field are grasses,” he added.
How is the post-emergence herbicide applied?
The application of post-emergence herbicides requires care and skill to avoid damage to the cassava.
This is because the post-emergence herbicides used in cassava are not selective, meaning that they will harm cassava if they come in contact with the green parts of the cassava crop, including the green stems and the leaves.
“To avoid the post-emergence herbicides touching the green parts of cassava, farmers are encouraged to use spraying shields that are usually attached to the nozzle of the sprayer,” Prof. Ekeleme said.
“There is, however, an exception, and that is Fusilade Forte… Fusilade Forte can be applied directly to the cassava crop to kill grasses (narrow leaf weeds only).
“If the field has a combination of both narrow and broad-leaf weeds, apply glufosinate ammonium,” he explained.
Six Steps to Cassava Weed Management & Best Planting practices
Researchers in IITA have packaged the knowledge on the use of post-emergence and pre-emergence herbicides in cassava farming systems into an extension toolkit known as the Six Steps to Cassava Weed Management & Best Planting practices (simply called ‘Six Steps’), for dissemination to farmers.
The ‘Six Steps’ is a set of agronomic recommendations including tillage and plant nutrition that enables farmers to grow cassava (or cassava intercropped with maize) with minimal interference of weeds, thereby pushing up the yield threshold of cassava.
According to IITA Digital Extension and Advisory Services Specialist, Godwin Atser, who is leading the dissemination of the ‘Six Steps’ toolkit, farmers are advised to apply post-emergence herbicides only when the cassava crop is eight weeks old and above.
Besides, post-emergence herbicides should be applied when weeds cover 30 per cent of the field, and they are at 4-6 leaf stage.
IITA Director for Development and Delivery, Dr Alfred Dixon, also called on farmers to follow the ‘Six Steps’ for optimum control of weeds, stressing that the toolkit comprises all the recommendations necessary for weed control.
He stressed that the effective control of weeds was crucial for higher cassava productivity and urged farmers to contact IITA for the toolkit for use on their farms.