By Sandra Chukwunyere
Weeding in cassava is a tortuous and a 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 postemergence herbicides that farmers can use during the growing period of cassava to tackle weeds.
These postemergence herbicides, though not exclusive to cassava, have been adapted in the framework of the Six Steps to Cassava Weed Management & Best Planting Practices toolkit for use in cassava to control weeds.
In Nigeria, postemergence herbicides include glufosinate ammonium, which is currently branded as Lifeline, Slasha Gold, Basta, e.t.c., says Prof. Friday Ekeleme, Principal Investigator on weed control measures in IITA. ”But fluazifop-p-butyl branded as Fusilade forte e.t.c. can also be applied if the weeds in the cassava field are grasses,” he added.
How is the postemergence herbicide applied?
The application of postemergence herbicides requires care and skill to avoid damage to the cassava. This is because the postemergence 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 postemergence 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 postemergence and preemergence 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.
ACAI has further bundled the toolkit into AKILIMO—a one-stop-shop advisory tool for farmers.
According to IITA Digital Extension and Advisory Services Specialist, Godwin Atser, who is leading the dissemination of the ‘Six Steps’ toolkit, farmers are being advised to apply post-emergence herbicides only when the cassava crop is 8 weeks old and above.
Besides, postemergence herbicides should be applied when weeds cover 30 percent of the field, and they are at 4-6 leaf stage.
IITA Director for Development & Delivery, Dr Alfred Dixon, 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 the use on their farms.