Common name: Bean fly
Scientific name: Melanagromyza phaseoli, M. sojae, Ophiomyia phaseoli, O. centrosematis
Synonym: Bean stem maggot
Common bean, cowpea, mungbean, blackgram, lima bean, and soybean
Africa, Asia, Australia, and USA
Larva feeds on leaves, stems, and taproots
that lead to wilting and sometimes death of affected parts. There may be wilted or dead seedlings, and the leaves of older plants may
become yellow and stunted. In case of heavy infestation, many plants will die in the scattered areas of the field.
Insect damage on young plants is confined mostly on the main stem of the young plant just above the soil line. Plants will wilt or will eventually die if damage is severe.
The larval feeding on leaves causes holes with corresponding light-yellow spots and larval mines with silvery curved stripes. At the later stage, the damage is clearly visible as the holes and the larval mines turned dark-brown. In cases of severe attack, infested leaves become blotchy and later hang down. Infested leaves may dry-out and may eventually shed.
Insect damage on mature plants is confined to the leaf petioles
which become swollen
and at times the leaves may wilt.
When larva is about to pupate, it feeds downward into the taproot and pupates inside the stem close to the soil surface. The damaged stems are thicker than normal and they cracked lengthwise just above the soil.
The eggs are oval, clear, and milky-white in color. These are laid in holes of leaves near the petiole.
The maggot is small and white in color with brown head.
The pupa is barrel-shaped, yellow with a brownish-tinge and distinctly darker ends. It has well-defined segments with black anterior and posterior breathing organs. It becomes dark-brown before the adult emergence.
The adult has metallic-black color about Œ in size than that of a common housefly.