Through our feedback mechanism on the BioProtection Portal, CABI has recently discovered that growers in Kenya are experiencing problems with bean fly (Ophiomyia spp.). We have put together this information article about the fly to help you recognize it, prevent it from becoming a pest, and manage it effectively once it has become a pest.
The bean fly can be found worldwide and so the information contained within this article will be useful growers not only in Kenya but also in other countries affected by this pest.
How can you identify bean fly?
Known commonly as bean fly or bean stem maggot, this insect’s scientific name is Ophiomyia spp. including O. phaseoli, O. spencerella and O. centrosematis.
Bean fly is a small shiny, metallic bluish-black fly, about 2mm in length with clear wings. The larvae are yellow-white in colour and 3mm in length. Pupae are barrel shaped and 2-3mm long. They are initially yellow with dark ends but become dark brown (O. phaseoli) or shiny black (O. spencerella) or red-orange (O. centrosematis).
Which plants does bean fly attack?
The larvae of this small, bluish-black fly attack the stems and leaves of leguminous plants, including Common bean (Phaseolus vulgaris).
O. phaseoli is the most destructive of the group, attacking a wide range of legumes including common bean (Phaseolus vulgaris), soybean (Glycine max) and cowpea (Vigna unguiculate). O. spencerella also attacks the common bean (P. vulgaris) as well as rice bean (Vigna umbellate), Lima bean (Phaseolus lunataus) and other Fabaceae. Similarly O centrosematis has a wide host range including common bean (P. vulgaris), butterfly pea (Centrosema pubescens) and cowpea (V. unguiculata).