Photo: Shutterstock Many farmers in northern Bangladesh have failed to apply organic pest control in their eggplant crop. They continue to use substantial amounts of pesticides on a weekly basis to deter the eggplant root and shoot borer (Leucinodes orbonalis). Environmentally friendly alternatives are known but remain a theoretical possibility for the eggplant farmers.
PhD candidate Naznin Nahar worked with the farmers to inventory what the major plant diseases were. This showed that there are two fungal diseases and brown rot to contend with, in addition to the eggplant root and shoot borer. The farmers applied chemical pesticides for those other diseases as well, without success. Literature recommended a combination of organic agents, but these had not all been tested in the field. Thus, Nahar initiated field experiments with the farmers.
No added value
She began with the propagation of the eggplant sprouts, where a soil fungus afflicted the plants. By treating the seeds with hot water and ousting the pathogen with the beneficial soil fungus Trichoderma harzianum the number of sprouts that propagated was increased by 25 to 64 per cent compared to the use of chemical substances. It became clear that farmers could also combine the beneficial soil fungus with the chemical agent. Following this, she tested these stronger seedlings for brown rot. This showed that the T. harzianum fungus had a positive effect on suppressing the brown rot bacteria. She advised the farmers to apply this fungus to the larger fields, but its use is costly.
Literature suggested a combination of pheromone traps and removal of affected shoots and fruits to combat the eggplant root and shoot borer. Farmers immediately rejected the second option, considering this too labour intensive. They wanted to combine pheromone traps with conventional spraying. Thereupon, Nahar suggested organic agents that could be sprayed with far less damage to the environment. This combination increased the farmers’ yield and thus, income. After the test-year, the farmers stopped using the pesticides, as they had no added value in combatting the root and shoot borer.
People management
Nahar’s research provided the farmer with a menu of options, rather than a strict protocol. Thus, the farmers were able to ascertain through experimenting whether Integrated Pest Management might be effective for them, and what options fitted them. Organic pest control is certainly possible, but only in combination with integrated people management, Nahar concludes. She obtained her PhD under Paul Struik, professor of Plant Physiology, on 17 September.
