Charlotte Pasquier, a French student at ISTOM (École supérieure d’agro-développement international), did a six-month internship with our rural development team. The aim of the internship was to complete her final year of a Masters degree in agronomy. It was within the framework of an exchange programme between the NGO Dahari and the Lycée agricole de Coconi in Mayotte that she was able to conduct her research on the island of Anjouan.
Her main mission was to carry out a study on alternative control methods to synthetic phytosanitary products against aerial pests of tomatoes, a crop that is widely consumed and grown in Anjouan.
Tomato: a crop sensitive to pests and consuming phytopharmaceutical products
Anjouanese producers face significant pressure due to the island’s tropical climate and the sensitivity of the tomato crop to pests. One of the most problematic pests is the tomato fly(Neoceratitis cyanescens), which can cause 100% losses. Other pests that can be problematic are Tuta absoluta and noctuid caterpillars, also known as moths.
To control these pests, Anjouanese producers use pharmaceutical products, sometimes excessively. This practice can lead to damage to the health of the users of the products and the consumers. It is also a practice that can cause considerable damage to the environment (loss of biodiversity, soil and water pollution, etc.).
The effectiveness of anti-insect netting and PNPPs against the use of pharmaceutical products:
The choice of these methods was made for the following reasons:
- The use of anti-insect netting is a method that has been successfully tested in Mayotte, mainly in the context of studies on the control of tomato flies.
- The use of a PNPP which has already been tested in Mayotte by the Lycée agricole de Coconi and in Anjouan by Dahari. This is a product prepared from papaya leaves and false basil, called Ntchoulé in Shidzwani.
We set up two plots with Dahari’s partner farmers. One plot was set up with the use of synthetic plant protection products and the other with the use of anti-insect netting and PNPP. We then compared the yields of marketable and non-marketable fruit. On all sites, we found that pest damage was lower under the net. The marketable yield was up to 30% higher and therefore more interesting for the growers. This was achieved with fewer plant protection products and less risk of losses due to the physical protection of the net.
On the experimental sites in Dahari, a plot was set up with the use of PNPP only (without net). We noticed that the use of the chosen PNPP alone was not sufficient to deal with pests, especially the tomato maggot.
Adoption of the anti-insect net by Anjouanese farmers
To verify the possibility of farmers adopting the method, surveys were carried out in the Nganzalé, Adda, and Ouzini areas. These surveys confirmed that the pests studied were really problematic for local producers, mainly Neoceratitis cyanescens and Tuta absoluta. They also highlighted the fact that losses were more significant during the rainy season.
Finally, the respondents seemed convinced by the use of netting and PNPPs instead of synthetic phytosanitary products. They were able to express themselves on the obstacles and advantages that this would bring them: The main obstacle stated was physical and financial accessibility and the main lever was the guarantee of a good yield and good protection against pests.
With Dahari and the Coconi agricultural college, we have been able to identify advances in alternative control methods. We will continue to experiment with the net method in combination with PNPPs with farmers to further validate these promising results.
It is important to find a net supplier to improve physical and financial accessibility. Thus, to improve the installation protocols based on the lessons learned :
- To avoid the risk of tearing the nets, installations should not be carried out under a coconut tree. Coconuts damage the structure when they fall.
- Always check the closure of the net after each visit to the plot.
- The net has a windproof effect and blocks access to the crop for pollinators. As a result, a higher number of failures are observed under the net. To avoid this, it is advisable to shake the stakes after each pass.
- It is also recommended to pay more attention to the multiplication of certain pests, especially noctuid caterpillars. In case of their presence, it is recommended to proceed with a “severe” prophylaxis, i.e. to remove the affected fruits as well as the individuals.
I was delighted to work with Dahari, a dynamic organisation that is very committed to agro-ecological agriculture in the Comoros.