Scientists build resilience in beans with unique fungi

A new dose of friendly fungi could be the much awaited secret for boosting the resilience of beans and cassava to pest attacks scientists now say, a discovery that could free farmers from years of over reliance on expensive organic methods of pest control at a time when pests like mealy bug have cost Kenyan farmers upto 40 percent in yield losses.

The scientists drawn from International Center for Agriculture (CIAT) and the US Department of Agriculture intend to fight the seed-drilling bean weevil and the voracious, sap-sucking cassava mealybug by introducing a particular strain of fungus to live inside the crops.

Traditionally commercially-available fungal “bio-pesticides” have been diluted and sprayed directly onto crops or the ground around them, but farmers have been forced to apply litres and litres of it to safeguard a whole field.

This makes it prohibitively expensive for smallholder farmers, and many don’t have access to the large amounts of water required to dilute it either. For example Ecostar one of the bio pesticides commonly used in Kenya requires about 40 litres to dilute a 250mg sachet. This only covers quarter of an acre “and the impact on the control of mealybugs and other pests isnt that strong which has seen farmers poison their farms with more of these pest control pesticides when the initial application fail,”said Munene Coro a scientist with KARI.

Scientists therefore are giving the pest control method a different approach hoping to prove that the commercially-available Beauveria bassiana fungus can be transferred into bean and cassava crops. Instead of directly killing the pests, they hope to show that it will help boost the plants’ natural defences against them.

For beans, for example they scientists hope to spray the fungus onto the flowers of mother plants to see if it is passed on to the seeds. If successful, it could provide the an offspring with some level of built-in pest resistance. For cassava, which is propagated through the planting of stem cuttings from mother plants, they will spray the cuttings.

Both the flower heads and “wounds” on the stem cuttings may offer useful doorways for introducing the fungus into the plants. “It’s a similar idea to probiotic yoghurt – but for plants. You can think of it as a kind of fungal vaccination; a benevolent dose of friendly fungi,” said CIAT entomologist Soroush Parsa, the project’s principal investigator.

If it works and is rolled out officially in the market by end of 2013 according to the scientists, the friendly fungi would signify a major leap forward in the biological control of pests. By spraying the flowers or the stem cuttings just once, rather than whole fields several times, farmers will only need to use a fraction of the amount of fungus in order to achieve field-wide resistance. That also makes it much cheaper and potentially much more effective.

Mealybugs damage plants by sucking sap from roots, tender leaves, petioles and fruit. They excrete honeydew on which sooty mould develops. Severely infested leaves turn yellow and gradually dry. Severe attack can result in shedding of leaves and inflorescences, reduced fruit setting and shedding of young fruit. The foliage and fruit may become covered with sticky honeydew, which serves as a medium for the growth of sooty moulds. It affects almost all horticultural produces and cassava