Case study Identity Card

Long title: White grub control, Biocontrol of a white grub in sugarcane
Geographical coverage of the case: Reunion island (France)
Case study team: Regis Goebel (CIRAD, Aïda), Pierre Martin (CIRAD, Aïda), Estelle Roux (FDGDON), Jean-Marie Paillat (CIRAD, Recycling and risks), Nans Mouret (Istom, intern)
Years covered: 1981-2007

Case study description

The innovation under study: Control of the sugarcane white grub in Réunion, a success story

From 1981, when it first appeared in Réunion, to 2007, the white grub was the focus of research teams at CIRAD. To reduce the economic impact of this sugarcane pest, every effort was made to achieve effective, operational biological control, ensuring sustainable protection of the sugarcane industry, which was under threat. An overview of 15 years of control.

The white grub first began to cause damage to sugarcane crops in Réunion in 1981. This grub is the larva of the beetle Hoplochelus marginalis. It develops in the soil, feeding on the roots of sugarcane, but also of numerous other crops and plant species (grass, pineapple, strawberry, etc.). It is thought to have arrived in 1973 in the luggage of French soldiers travelling from Madagascar, and it took eight years to see the first damage in sugarcane fields. Between 1985 and 1990, yield losses reached 15% of production and, in 1990, economic damages were estimated at around two million euros.

An entomopathogenic fungus to control the white grub

As soon as this pest first appeared, the public authorities convened all stakeholders: agricultural organisations, public actors and research centres, especially IRAT, which became part of the newly formed CIRAD several years later. The researchers based in Reunion tested several different cultural and chemical control techniques, with varying degrees of success. In 1982, they decided to associate insecticides and biological control. Once again, the results were disappointing. From 1987 onwards, they decided to test a new insecticide, Suxon, which had been successfully used in Australia to control other grub species This product was effective when applied during replanting, but only remained active in the soil for three years, whereas the sugarcane was replanted every five to seven years.

At the same time, the researchers conducted tests with an entomopathogenic fungus, Beauveria tenella, a species native to Madagascar, like the white grub found in Réunion. The results were excellent: good acclimatisation, a high level of parasitism, and continued efficacy after several years. This success led them, in 1994, to patent the strain of B. tenella entomopathogen of H. marginalis under the name Beauveria brongniartii.

The thorny issue of application techniques

In 1989, rice grains coated with spores of B. brongniartii were produced on a small scale and distributed by FDGDON, the departmental plant protection organisation. In order to infect the insects, adults were dipped in a “sporised” rice-based solution and then these contaminated insects were released to pass on the fungus to other insects. This method was used until 2002.

At the same time, the researchers tested another application method: sporised rice was scattered directly in the furrows during sugarcane replanting. But this technique was rapidly abandoned despite its effectiveness, as it was impossible to produce enough sporised rice to cover the whole territory.

Betel, an immediate success

In 1995 this technique gained new popularity, with Betel®. Betel is composed of clay balls containing spores of B. brongniartii, which are placed in furrows during replanting. It was developed with the technical support of researchers and produced on an industrial scale by the company Bétel Réunion. The Réunion departmental council subsidised its use, as with the other control methods.

Combined with Suxon, Betel effectively protected sugarcane plantations: the insecticide had an immediate effect, which persisted for the first three years, the time needed for the entomopathogen to spread into the soil. Suxon applications could then be reduced by 75%. In 2004, this insecticide was banned, the assumption being that the entomopathogen was now present in plantations and could simply be reactivated during replanting.

An overview of 15 years of control

In 2015, CIRAD took stock of this research in order to evaluate its impacts on all levels of the sugar industry with hindsight. This study combined interviews, statistical data and critical analyses.

The researchers thus conducted more than 60 individual interviews with planters, but also carried out surveys among professionals in the sugar industry, field staff, administrative staff and elected officials.

A second wind for sugarcane production

The first impact of this innovation was, of course, the end of damage caused by the white grub. This is confirmed not only by interviews with local people but also by data on beetles caught. According to information collected by FDGDON, the number of larvae per sugarcane stump fell from 1.4 in 1996 to fewer than 0.2 in 2014, while the parasitized larvae rate reached 40%.

Once threatened by infestation, the viability of plantations now guaranteed, and the sugar industry is resuming normal activity.

Distributors of crop protection products adapting their range to this new protection method, and the Bétel company is growing , with a steady increase in turnover since 2001.

An environmentally friendly industry

The second impact, which is beneficial to the environment, is the phasing out of insecticides, an impact that is quantifiable not only through insecticide applications prescribed, but also through quantities sold: between 1989 and 1997, sales of Suxon stood at 100 tonnes per year, before falling to 20 tonnes and ceasing completely in 2005. The quantities of chlorpyrifos-ethyl, the active ingredient in Suxon, found in water and soils also decreased from the beginning of the biological control process, as shown by samples taken by the Office de l’Eau.

In addition to this direct impact on the environment, there is also an indirect impact on the sugar industry, whose image has improved: its sugar products are now healthier since they do not contain insecticides.

Biological control, an ongoing dynamic for new initiatives

The success of biological control has also created a dynamic on the island, with the launch of 13 new projects and the creation of a private company specialising in biocontrol.

It has also improved the reputation of the local authorities in this field: FDGDON was tasked with an international project and the departmental council received an award in 2009 for its actions on sustainable development, among others in the field of agriculture.

Actors involved in the innovation

Stakeholders involved in the innovation process

Value chain stakeholders: Betel Reunion, CTICS (inter-professional technical center of sugar and cane in Reunion Island), Regional Chamber of Agriculture, SICA (agricultural cooperatives), Sugar manufacturers, Sugarcane producers, Sugar syndicate.
Research stakeholders: CERF (anterior to eRCANE), Cirad, Fofifa, Inra,  University of La Réunion
Civil society stakeholders: Private individuals
Institutional stakeholders: DAAF, Conseil Général de La Réunion, Mauritius Government, the French Ministry of Research and Toxicology, the French Ministry of Agriculture, City halls of La Réunion
Others: Botanica, Calliope NPP, FDGDON, Mass media, Private distributors of Betel product, Sofider Bank

Stakeholders impacted by the innovation process

Value chain stakeholders: Sugarcane producers, Sugar manufacturers, Betel Reunion
Civil society stakeholders: Private individuals,
Institutional stakeholders: Conseil Général de La Réunion
Other: FDGDON