IITA records breakthrough against pest devastating African cabbage

African cabbage farms ravaged by Diamondback moth (DBM), Plutella xylostella, are set to make a come back as a biocontrol-pesticide (Beauveria bassiana) developed by scientists at the International Institute of Tropical Agriculture records a huge success in the control of the pest.

Resource-poor farmers said the biocontrol method has proved effective in controlling the insect pest that has devastated both smallholder and large-scale cabbage farms in Africa.

“From a disappointment in cabbage production, we now have the hope of promising results obtained using B. bassiana,” says Mr. Raymond Ahinon, an official at Songhai Center—a center for training, production, research-for-development of sustainable agricultural practices—in Porto Novo, Republic of Benin.

“The product is effective, and has helped in controlling DBM on our cabbage farms” says Ahinon, who heads the Crop Department of Songhai Center.

Cabbages are among the most important vegetables in Africa in general and Benin in particular especially for lower income farmers. The importance of this vegetable is probably greater as it acts as a stream of income among farmers most affected by poverty including small farmers, youth, and most especially, women who paradoxically play an important role in agricultural production.

Eaten daily, either raw in salads, steamed, boiled or fried, cabbages and their cousin kale serve as important cash-generating crops.

Despite the importance of the crop, destructions by DBM on cabbage farms have forced thousands of farmers in West Africa to abandon cabbage production for other crops.

The situation is worsened by the high costs associated with synthetic pesticide that serves as chemical control option.

“The most common synthetic chemical pesticides used by farmers are bifenthrin and deltamethrin,” says Dr. Ignace Godonou, IITA Entomologist.

“About 19 applications of these chemicals are needed within three months of the crop growth prior to harvest. Besides, acquiring these chemicals comes with a cost sometimes prohibitive.”

On a global scale, chemical control is estimated to cost about $1billion annually with a package of health and environmental risks, which include pollution, destruction/death of non-target including useful insects and therefore the reduction of biodiversity.

In recent years, chemical control of DBM is proving ineffective, according to farmer Louis Awandjinou, who has been cultivating the crop since 1986.

Dr. Godonou says the pest has developed resistance to a wide range of synthetic insecticides.

But the good news is that the biopesticide, B. bassiana, in an integrated pest management approach offers a solution to sustainable control of DBM, he adds.

So far resource-poor farmers use botanical pesticides, mostly seed extracts of the neem tree against DBM and a wide range of other arthropod pests but the success of this approach has been limited.

In search of sustainable biological agents to control the pest, Dr Godonou says eight isolates of the entomopathogenic fungi B. bassiana and Metarhizium anisopliae indigenous to Benin were screened for virulence against larvae of the insect out of which two isolates held promise.

One of the isolates Bba5653 caused 94 percent mortality of DBM larvae and mortality was significantly higher than that caused by any other of the isolates. Cabbage yield in plots treated with Bba5653 was approximately three fold higher than the yield in plots treated with the insecticide bifenthrin or in untreated plots.

According to Godonou et al. in a study published in Crop Protection journal in 2008, B. bassiana and M. anisopliae are ubiquitous in nature, generally specific to target pest, persists in the environment and easy to mass produce.

Mr. C. Atcha-Ahowe, IITA scientist who co-authored the results on B. bassiana in the Crop Protection journal says field trials of the biopesticide have sparked demand for the commodity.

“Majority of farmers that abandoned cabbage cultivation for other crops are now requesting the biopesticide to make a come back but the problem is the availability of the product,” he says.

When compared to other vegetable crops such as carrots and lettuce, resource-poor farmers say returns are higher in cabbage cultivation. The gap is exacerbated by increasing demand amid dwindling supply of cabbage.

Like the Green Muscle® which was picked up by the private sector, Dr. Godonou says the B. bassiana technology is another opportunity in the waiting for the private sector.

He says farmers will be willing to patronize the product to control the cabbage enemy and boost yield.

“With the ability to remain active on the field for several months after initial application, B. bassiana will end the rigor of repetitions and cost associated with synthetic chemical pesticides,” he adds.

GHANA / AFRICA / MODERNGHANA.COM