Plantwise Factsheets for Farmers
Postharvest tillage against bean fly in beans
Ophiomyia centrosematis, Ophiomyia spencerella, Ophiomyia phaseoli
Recognize the problem
also called bean stem maggots (or Funza wa Maharage in Swahili), are serious
pests of all types of beans, especially common beans. A bean fly is tiny, only
about half the size of a housefly, and is shiny metallic black. Its larvae
feed into and through the leaves. They feed and tunnel down towards the stem
and stem base. They attack beans that have 2 to 3 leaves. Leaves of damaged plants
become yellow, and drop. There are also swellings and ruptures of the stem
near the ground. Because of stem destruction, plants are often stunted, wilt
and die which can cause up to 90% loss.
mostly occur during the dry season. They lay eggs on the base of both the
upper and underside of young leaves on young plants. They can lay up to 70
eggs in their 1 week lifetime. These eggs hatch into larvae after 2-4 days. Larvae
are so tiny (less than 3 mm) that they can only just be seen by eye. They
feed and tunnel inside the bean leaves and stems, which blocks water and
nutrient flow in the plant. They also pupate in the stem near the ground surface.
A complete life cycle takes 2 - 3 weeks. Thus 4 - 6 generations can develop
in one bean growing season. At the end of the season, larvae and pupae remain
in the plant stems and roots of beans and other legumes.
Some move into the soil and survive until the next bean cropping season.
post-harvest ploughing, 15 - 20 cm deep, then harrow the soil with a tractor to
facilitate the following:
- to bury the larvae, pupae and adults that are
living in the remaining bean plants, bean residues, and re-growing volunteer bean
plants after harvest. When buried deeply, they cannot survive.
- to expose larvae and pupae onto the soil
surface to be killed by the sun and eaten by birds
- Remove infested bean residues after harvest and
feed to livestock
The recommendations in this factsheet are relevant to:
Rwanda, Kenya, Zambia, Malawi, Tanzania
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