Recent reports were received of decidedly non-armyworm looking caterpillars attacking corn cobs in a crop near Mundubbera. The larvae in question were pale with lines of large dark spots on their back, and looked very similar to a serious mungbean pest, beanpodborer (Maruca vitrata). However, the larvae in question were slightly larger (about 20 mm) and some had a slight pink tinge.
Larva found at Mundubbera (with insert of bean podborer)
Some larvae were found at the end of the cobs, most were found tunnelling down into the cob stalk. Damage to grain was minimal, largely because the cobs were drying down as they approached harvest readiness. Consequently, spraying was not recommended because (a) the damage was uneconomic, and (b) larvae tunnelling deep in the cob stalks wold be out of reach of insecticides.
Yellow peach moth damage to cob stalk
When reared out, the moths were bright yellow with small black dots, and were identified as yellow peach moth (Conogethes punctiferalis).
Moth reared from larva (left), compared to bean podborer adult in typical pose (right)
An unusual outbreak of yellow peach moth occurred in the Lockyer Valley in 2015, where it was found tunnelling in the stems of an experimental mungbean crop (not a usual host) planted in alternating rows in a maize crop, which was also infested.
Yellow peach moth larvae in mungbean stems in 2015